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CLIENT PROJECT REPORT CPR1801 New UN regulation on child restraint systems - assessment of amendments to the new regulation, front and side impact procedures and Q-Series dummy family injury criteria Final report C Visvikis, M Pitcher, J Carroll, R Cuerden, A Barrow

Prepared for:

European Commission, DG Enterprise

Project Ref:

Specific Contract No. SI2.630806

Quality approved: Mike Ainge

Jolyon Carroll

(Project Manager)

(Technical Referee)

© Transport Research Laboratory

Disclaimer This report has been produced by the Transport Research Laboratory under a contract with the European Commission. Any views expressed in this report are not necessarily those of the European Commission. The information contained herein is the property of TRL Limited and does not necessarily reflect the views or policies of the customer for whom this report was prepared. Whilst every effort has been made to ensure that the matter presented in this report is relevant, accurate and up-to-date, TRL Limited cannot accept any liability for any error or omission, or reliance on part or all of the content in another context. When purchased in hard copy, this publication is printed on paper that is FSC (Forest Stewardship Council) and TCF (Totally Chlorine Free) registered.

Document amendment record This is a revised document with minor editorial corrections, dated 10th July 2014.

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CPR1801 - New UN regulation on child restraint systems

Contents 1

2

Introduction

1

1.1

Background

1

1.2

Project scope and approach

2

Non-integral child restraint systems: performance criteria and test methods 2.1

2.2

Performance of non-integral child restraint systems in collisions and priorities for protection

4

2.1.1

Review of European studies

4

2.1.2

Analysis of in-depth representative collision databases

8

Tools and methods for assessing the performance of non-integral child restraint systems 2.2.1 2.2.2

2.3

3

Q-Series interaction with the diagonal belt

16 19

Review of regulatory and consumer test procedures for vehicle safety

20

2.3.2

Review of literature

22

2.3.3

Summary

24 25

The test pulse for frontal impact

27

3.1

Overview

27

3.2

The characteristics of frontal impact collisions involving children

28

3.2.1


28

3.2.2


30

3.4

Comparison of vehicle and sled pulse characteristics and their effects

31

3.3.1

Pulse comparison

31

3.3.2

Effect of pulse differences on dummy loading

32

Regulatory implications

32

Applying injury criteria for the Q-Series

34

4.1

Injuries to children and priorities for protection

34

4.1.1


34

4.1.2


35

4.2

4.3

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11


3.3

4

10

Q-Series lap belt interaction and implications for abdomen injury assessment

The protection of children by vehicle safety features 2.3.1

2.4

4

Review of Q-Series injury criteria and performance limits

36

4.2.1

Analysis of available criteria and limits

36

4.2.2

Proposals for chest deflection thresholds

39


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5

The side impact test procedure

42

5.1

Overview

42

5.2

Vehicle and sled impact conditions and their effects on dummy loading

42

5.2.1

Comparison of pulse and intrusion characteristics

43

5.2.2

Comparison of dummy loading

43

5.3 5.4 6

Sensitivity of the side impact test procedure to child restraint differences

45


47

Conclusions 6.1

49

Non-integral ISOFIX child restraint systems: performance criteria and test methods

49

6.2


50

6.3


50

6.4

The side impact test conditions

51

References

52

Annex 1


56

Annex 2

Q-Series lap belt interaction and implications for abdominal injury assessment

97

Annex 3

Q-Series diagonal belt interaction and implications for chest injury assessment

135

Annex 4

Comparison of vehicle and sled front impact pulse characteristics and their effects

154

Annex 5

Practical investigation of side impact pulse and intrusion characteristics

167

Annex 6

Sensitivity of side impact test procedure to differences in child restraint system quality

182

Annex 7


197

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Executive summary This report was prepared for the European Commission’s Directorate-General for Enterprise and Industry. It was completed during the development of Phase 2 of United Nations (UN) Regulation 129 on “Enhanced Child Restraint Systems”. In this phase, the regulation was amended to incorporate non-integral child restraint systems (alongside integral ISOFIX child restraints). The main aim of the research that this report describes was to support the Commission during the development of the regulation, and to generate the evidence-base from which to make decisions about the performance requirements and test procedures. The following subsections of this executive summary follow the principal topic areas of the research.

Non-integral child restraint systems: performance criteria and test methods Injuries to children in non-integral child restraint systems tend to occur in the head, chest and abdomen (in both front and side impact collisions); however, we found there were insufficient representative data to identify specific priorities or to assess the benefits of intervention. Given that UN Regulation 44 assesses child restraints in these body regions (in front impact), it seems reasonable to do so in UN Regulation 129. However, simply adopting the front impact test procedure from UN Regulation 44 and replacing the P-Series with the Q-Series (albeit with a new test bench) may not deliver significant improvements in the performance of non-integral child restraints, and may even have a detrimental effect. This is due to the interaction between the Q-Series dummy and the three-point seat belt. Our experiments highlighted two phenomena (that have also been described extensively elsewhere): i.

Penetration of the lap part of the seat belt into the gap between the legs and the pelvis (and its implications for the assessment of abdomen injury protection);

ii.

Movement of the diagonal part of the seat belt towards the neck (and its implications for the assessment of head displacement and chest injury protection).

Although we found that the interaction between the dummy and the lap belt could be improved (by accessories to prevent belt intrusion and by set-up positioning), the test procedure may not encourage features that keep the belt low on the pelvis (such as a raised seating position and/or lap belt guides). Similarly, movement of the diagonal part of the belt towards the neck reduces the contribution made by the child restraint in keeping the child within the belt and reduces the value of the chest deflection sensor (in its present position).

The test pulse for frontal impact Our analysis of in-depth representative collision databases showed that the front impact pulse in UN Regulation 129 is set at an appropriate velocity for the majority of collisions that children are involved in. However, the sled deceleration profile no longer represents that of a modern car in a ‘full-width’ collision. Defining a sled deceleration corridor in UN Regulation 129 that reflects the deceleration pulse of a car in a full-width collision would be appropriate; not only to test child restraints under worst-case conditions, but also in a common collision scenario (as our analysis revealed).

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The current corridor underestimated the passenger compartment deceleration in a fullwidth car-to-car experiment with a typical supermini. It also underestimated the dummy head and chest acceleration, such that the regulatory performance limits were exceeded in the car-to-car experiment, but not in comparable sled experiments (with the same child restraints, performed to the regulatory test procedure). An alternative corridor (proposed by TRL in a previous research project for the Commission) was capable of representing the passenger compartment deceleration of modern cars and reproduced the dummy loading more accurately than the current corridor.

Applying injury criteria for the Q-Series UN Regulation 129 captures important body regions to protect for children in child restraint systems. With regards to front impact, these comprise the head and chest only, although neck forces and moments are recorded “for monitoring purposes”. Neck injuries appear to be rare, but it is important this monitoring takes place (and is coordinated among approval authorities) to guard against load transfer from other (regulated) body regions. Two potentially important parameters are not included; chest deflection and abdomen pressure. Specifying performance thresholds for these parameters would prevent (excessive) concentrated loads being applied to the torso of the dummy to reduce head and chest acceleration (for which thresholds are applied). Specifying side impact performance thresholds for the head is likely to target the most severe injuries that children receive. However, serious injuries occur in other body regions. At present, there are insufficient representative data to comment meaningfully on the distribution of injuries by body region in side impact collisions, but injuries are observed in the chest and abdomen (including the pelvis). Very few data are available with which to derive injury-based performance thresholds for other body regions in side impact. In the meantime, deriving pragmatic limits based on improving the worstperforming child restraints on the market would provide an alternative solution.

The side impact test procedure The side impact test procedure provides a reasonable approximation of the struck door intrusion velocity during the period of maximum loading to a child’s head in a side impact collision. We found that the test procedure replicated the head kinematics and loads from a full-scale side impact experiment (between two identical supermini cars in a perpendicular collision). However, the flat profile of the intrusion surface in the regulatory test seemed to favour head containment, whereas the more dynamic nature of real vehicle intrusion seemed harder to manage, particularly for the forward-facing child restraint system used in our experiment (although the dummy’s head was ultimately contained). The procedure appeared to be a stringent test of the capacity of rear-facing child restraints to manage head loading. However, there was less evidence (in our experiments) that the procedure would encourage features for side impact protection in forward-facing child restraints. In fact, our results demonstrated that it was possible to degrade features that were expected to be of benefit in side impact crashes, but still meet the requirements of UN Regulation 129. This was based on experiments with a Q3 dummy; it is possible that the outcome would have been different if the Q1.5 dummy had been used (because its head would be closer to the intrusion panel).

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1 1.1

Introduction Background

The use of a child restraint system is mandatory when travelling in cars (or goods vehicles) in all Member States of the European Union, in line with Directive 91/671/EEC, as amended by 2014/37/EU. The Directive requires that children less than 150 cm in height are restrained by a child restraint, approved to UN Regulation 44.03 or UN Regulation 129 (or subsequent adaptations to these regulations). Certain exemptions are provided for special categories of vehicles, such as taxis, and Member States are permitted to mandate the use of child restraints for children up to 135 cm in height, rather than 150 cm, if they wish.

This report sets out the findings from a project

undertaken

to

support

the

European Commission during Phase 2 of the development of the new United Nations (UN)

Regulation

on

“Enhanced

Child

Restraint Systems” – UN Regulation 129. The principal aims of the project were to review the outputs of the UN Informal Group responsible for developing the new regulation,

and

where

necessary,

to

generate the evidence-base from which to make

recommendations

for

the

way

forward.

UN Regulation 44 specifies performance requirements for child restraints used in powerdriven vehicles. It includes front and rear impact tests with the P-Series “family‟ of child dummies. The UN Regulation has undergone four revisions since it was introduced in 1981, although there have been no major safety-related changes (i.e. to the type and stringency of the test procedures). In 2007, the UN Informal Group on Child Restraint Systems was established by the Working Party on Passive Safety (GRSP) to develop a draft new UN Regulation on the approval of “Enhanced Child Restraint Systems”. It was envisaged that UN Regulation 44 would remain valid during the implementation phase of the new regulation. The Informal Group is undertaking its work in three phases. Phase 1 was completed as a draft regulation in 2011 and came into force as UN Regulation 129 on 9 July 2013. It sets out performance requirements and test methods for integral ISOFIX child restraint systems, in which the child is restrained by means of a harness or shield that is coupled to a supplementary child seat. In addition, it introduces the “i-Size” concept for child restraint to car compatibility, a stature-based system of classification (for child restraints), a new family of child dummies (the Q-Series) and a side impact test procedure. The Terms of Reference for Phase 2 and Phase 3 were agreed by GRSP in 2011, and were recently amended to extend the mandate of the Informal Group to December 2014. The extended mandate sets the completion date for Phase 2 to May 2014. For this phase, the Informal Group is required to extend UN Regulation 129 to include nonintegral child restraint systems, which position the child to improve the fit of the adult seat belt. The Terms of Reference also require the Group to review the test pulse for front impact as well as the application of injury criteria for the Q-Series (for all impact directions).

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The new UN Regulation is intended to deliver “Enhanced Child Restraint Systems” that are superior to those currently on the market. It is essential, therefore, that any new procedures and requirements introduced by the new Regulation are validated fully with robust supporting evidence. This will ensure that the levels of safety envisaged by GRSP are achieved and will benefit stakeholders and citizens of the European Union (and any other regions that adopt the Regulation).

1.2

Project scope and approach

The Terms of Reference of the UN Informal Group on Child Restraint Systems were used as a starting point in considering what research was needed to complete the final phases of UN Regulation 129. The Terms of Reference stated that Phase 2 would: i.

ii.

iii.

During the course of this project, the UN Informal Group proposed not to restrict Phase 2 of UN Regulation 129 to nonintegral

child

attachments.

restraints This

with

ISOFIX

stemmed

from

difficulties in agreeing a universal ISOFIX

Develop definitions, performance criteria and test methods for non-integral child restraint systems with ISOFIX attachments;

solution among the stakeholders (and the observation that ISOFIX may not offer performance advantages for these child restraints

Review the test pulse for frontal impact (increased severity and child restraint integrity check) in the light of recent accident data;

or

reduce

Notwithstanding

the

described

this

here,

their project report

misuse). scope aims

to

consider all non-integral child restraints in light of the proposal made by the Informal Group.

Review the strict application of recognised and accepted injury criteria related to the new generation baby/child crash test Q-dummies, as supported through EEVC and other EU research programs, in the light of recent accident data.

The final two points were included in the Terms of Reference at the request of the Commission, with the support of a number of Member States and other stakeholders. However, it was understood that any proposals to amend these aspects of the new regulation would need to be accompanied by robust supporting evidence. The Commission also considered that there was added value in research to make a ‘final’ assessment of the side impact test procedure, to verify that it was broadly representative of a real collision and capable of distinguishing differences in child restraint system design. However, it was recognised that this did not form part of the Terms of Reference and there was no obligation on the Informal Group to explore side impact further. This report evaluates some of the issues raised by the Terms of Reference of the UN Informal Group, as well as the side impact procedure and presents the findings of a research project undertaken by TRL for the European Commission. It is arranged according to four key topic areas (dictated by the Terms of Reference) and considers: i.

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How the test parameters might need to be amended to accommodate nonintegral ISOFIX child restraint systems, including any particular aspects of their performance that might need to be addressed;

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ii.

Whether the front impact pulse should be updated to reflect modern vehicles and the type of collisions that children are involved in;

iii.

How best to apply recognised and accepted injury criteria related to the Q-Series dummy family;

iv.

How well the side impact test procedure represents the essential characteristics of real side impact collisions and distinguishes between child restraints with different levels of side impact protection.

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2

Non-integral child restraint systems: performance criteria and test methods

Non-integral child restraint systems raise the child to improve the fit and position of the adult seat belt over the child’s body. They also allow a child to bend their knees, which depending on their stature, may be impossible when they sit directly on a car seat (unless they adopt a slouched posture, which can result in pelvis rotation rearwards and potentially a greater risk of the seat belt slipping off the iliac crests). Non-integral child restraints may provide an added benefit, therefore, which is to encourage a child to sit up straight with their back against the seat back, thereby maintaining their pelvis at an ideal angle (Klinich et al., 1994, Jakobsson et al., 2011). Many non-integral child restraint systems feature guides that help to keep the lap part of the seat belt over the top of the child’s thighs and away from their abdomen. Some also include a backrest that supports the child and provides a guide for the diagonal part of the seat belt, which helps to improve fit and reduce head excursion. These are commonly known as booster seats, and can provide protection in a side impact collision by containing the child and shielding them from vehicle intrusion. Phase 2 of the development of UN Regulation 129 will introduce non-integral child restraint systems. The regulation will need to be amended, therefore, to include definitions, performance criteria and test methods for these child restraints. These amendments will be prepared by members of the UN Informal Group, and will need to draw from the latest collision data analyses to ensure that the performance evaluation of non-integral child restraints is targeted appropriately. This chapter summarises our research to examine how the test parameters might need to be amended to accommodate non-integral child restraints. It comprises three main parts: the first investigates the performance of non-integral child restraints in collisions; the second reviews the tools and methods available for assessing the performance of non-integral child restraints; and the final part examines the compatibility of vehicle safety systems with children and the need for dedicated child restraint systems.

2.1


Non-integral child restraint systems reduce the risk of injury compared with adult seat belts, particularly for children that have outgrown integral child restraints (Arbogast et al., 2009). Nevertheless, it appears that some children are killed or seriously injured in non-integral child restraints during collisions they might reasonably be expected to survive with moderate injuries (Jermakian et al., 2007). Furthermore, impact experiments with a cross-section of non-integral child restraints suggest very different levels of protection might be provided to children, and these do not necessarily correlate with the cost of child restraints (Hynd et al., 2010). 2.1.1


The outputs from four key (European) groups are used here to illustrate the performance of non-integral child restraint systems in collisions; however, it is recognised that UN Regulation 44 has been adopted in other regions and that UN Regulation 129 may also be adopted in these regions too. These groups comprise:

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i.

Working Group 18 (Child Safety) of the European Enhanced Vehicle Safety Committee (EEVC) reviewed a broad range of representative as well as nonrepresentative collision databases from around Europe. The work was described by EEVC WG18 (2008).

ii.

EEVC Working Groups 12 (Biomechanics) and 18 (Child Safety) collaborated on joint research to support the development of the Q-Series dummy. The work was described by Wismans et al. (2008), which incorporated the findings of EEVC WG18 (2008), with additional analyses.

iii.

EPOCh (Enabling Protection for Older Children) was a collaborative European project of the 7th Framework Programme (FP7) undertaken to develop a prototype 10/12 year old Q-Series dummy. The project included an analysis of the United Kingdom Cooperative Crash Injury Study (for the period 1998 – 2008). The work was described by Visvikis et al. (2009) and comprised older children only (aged 6 to 12 years).

iv.

CASPER (Child Advanced Safety Project for European Roads) was another collaborative European project of the 7th Framework Programme. One of the main activities of CASPER was to perform accident reconstruction experiments to support the development of injury risk curves for the Q Series dummy. Cases for reconstruction were selected from a large database of collisions collected during the project and during its predecessors, CHILD and CREST. Further deliverables are likely to emerge from CASPER, but in the meantime, the collision database was described by Kirk (2012) and by Lesire (2012).

Table 1 and Table 2 summarise the findings from these groups for children in nonintegral child restraint systems. They set out the body regions that are typically injured and the key injury mechanisms, and are presented here to highlight what is known about the nature of injuries to children in these restraints.

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6

Reduce fatalities and injuries to children in traffic accidents

CASPER

(includes CHILD)

Review accident data on older children

Identify causes of injury to children in front impacts based on real world data

EEVC WG12 & WG18

EPOCh

Review data on children and their injuries in all types of accidents

Objective

EEVC WG18

Group

2009 – 2012 (data back to 2000s)

Abdomen is most injured at AIS≥4 (10%), followed by head and thorax (7% each)

Two mechanisms proposed for abdomen injuries: loading from lap part of adult seat belt (due to poor initial position or rotation of pelvis under belt); and loading to upper abdomen from diagonal part of seat belt (due to sliding or poor belt path) AIS≥2 injuries tend to be evenly distributed, but extremities is most injured (23%) followed by abdomen (20%), head (16%) and thorax (15%)

129 children in non-integral child restraints

Boosters (seats and cushions)


The most common abdomen injury mechanism is seat belt loading at the site of the injured organ (due to poor initial position of belt, and/or pelvis slipping under belt)

(cases supplied by project partners)

Three children with AIS≥2 injuries (head x 2 and neck)

Multiple

Known use of nonintegral child restraints very low (23%; n=23)

Summarising literature only, the authors note that head and extremity injuries are caused principally by contact with vehicle interior

No AIS≥2 injuries in sample

277 children aged 6 – 12 years

(data spans 1998 –2008) Booster cushions

Older children (regardless of restraint type)

Booster seats

Authors attribute greater frequency of chest injuries to older children (less flexible chests), implying such injuries are predominantly fractures

Booster cushions

CCIS (UK)

Frequency of chest injuries increases compared with booster seats

Authors note that chest injuries occurring without rib fracture, due to flexibility of chest in children

Similar comments as those above for abdomen injuries

Booster cushions

Booster seats

As above, with authors adding that limb fractures are frequent, but “not a priority for the moment “

Mechanisms not discussed in detail, but penetration of seat belt into soft abdominal organs noted for abdomen injuries

All non-integral child restraints

Key mechanisms

Booster seats

Chest not a priority (for frequency) but important due to vital organs

No specific data presented across all sources; but authors highlight head (for frequency) as well as abdomen

All non-integral child restraints (Booster seats AND cushions)

Body regions

2009 – 2011

(includes data from 1990s)

Multiple, as above (same sources)

(IRTAD; CREST; CHILD; CCIS; UK Questionnaire; CSFC-1996; GIDAS; GDV; CASIMIR)

2008

Multiple


Sources

2001 – 2006

Study period


Table 1: Summary of studies on injuries to children in non-integral child restraint systems: front impact

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Identify causes of injury to children in front impacts based on real world data

Review accident data on older children

Reduce fatalities and injuries to children in traffic accidents

EEVC WG12 & WG18

EPOCh

CASPER

(includes CHILD)

Review data on children and their injuries in all types of accidents

Objective

EEVC WG18

Group

2009 – 2012 (data back to 2000s)

127 children aged 6 – 12 years

(data spans 1998 –2008)

Head is most injured body region at AIS≥4 (44%) followed by thorax (9%)

Head is most injured body region at AIS≥2 (65%), followed by extremities (26%), abdomen and thorax (17% each)

(cases supplied by project partners)

No AIS≥2 injuries in non-integral child restraints, but too few cases to draw conclusions


129 children in non-integral child restraints

No significant discussion of injury mechanisms

Key mechanisms

Injury mechanisms in side impact not reported yet by CASPER, but CHILD project indicates impact with rigid part of car for head injury, and intrusion of vehicle structure for chest and abdomen injuries

Summarising literature only, the authors note that the principal mechanism for head injuries is contact with the vehicle interior (with and without intrusion)

Older children (regardless of restraint type)

No side impact analysis; study objectives focussed on front impact only

Injuries to chest and abdomen occur also, particularly with booster cushions

Limited data available to authors of study; but, they highlight head as a priority regardless of child restraint type

Body regions

Multiple

Known use of nonintegral child restraints very low (6%; n=8)

CCIS (UK)

2009 – 2011


Multiple, as above (same sources)

(IRTAD; CREST; CHILD; CCIS; UK Questionnaire; CSFC-1996; GIDAS; GDV; CASIMIR)

2008

Multiple


Sources

2001 – 2006

Study period


Table 2: Summary of studies on injuries to children in non-integral child restraint systems: side impact

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Front impact With regards to front impact, the consistent message across these sources is that injuries to children in non-integral child restraints tend to occur to the head, abdomen and the extremities. Contact with the vehicle interior appears to be the principal injury mechanism for head and extremity injuries, whereas the abdomen is injured by loading from the adult seat belt. Injuries to the chest are less common, as are neck injuries, which appear to be particularly rare. At present, UN Regulation 44 applies performance requirements to the (P-Series) dummy head excursion, chest acceleration and abdomen loading (by means of a clay insert between the lumbar spine and the foam abdomen block). These studies indicate that it would be desirable to maintain the assessment of child restraint system performance at these body regions in UN Regulation 129. Additional assessment of the risk to extremities would appear to be supported by data from these sources; however, the role of vehicle intrusion in these injuries needs to be understood more fully before additional requirements are placed on child restraint systems (such as foot or ankle excursion, for example). Also the validity, robustness, repeatability and reproducibility of using such measurements would need to be confirmed before implementation. None of the studies indicate that neck injury protection in child restraint systems needs to be enhanced. Nevertheless, adopting neck performance requirements in UN Regulation 129 might be useful to prevent the neck from being loaded improperly (to reduce loads to other body regions). Side impact Fewer data were generally available from side impact collisions, but injuries to children in non-integral child restraints typically occur to the head, chest and abdomen. The principal mechanism for these injuries is contact with the interior of the vehicle, in areas with intrusion as well as areas with no intrusion. UN Regulation 44 does not assess the performance of child restraints in side impact collisions, although requirements are placed on the depth of the side wings in rear-facing child restraints. UN Regulation 129 introduces a side impact test for child restraint systems and the data from these studies suggest that the assessment of non-integral child restraints should cover these three areas of the body. 2.1.2


Section 4 in Annex 1 describes a case-by-case review of collisions with injured children in non-integral child restraint systems. In-depth field data were used to investigate injury mechanisms and possible countermeasures that could be implemented in legislation such as UN Regulation 129. Ten cases were found that met the inclusion criteria: MAIS≥2 injuries, using a non-integral child restraint in a front impact collision. These are summarised in Table 3. The review focused on front impact because only one side impact case was found in the in-depth databases from Great Britain and Germany1.

1

This involved a brain injury to a four year old child seated in a booster cushion in a struck side impact.

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Table 3: Case-by-case review of injured children in non-integral child restraint systems (front impact collisions) Injury description and mechanism

Velocity change (km/h)

Overlap (%)2

Booster cushion

32

100

Head

2

Deep face laceration

Contact with the front seat-back

5

Booster seat

35

48

R arm

2

Fore-arm fracture

Contact with vehicle interior

3

6

Booster seat

39

100

L leg

3

Lower leg fracture

2

Lower leg fracture

4

3

Booster seat

-

65

Head

2

Skull fracture

Neck

4

Fracture/dislocation

7

Booster cushion

Abdomen

2

Intestinal contusion

Pelvis

2

Iliac wing fracture

L Arm

2

Clavicle fracture

Thorax

3

Lung contusion

2

Skull fracture

2

Brain injury


Abdomen

2

Liver contusion

Seat belt webbing

Arm

2

Clavicle fracture

Abdomen

3

Abdominal vein injury

Head

5

Brain injury

Neck

2

Vertebra fracture

Arm

2

Clavicle fracture

Thorax

4

Lung contusion

2

Liver laceration

2

Kidney rupture

2

Pancreas rupture

2

Brain injury

Case#

Age (years)

1

8

2

5

6

7

8

9

Child restraint

5

Booster seat

3

Booster seat

6

5

Booster seat

Booster seat

-

59

40

68

94

29

100

63

47

47

Body region

Head

Abdomen

10

5

Booster Cushion

26

96

Head

AIS

Injury

Injury mechanism

Contact with facia panel Contact with intruded B-pillar Seat belt webbing with possible misuse of diagonal belt Seat belt webbing

Seat belt webbing Contact with the front seat-back

Seat belt webbing


Head injury resulting from contact with the interior of the vehicle was the most common mechanism of injury for children in non-integral child restraints, although the number of cases available for analysis was quite low. This included collisions that seemed to be less severe than the front impact test in UN Regulation 44 and that involved cars with plenty of ‘excursion space’ in front of the child. There are two possible explanations for head injury in these circumstances: i.

The child restraint systems were misused in a way that caused high head excursion (but was not detected by the retrospective collision investigations);

ii.

The regulatory test of the child restraints underestimated head excursion in the real-world collisions.

Also present, were injuries to the shoulder and chest that were caused by the forces in the three-point seat belt in severe front impact crashes (60 – 70 km/h, velocity change).

2

Percentage of direct contact damage to front structure of the car

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Assuming that the non-integral child restraints were used correctly, and already provided an optimum belt path, there may be limited scope for further improvement, even if the test severity was increased to match these collisions. Nevertheless, with no vehicle intrusion (adjacent to the children) and no head contacts, these injuries might have been mitigated by more advanced vehicle seat belts that were tailored to these occupants. Injuries to the abdomen were also observed in our sample, although their frequency was biased somewhat by one child that received three abdominal injuries in a very severe crash. There were too few cases to distinguish any trends in the type or location of abdominal injuries. Clearly, with so few cases available for analysis, it is difficult to draw firm conclusions about the size of any ‘problem’ for any of the injuries discussed above. Improving the provision of representative data for children would allow the situation to be monitored more closely and for legislative actions to be targeted for the greatest benefits (in terms of injury reduction).

2.2

Tools and methods for assessing the performance of non-integral child restraint systems

The P-Series were the most sophisticated child dummies in Europe when UN Regulation 44 was introduced. They have been instrumental in improving the quality of child restraints and have proven extremely durable for regulatory testing. Nevertheless, the dummies are relatively simple load measuring devices. The anatomy and behaviour of the internal structures of the body are not represented, which is one of the fundamental shortcomings of the dummy. In addition, the method it uses to detect abdomen loading (a clay insert) is somewhat subjective and does not allow for a complete assessment of injury risk. UN Regulation 129 introduces the Q-Series family of child dummies. These dummies were designed to be more advanced than the P-Series and have been evaluated comprehensively by EEVC Working Groups 12 and 18 and in European Framework projects (most recently, CASPER and EPOCh). These studies typically conclude that the dummy is ready for use in legislative (as well as consumer) testing (see Wismans et al, 2008; Hynd et al, 2011). The Q-Series do not meet all of their targets for biofidelity (Visvikis et al., 2008). However, there were designed to be omnidirectional dummies that are capable of being used in both front and side impact. Tuning the dummies for one direction could affect their performance in the other direction, and hence a balance between the two was sought (Hynd et al., 2011). Side impact versions of the Q3 and the Q6 dummies have been developed that feature a more compliant shoulder and chest (amongst other developments), but they are not being considered for use in UN Regulation 129. The Q-Series are expected to help bring about a step forward in the protection of children in cars. Nevertheless, possible shortcomings were highlighted during the CASPER project (Beillas and Alonzo, 2010). Arguably the most significant, particularly for the assessment of non-integral child restraint systems are: i.

Penetration of the lap part of the seat belt into the gap between the legs and the pelvis (and its implications for the assessment of abdomen injury protection);

ii.

Movement of the diagonal part of the seat belt towards the neck (and its implications for the assessment of head displacement and chest injury protection).

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In each case, these phenomena occur regardless of the characteristics, or even presence, of the non-integral child restraint system. They have the potential, therefore, to reduce the capacity of UN Regulation 129 to improve (or perhaps even maintain) the performance of non-integral child restraints. A pragmatic approach may be needed to satisfy the needs of the regulation (and the timescales dictated by the Terms of Reference of the Informal Group). For instance, taking steps to reduce the effects of these shortcomings by applying accessories to the dummy, and/or specifying other solutions in the test procedure, might help to avoid the need for further developments in the design of the dummy. 2.2.1

Q-Series lap belt interaction and implications for abdomen injury assessment

Annex 2 describes a programme of experiments undertaken to study the interaction between the Q-Series dummies and the lap part of the seat belt in UN Regulation 129 front impact tests. The dummies (a Q3 and a Q10) were equipped with prototype abdominal sensors loaned to TRL by IFSTTAR and described by Beillas (2012). The dummies were restrained in non-integral ISOFIX child restraints under various different conditions. A summary of the main findings is provided below. Effects of abdominal sensors on dummy response Previous studies have observed that the prototype abdominal sensors do not influence the broader response of Q-Series dummies (in quasi-static tests) (Beillas et al., 2012). However, less research has been published about their effects on the Q10. Figure 1 shows that the sensors had marginal effects on the response of the Q10 in our experiments. Lumbar spine flexion (observed from the posture of the dummy in Figure 1) and peak head excursion may have reduced when the sensors were fitted, but the evidence for a trend was fairly weak. Reducing head excursion would, in principal, be an undesirable effect (unless it can be demonstrated to improve biofidelity) because it might mean that a child restraint system passes the test, when it might otherwise fail. In this instance, the Q10 head excursion was well within the limit specified in UN Regulation 129 in both experiments.

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No sensors

With sensors Figure 1: Effects of abdominal sensors on Q10 belt interaction and other sensor measurements Effects of accessories to prevent lap belt intrusion on dummy response The pelvis inserts developed for the Q3 reduced belt intrusion, but did not prevent it entirely. This is illustrated in Figure 2, which shows that the belt was more visible over the dummy when the inserts were used. Nevertheless, part of the belt intruded into the gap between the legs and the pelvis. The pelvis inserts had no (unintended) effects on the main dummy measurements. The abdomen pressure reduced markedly when the inserts were used, but the abdomen did not undergo significant loading in either experiment and hence these differences might not be important.

No pelvis inserts

With pelvis inserts Figure 2: Effect of pelvis inserts on Q3 kinematics and belt interaction Belt intrusion was more marginal with the Q10 (than with the Q3); nevertheless, the belt was higher on the pelvis (with much less abdominal expansion) when hip shields were used with the dummy. This is illustrated in Figure 3, which also shows that the dummy

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measurements tended to increase when the hip shields were used. It was unclear why they might have such an effect; no additional slack was introduced into the belt, for instance.

No hip shields

With hip shields Figure 3: Effect of abdomen sensors and hip shields on Q10 kinematics and belt interaction Sensitivity of the UN Regulation 129 front impact test procedure to child restraint features for abdominal protection The front impact test procedure in UN Regulation 129 did not distinguish between two non-integral child restraints with seemingly different characteristics for abdominal protection. This is shown in Figure 4 with the Q3 and in Figure 5 with the Q10. The two child restraints performed equally regardless of the presence of guides to position the lap part of the belt and keep it in place. This is shown from the position of the belt and from the abdominal pressure measurements in the Figures. Both child restraints met the requirements of UN Regulation 44 and hence significant abdominal loading was not expected. Nevertheless, it may be desirable for UN Regulation 129 to encourage enhanced features for abdominal protection in child restraint systems. Lap belt guides are an example of such features and would be expected to improve the performance of child restraints in the field (although it is difficult to prove this from existing field data). The test procedure was capable of distinguishing between the characteristics of integral child restraints with impact shields and those of non-integral child restraints. This is shown in Figure 4. The abdominal pressure measurements were much higher with impact shields and exceeded the threshold proposed for the Q3 by Johannsen et al. (2012b).

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No lap belt guides

Lap belt guides Figure 4: Sensitivity to child restraint features with the Q3

No lap belt guides

Lap belt guides Figure 5: Sensitivity to child restraint features with the Q10 Effects of ISOFIX on non-integral child restraint performance The use of ISOFIX attachments did not improve the performance of the non-integral child restraint system used in these experiments. This is shown in Figure 6 with the Q3 and in Figure 7 with the Q10. Although this was based on one (representative) product only, it appears that including non-integral child restraints without ISOFIX in UN Regulation 129 would not have any detrimental effects on the safety of older children that use these child restraints.

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Belt only

ISOFIX Figure 6: Effect of ISOFIX on Q3 dummy and belt interaction

Belt only

ISOFIX Figure 7: Effect of ISOFIX on Q10 dummy and belt interaction Effects of test procedure aspects on dummy interaction with the lap belt Figure 8 (with the Q3) and Figure 9 (with the Q10) show the effects of two changes to the test procedure that were examined for their potential to increase the contribution of the child restraint in keeping the belt on the pelvis: adjusting the seat cushion angle (from 15°) to 5°; and installing the dummy using a seating procedure adapted from that developed by the University of Michigan Transportation Research Institute (UMTRI) for the United States (US) Federal Motor Vehicle Safety Standard (FMVSS) No. 213. The Figures show that reducing the angle of the seat cushion to 5° did not influence the interaction between the dummy and the seat belt. There was no indication that a child restraint would need enhanced characteristics, if this angle was introduced in UN Regulation 129. However, the seating procedure adapted from UMTRI, which featured reduced belt tension and a spacer between the dummy and the child restraint, TRL

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caused the lap belt to rest higher on the pelvis of the Q3 dummy. This is shown in Figure 8. This might indicate that the influence of the test procedure in keeping the belt on the pelvis was reduced to some extent at least.

UN Regulation 129 baseline

Seat cushion at 5°

Seating procedure adapted from UMTRI

Figure 8: Effects of test procedure aspects on Q3 kinematics and belt interaction

UN Regulation 129 baseline

Seat cushion at 5°

Seating procedure adapted from UMTRI

Figure 9: Effects of test procedure aspects on Q10 kinematics and belt interaction 2.2.2

Q-Series interaction with the diagonal belt

Annex 3 describes a programme of experiments undertaken to study the interaction between Q-Series dummies and the diagonal part of the seat belt in UN Regulation 129 front impact tests. The experiments investigated potential influences on belt movement towards the neck and the implications of such movement for the measurement of chest deflection. A further experiment was undertaken to investigate the feasibility of fitting a second chest deflection sensor (to measure deflection when the belt has moved towards the neck). Effect of upper anchorage position and suit friction on belt path The diagonal part of the seat belt moved towards the neck in all of the experiments. Moving the upper anchorage position or adapting the surface friction of the dummy’s suit did not have any significant effects on the interaction between the dummy and the belt. This is shown in Figure 10 with the Q3 and in Figure 11 with the Q6. The belt moved early in each experiment, typically reaching the neck by 60 ms from the onset of the sled deceleration.

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Standard upper anchorage position

Downward 75 mm

Outboard 50 mm

Outboard 100 mm and downward 75 mm

T-shirt over suit (standard anchorage)

Friction surface on suit (standard anchorage)

Figure 10: Q3 dummy interaction with the diagonal part of the seat belt

Standard upper anchorage position

Downward 75 mm

Outboard 100 mm and downward 75 mm

T-shirt over suit (standard anchorage)

Outboard 100 mm

Figure 11: Q6 dummy interaction with the diagonal part of the seat belt The belt moved away from the chest deflection sensor, which was labelled with a red sticker in Figure 10 and Figure 11. Although the loading point and the measurement point were connected by the rib cage, the dummy did not seem to measure deflection in TRL

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the region that was being loaded by the belt. The effects on the chest deflection response are shown in Figure 12. The chart on the left shows the measurements with the Q3 and the chart on the right shows those with the Q6. Both charts display two phases; an initial peak that reflects the loading from the seat belt, followed by a larger peak that coincides with peak forward and downward flexion of the neck, with the chin loading the chest directly above the deflection sensor. This is illustrated in Figure 13, which shows experiments with the standard anchorage position as examples of this loading. Each image coincides with the main peak in the deflection response and shows the extent of loading from the chin.

Q3 dummy

Q6 dummy Figure 12: Chest deflection

Q3

Q6

Figure 13: Chest loading (standard upper anchorage) The experiments suggest that it is unlikely to be possible to prevent the belt from moving towards the shoulder with simple changes to the front impact test procedure in UN Regulation 129. With the present arrangement, very little contribution is required from non-integral child restraints in keeping the dummy within the belt and minimising head excursion. In addition, the belt loads the dummy in a region that is displaced from the deflection sensor. Effect of a second chest deflection sensor on chest injury assessment Figure 14 compares deflection measurements in the experiment with a second sensor installed in the upper chest of the Q6. The original sensor, which is located in the centre TRL

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of the chest underestimated deflection due to the belt by around 5 mm. Although the overall peak deflection was comparable between the sensors, the second peak in the original sensor occurred under loading from the dummy’s chin, as observed in the experiments described in the previous subsection. The loading to the dummy’s chest in this experiment is shown in Figure 15.

Second sensor integration Figure 14: Q6 chest deflection with second deflection sensor (standard upper anchorage)

t = 65 ms

t = 110 ms

Figure 15: Q6 dummy chest loading with second deflection sensor (standard upper anchorage) It may not be possible (at least with the present dummy design) to prevent the belt moving towards the neck and away from the chest deflection sensor. However, the experiment described above demonstrated that it would be possible to measure deflection at the site of the belt (after it has moved). The additional sensor would also help to reduce the influence of head-to-chest contact on the deflection measurement.

2.3

The protection of children by vehicle safety features

Changes in front seat safety systems are continuously improving the protection afforded to front seat adult occupants. Recent changes, over the last decade or two, include the fitment of airbags (for front and side impact), and seat belt pretensioners and load TRL

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limiters. The implementation of such injury mitigation technologies in the front seats has meant that, together with constraints on seat belt anchorage positions, the front and rear seats of modern cars may have different injury risks for occupants in crashes (Beck et al., 2013). This may even have switched the relative injury risks so that where once the rear seating positions were safer than the front, the reverse is now true (Jakobsson et al. (2011). The use of child restraint systems in cars is not restricted to either the front or the rear passenger positions. As such, child restraints must provide protection in seating positions where airbags, pretensioners and load limiters can deploy, as well as positions where these safety features are not present. As a confounding issue, the use of passenger seats is not limited to either adults or children, but can change from journey to journey. Therefore, passenger seats must accommodate rear-facing integral, forward-facing integral, as well as non-integral child restraints, and the full range of adult occupants. Unfortunately, these users may well have conflicting demands for the seat. Hu et al. (2013) comment that, “The optimal belt anchorage locations and the seat cushion length for older children, adults, and rearfacing child restraint-seated infants conflict with each other”. This implies that compromise is necessary to provide a seat suitable for all types of occupant, but that the resulting arrangement may be sub-optimal for each. At present, advanced restraint system technologies are not incorporated in child restraint safety assessments. There is no formal requirement for a child restraint manufacturer to check how their products may interact with pretensioners, load-limiters and side airbag systems. As these vehicle safety systems promulgate through to the rear seat positions, it may be that a greater emphasis is needed on assessing their interaction with child restraints (to prevent unintended consequences for children). The following two subsections describe the vehicle assessment incentives that may stimulate the adoption of advanced safety systems in the rear seat positions as well as the existing knowledge regarding interactions with child restraints. 2.3.1

Review of regulatory and consumer test procedures for vehicle safety

The safety features in a vehicle are likely to be influenced greatly by the legislative and consumer testing requirements that it is designed to meet. This subsection reviews the main legislative and consumer testing requirements to highlight what “protective guarantees‟ they provide for front and rear seat occupants, in terms of the type of safety features that might be expected to be fitted. It focusses on regions under the 1958 Agreement, but also includes requirements from further afield if they have the potential to influence car features globally. Frontal impact The rear seats are unoccupied in the frontal impact deformable barrier test of UN Regulation 94. This is the same in European Commission Directive 96/79/EC. It is also the same in the various regulatory test procedures currently in place throughout the world. As such, there is no regulatory stimulus to meet a certain provision of safety in the rear seats in front impact crashes. For front seat occupants, the use of a pretensioning and load-limiting seat belt, balanced with an airbag, is routinely shown to be effective in providing increased safety levels over a standard belt restraint system or belt and bag system alone (e.g. Carroll, 2009). This is particularly evident for occupants of similar size to the mid-sized male crash test dummy (Carroll et al., 2010).

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UN Regulation 16 specifies that all seating positions in an M1 3 vehicle are fitted with three-point seat belts having an emergency locking retractor. Furthermore, it prescribes a dynamic sled test with the seat belt system at 50 km/h with a peak acceleration of between 26 and 32 g, during which the dummy must have a pelvis forward displacement of between 80 and 200 mm and a thoracic forward displacement of between 100 and 300 mm. This may constrain the range of forces that can be used in seat belt load-limiting systems, unless adaptive or progressive technologies are adopted. These limits can be exceeded for front outboard seats also protected by an airbag and are reduced by half for cases of a seat belt with a pre-loading device. In contrast with the legislative test, the rear seats are occupied in the main European consumer test for vehicle occupant protection. The EuroNCAP front impact test is performed with 18 month old and three year old dummies, placed in child restraints ‘recommended’ by the car manufacturer (see www.euroncap.com). The Q-Series dummies replaced the P-Series in the test protocols from 2013, but the dynamic assessment remains focussed on the head, neck and chest. From 2015, Euro NCAP will use six year old (Q6) and ten year old (Q10) dummies in non-integral child restraints. Side impact The struck-side (driver’s) front seat is occupied with an ES-2 dummy in the side impact mobile deformable barrier test of UN Regulation 95; however, the rear seat is unoccupied. This is the same in European Commission Directive 96/27/EC; therefore in Europe, there is no regulatory assessment of safety provisions for rear seat occupants in a side impact. There is no incentive, therefore, for vehicle manufacturers to fit more advanced protection systems, such as side airbags, in rear seating positions. In fact, vehicles can pass the regulatory test without side airbags in the front seats, although other features might be needed. For vehicles sold into the US market, the requirements set out in Federal Motor Vehicle Safety Standard (FMVSS) 214 must be met. For the barrier test, the struck-side rear seat is occupied with a SID IIs 5th percentile female dummy. The sitting height of this dummy is about 780 mm. It seems to be the intention that vehicles for the US market provide protection in both the front and rear seating positions. Curtain airbags are one means of providing such protection (for the head) and this test encourages manufacturers to extend them down as far as the head height of the SID IIs 5th percentile female dummy. Elsewhere in the world, the use of mid-size male dummies for side impact testing does not put such emphasis on protection for a diverse range of occupants. A UN Global Technical Regulation is being drafted to introduce a ‘worldwide’ pole side impact test. The main benefit likely to arise from such changes to the regulatory assessment of cars will come through the more widespread fitment of head-protecting airbags (Edwards et al., 2010a). As noted above, such airbags are not needed to meet existing European regulatory test requirement. The draft procedure does not include a rear seat occupant, but some manufacturers may fit a curtain airbag that extends across both the front and the rear seating positions. Nevertheless, the efficacy of the curtain

3

Vehicles designed and constructed for the carriage of passengers and comprising no more than eight seats in

addition to the driver’s seat, as defined by Framework Directive 2007/46/EC.

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airbag, if fitted, would not be assessed for rear seat occupants (unless a dummy is installed in the rear). The Euro NCAP side impact assessment specifies a mobile deformable barrier test; and a pole test may also be performed if the car is fitted with head-protecting side airbags. In the barrier test, the outermost rear seats are occupied, with an 18 month old dummy positioned on the struck-side and a three year old dummy on the non-struck-side (see www.euroncap.com). No dummies are placed in the rear seats for the pole test. As noted above, the Q-Series replaced the P-Series in the protocols from 2013 and taller dummies (Q6 and Q10) will be used from 2015. In the current plan, the Q10 will be placed on a booster cushion on the struck-side of the car and hence the car will need to provide side impact protection for this dummy. 2.3.2

Review of literature

The seat belt directive requires that children less than 150 cm in height travel in a child restraint system, although it also allows Member States to specify the use of a child restraint up to 135 cm only. This subsection reviews literature on the interaction between children and vehicle restraint systems. The intention was to support discussions on the point at which a vehicle’s safety features can be expected to contribute to the protection of a child. Frontal impact A Hybrid III six year old dummy was used by Bohman et al. (2006) in frontal sled tests simulating the rear seat of a car to investigate the effect of a pretensioner or pretensioner and load limiter on the performance of various boosters in frontal impact tests. Their results showed that adding a pretensioner and a load limiter to a standard retractor reduced loading of the head, neck and chest for all tested booster cushions. After this work, Jakobsson et al. (2007) also commented that the introduction of load limiters to the rear seat positions, in conjunction with integrated boosters, enabled the possibility to enhance crash test performance for child dummies. This has subsequently been endorsed by Schnottale et al. (2011) after body-in-white sled testing with load limiter and pretensioner belt systems on a sled with the Q6 on a variety of booster seats. Also, Croatto and Masuda (2013) reported that a pretensioner and load limiter reduced the head acceleration, chest deflection and abdomen pressure for the Q10 in a booster seat during sled tests. However, the exact interaction between pretensioners and forward-facing boosters may need to be monitored. Tylko and Bussières (2012) have already noted potential issues with poor belt-routing for a Hybrid III ten year old dummy on a booster cushion in a rear seat with pretensioner during a full-scale impact test. Croatto and Masuda (2013) also identified that the Q10 chest deflection was higher in a test with pretensioner and force-limiting seat belt, but no child restraint. This was thought to be because of a smaller shoulder belt migration towards the neck with the advanced belt system, so that the belt stayed closer to the deflection measurement points. No information was available from the literature regarding how pretensioners and load limiters interact with rear-facing child restraint systems; however, this may be of limited importance in the future with greater use of ISOFIX (as envisaged with the implementation of UN Regulation 129). It is also not certain to what extent vehicle manufacturers may need to use pretensioners and load limiter technologies in the rear

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seat positions. Typically, a good Euro NCAP child safety rating can be achieved without such investment. In which case, it is down to the corporate safety beliefs of each particular manufacturer as to whether or not they are included for a model. This may change after the use of taller dummies, which is planned from 2015 (as noted in Subsection 2.3.1). The ten most popular vehicles in European sales were reviewed (based on sales for the year-to-date up to July 2013 (JATO, 2013) to determine if rear seat pretensioners were used and, where available, to note the corresponding child safety score from Euro NCAP. The information regarding whether or not a pretensioner was fitted was taken from the rescue cards for each vehicle. The Euro NCAP scores included, where available, both the total score and the points awarded on the basis of the dynamic tests (maximum of 24). These details are reproduced in Table 4. As is clear from this table, none of the bestselling vehicles in Europe use a pretensioner system in the rear seats. However, in most cases, the Euro NCAP child safety scores are very good, if not perfect. Table 4: Use of pretensioner technology in the rear seats and Euro NCAP scores for top-selling European models Manufacturer

Model

European sales

Pretensioner fitted

Euro NCAP child safety rating (total)

Euro NCAP score (child safety dynamic performance combined)

Volkswagen

Golf

274,984

No

89%

22.6 points

Volkswagen

Polo

166,435

No

86%

24 points

Ford

Fiesta

176,364

No

86%

23 points

Renault

Clio

176,168

No

89%

23.5 points

Ford

Focus

141,794

No

82%

24 points

Peugeot

208

155,724

No

78%

21.5 points

Opel/Vauxhall

Astra

122,425

No

84%

23.1 points

Nissan

Qashqai

131,414

No

40 points

-

Opel/Vauxhall

Corsa

148,908

No

32 points

-

BMW

3-Series

120,267

No

84%

23.9 points

Side impact With a 5th percentile occupant, thorax side airbags have been shown to reduce, substantially, dummy rib deflections in full-scale tests and hence the risk of receiving an AIS≥3 thoracic injury (Bohman et al., 2009). Due to their smaller stature and lower sitting height, children have the potential to sustain serious head injuries from contact with the vehicle interior even in minor crashes (Bohman et al., 2009). However, Andersson et al. (2012) showed through finite element numerical simulation that head airbags can be effective for children. They performed IIHS and US NCAP side impact test simulations using the three-year-old THUMS human body model on a backless beltpositioning booster and a SID IIs dummy model, said to represent a 50 th percentile 12 year old. Of the car parameters they investigated (vehicle mass, side impact structure stiffness, a head airbag, a thorax-pelvis airbag and a seat belt with pretensioner), the head airbag was the most effective in mitigating injury risk. Its use TRL

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led to the reduction of linear head acceleration peak values by 54 g for the three year old and 78 g for the SID IIs. The pretensioning seat belt showed similar reductions in peak linear head acceleration values for the two occupants. Table 5 shows the fitment of side airbags in the rear seating positions of the top-selling cars in Europe, along with the Euro NCAP comment on protection of the child dummies (in the side impact test). With the focus on smaller dummies, protection is provided primarily by the child restraint system, although this does not appear to be hindered by curtain airbags. With the move to taller dummies expected for 2015, including the use of the Q10 on a booster cushion, curtain airbags may need to contribute to the protection of the head (for occupants of this size). Far-side occupants are at a substantial risk of severe injury and death in crashes (Mathews et al., 2013). As a potential countermeasure, those authors found that electromechanical motorised seat belt retractor (EMSR) activation significantly reduced head and spine kinematics for both paediatric and young adult subjects in low-speed volunteer sled tests. Presumably, the use of a booster seat instead of a cushion would also be effective in the far-side impact configuration. Both a pretensioning seat belt and a child restraint with side wings have the objective of reducing excursion (providing containment) in side impacts, thereby reducing the risk of potentially injurious contacts with intruding structures, other vehicle components or other vehicle occupants. 2.3.3

Summary

In front seats, the adoption of pretensioning, load-limiting seat belts and head-protecting side airbags will only increase as these systems are taken up in the vehicle fleet, are rewarded by consumer information test programmes and are shown to be effective in the real world. Therefore, there is a need to understand how child restraints interact with these modern restraint systems to ensure the best levels of protection into the future. Initial observations suggest that pretensioners and side airbags should be of great benefit for child occupants as well as adults. However, some authors have alluded to the fact that the expected benefit may not always be observed or correctly assessed in impact tests. In rear seats, the stimulus for adoption of advanced seat belt systems is less obvious. Some manufacturers believe that the incorporation of such systems is worthwhile, whilst the majority of those responsible for the top selling vehicles in Europe don’t, yet. Therefore in frontal impacts there is also a need to continue evaluating child restraints with a view to seating positions without a pretensioner or load limiter. For side impact protection, pole side impact tests will ensure that airbags are fitted to protect the head of adult front seat occupants. However, there is no formal requirement, in place now or in preparation, as to why curtain airbags should extend to protect rear seat occupants in Europe. Despite this, the top-selling vehicles in Europe do mostly make use of full length curtain airbags. The next issue then becomes whether they deploy low enough to protect the 5th percentile female or perhaps even lower to offer protection for children in child restraints. This protection cannot be relied upon given the requirements of the side impact testing of vehicles at the moment. Where a vehicle is providing side impact protection expecting the use of an integral booster it should be ensured that this does not adversely interfere with a booster seat or rear-facing child restraint.

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Table 5: Use of side airbag technology in the rear seats and Euro NCAP scores for top-selling European models Manufacturer

Model

European sales

Side airbag fitted

Euro NCAP comment

Volkswagen

Golf

274,984

Curtain

In the side impact, both dummies were properly contained by the protective shells of their restraints, minimising the likelihood of head contact with parts of the car interior.

Volkswagen

Polo

166,435

Curtain

Based on dummy readings in the frontal and side impact tests, the car scored maximum points for protection of both children.

Ford

Fiesta

176,364

Curtain

In the side impact, both dummies were properly contained by the protective shells of their restraints, minimising the likelihood of head contact with parts of the car interior.

Renault

Clio

176,168

None for rear seat occupants

The Clio scored maximum points for the protection provided to the 18 month dummy in the dynamic impact tests.

Ford

Focus

141,794

Curtain

The Focus scored the maximum points available for the protection of the 3 year child in the frontal and side impact tests, and lost only a fraction of a point for the 18 month infant.

Peugeot

208

155,724

Curtain

In the side impact, both dummies were properly contained by the protective shells of their restraints, minimising the likelihood of contact with parts of the car's interior.

Opel/Vauxhall

Astra

122,425

Curtain

In the side barrier test, both dummies were properly contained by their restraints.

Nissan

Qashqai

131,414

Curtain

The car scored maximum points based on the measurements recorded by the two child dummies in the front and side tests.

Opel/Vauxhall

Corsa

148,908

Curtain

-

BMW

3-Series

120,267

Curtain

In the side impact, both dummies were properly contained by the protective shells of their restraints, minimising the likelihood of contact with parts of the car's interior.

2.4


Injuries to children in non-integral child restraint systems tend to occur in the head, chest and abdomen (in both front and side impact collisions). It seems likely that improving the protection afforded to these body regions would be beneficial. However, there are too few children in representative databases to identify priorities with any TRL

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statistical confidence or to quantify benefits of potential interventions in a meaningful way. Expanding the provision of such data would enable a more targeted approach to be taken to regulatory changes in the future. With no such evidence, pragmatic decisions must be made that stakeholders can agree upon. For example, most stakeholders would agree that UN Regulation 129 should maintain the assessment of non-integral child restraint systems in the head, chest and abdomen (in front impact at least). The Q-Series dummies offer more measurement options than the P-Series in these body regions (and others), such as chest deflection and abdominal pressure. It seems sensible to adopt these new measurement options, particularly where they offer advantages over the traditional measurement made with the P-Series dummies in UN Regulation 44. Potential parameters and thresholds for the Q-Series are discussed in Chapter 4. Simply adopting the test procedure from UN Regulation 44 and replacing the P-Series with the Q-Series (albeit with a new test bench) may not deliver significant improvements in the performance of non-integral child restraint systems; it may even have a detrimental effect. Our experiments showed that the enhanced measurement options and component-level biofidelity of the Q-Series is undermined by its interaction with the three-point seat belt. Although the interaction between the dummy and the lap part of the belt can be improved (by accessories to prevent belt intrusion and by set-up positioning), the test procedure may not encourage features that keep the belt low on the pelvis. Similarly, movement of the diagonal part of the belt towards the neck reduces the contribution made by the child restraint in keeping the occupant within the belt. It also reduces the value of the chest deflection sensor (in its present position).

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3


3.1

Overview

The front impact test conditions in UN Regulation 129 are the same as those in UN Regulation 44. They specify an impact speed of 50 km/h with a deceleration (or acceleration) corridor that peaks at 20 – 28 g. Information about the source of these conditions is difficult to find, but TRL understands that they were derived from full-scale front impact experiments using cars that were representative at the time (i.e. the late 1970s/early 1980s). These historic experiments were carried out against a rigid barrier that extended across the entire width of the car. This type of test arrangement typically results in high passenger compartment deceleration (because there is limited deformation of the frontal structure). It serves as an ideal reference, therefore, for testing restraint systems in a worst-case condition (for any given impact speed). Vehicle crashworthiness has progressed since UN Regulation 44 was introduced: firstly, with the introduction of the front impact test procedure in UN Regulation 94, and then with the introduction of a higher severity front impact test by the European New Car Assessment Programme (Euro NCAP). The UN Informal Group on child restraint systems decided to adopt the UN Regulation 44 test conditions (for the new Regulation) after reviewing crash pulses from a selection of UN Regulation 94 and Euro NCAP tests (Hynd et al, 2010). They compared the crash pulse from various full-scale front impact tests against the test conditions in UN Regulation 44 (and proposed for UN Regulation 129). These full-scale tests were typically undertaken for other purposes, but showed that: i.

A typical Euro NCAP pulse would subject a child restraint system to an impact that is longer in duration, and with a higher overall severity, than UN Regulation 44;

ii.

A typical UN Regulation 94 pulse has a less severe initial deceleration compared with the UN Regulation 44 test conditions, although the peaks are similar in magnitude and the overall duration is similar;

iii.

A typical pulse using the progressive deformable barrier displays a similar severity to the UN Regulation 44 conditions, although this is based on a limited number of vehicles and the pulse varied depending on vehicle size.

Based on this evidence, the Informal Group concluded that the current UN Regulation 44 test conditions were appropriate for UN Regulation 129. However, these data were derived from impact tests with an offset deformable barrier that extends across 40 per cent of the car’s width. This arrangement is a stringent test of a vehicle’s structure, but is likely to result in lower passenger compartment deceleration than a full-width collision. The new UN Regulation presents an opportunity to improve the protection of children in collisions by encouraging the design of enhanced child restraint systems. The performance of child restraints in front impact collisions is currently very good, provided they are used correctly. Even so, in the context of delivering enhanced child restraints, it would seem appropriate to examine what further improvements might be made. This chapter summarises research undertaken in this project to examine whether the front impact pulse should be updated to reflect modern vehicles and the type of collisions that children are involved in. It describes collision data analyses as well as

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impact experiments to compare a typical vehicle crash pulse with the sled test conditions in UN Regulation 129.

3.2

The characteristics of frontal impact collisions involving children

This section investigates the characteristics of front impact collisions involving children. It is intended to support the evidence-base for decisions about the type of crash pulse that should be used to assess the performance of child restraint systems in UN Regulation 129. It begins with a brief overview of some significant European studies on front impact before describing a new analysis of front impact collisions involving children. 3.2.1


Characteristics of front impact collisions Richards et al. (2010) carried out a comprehensive study on front impact collisions for the European Commission to help prioritise potential changes to vehicle legislation. This included analyses of in-depth and representative databases from Great Britain and Germany. Although this study focussed on adults, it can be used as a basis to understand the characteristics of typical front impact collisions. However, it would be necessary to assume that children are involved in broadly the same kinds of collisions as adults, if the findings were to be considered for UN Regulation 129. Figure 16 shows the vehicle overlap for cars in car-to-car (including LGV) impacts in Great Britain, as a percentage of the injury group of the driver of that car. This shows that a large proportion of front impact collisions have a large overlap (>90%). The Figure also provides similar data from Germany and also finds a large proportion of impacts have a large overlap (>90%). Full-width test conditions may be more appropriate for testing restraint systems. These figures show that they are also more representative of the majority of front impact collisions (for adults at least).

Germany

Great Britain

Figure 16: Vehicle overlap as a percentage of injury group for drivers in car-tocar/LGV impacts (source: Richards et al. 2010) Figure 17 shows the longitudinal loading and provides another means of investigating the nature of front impact collisions. It is useful as an additional measure (to overlap) because it confirms that the significant load-bearing structures were engaged on both sides of the vehicle. Richards et al. (2010) provided data for Great Britain only;

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nevertheless, Figure 17 shows that a large proportion of vehicles displayed loading to both longitudinal members, which was consistent with the findings from Figure 16.

Figure 17: Longitudinal loading as a percentage of injury group for drivers in car-to-car/LGV impacts in Great Britain (source: Richards et al. 2010) Injuries to children in front impact collisions Data presented at the Informal Group seems to indicate that most collisions involving children are covered by the 50 km/h impact test currently specified in UN Regulation 44 (notwithstanding the possible need to fine-tune the deceleration corridor to be more representative of modern vehicles). For example, Figure 18, obtained from Lesire and Johannsen (2011), shows the velocity change of collisions involving children, in injury groups, from the German In-Depth Accident Study (GIDAS). The data were derived from collisions that took place between 1999 and 2008. This found few children were injured in the highest severity group (MAIS3+), although it may also have been interesting to look at injuries at MAIS2 (and above) too. MAIS2 injuries can include fractures and other internal injuries, and hence it would be desirable to mitigate these injuries, particularly for children.

Figure 18: Number of children in injury severity groups in a German sample against velocity change (km/h) (source: Lesire and Johannsen, 2011) The CASPER project database includes 2644 children that were seated in a child restraint system in a front impact collision (Kirk, 2012). Of these, 117 children received an

4

This includes cases from the CHILD project, but excludes cases from CREST.

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MAIS≥2 injury. Whilst this database is not representative, it illustrates that children in child restraints are injured at these higher injury severities (and crash severities, since a front impact velocity change must have exceeded 40 km/h to be considered for the project). 3.2.2


Section 2 in Annex 1 describes a new analysis of representative databases from Great Britain and Germany, undertaken to establish the characteristics of front impact collisions involving children. The approach was similar to that of Richards et al. (2010) to facilitate comparisons with their analysis of drivers (for which larger samples were available). Although the sample sizes were small for children, most collisions occurred at speeds below 50 km/h with a direction of force between 11 and 1 o’clock (over half were at 12 o’clock in both the British and the German samples). This suggests that the impact speed and configuration of the front impact test in UN Regulation 129 are consistent with the type of collisions that children are involved in. Figure 19 shows the longitudinal loading as a percentage of the injury group for children in front impact collisions. Collisions with loading to both longitudinal members (‘fullwidth’ collisions) were a significant proportion, and seemed to be over-represented for the more seriously injured children. This suggests that it would be appropriate for the sled deceleration pulse in UN Regulation 129 to be representative of full-width collisions (rather than offset collisions).

Great Britain

Germany

Figure 19: Longitudinal loading as a percentage of injury group for children in front impact collisions Some of the variables described above were used to group children into collisions that were either ‘Covered by UN Regulation 129’ or were ‘More severe than UN Regulation 129’. This is shown in Figure 20. Collisions were more severe than the regulatory test if the impact speed was greater than 50 km/h and the overlap was greater than 10 per cent (to exclude side-swipes and very low overlap crashes). Although this approach was unable to consider the shape and magnitude of the real crash pulse, it does help to quantify target populations, albeit at a high level. Figure 20 shows that most children were involved in a collision that was covered by the front impact test conditions in UN Regulation 129. This included children with no or minor injuries (MAIS≤1) as well as children with more severe injuries (MAIS≥2).

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Great Britain

Germany

Figure 20: Proportion of children in collisions covered by the regulatory test (Note that the comparison could not be made for over 20 per cent of children in the British data because the velocity change was unknown) The absolute numbers were very low and cannot be used to draw conclusions with any level of statistical confidence; nevertheless, Figure 20 shows that injured children (at MAIS≥2) were over-represented in the group of children in more severe collisions (than the regulatory test). The analysis did not take account of restraint type, primarily to maximise the sample sizes, but also because (surprisingly) restraint type did not influence the injury severity distribution greatly (See Annex 1, Section C.3). Closer examination of the children in child restraints (on a case-by-case basis) revealed that: i.

Testing child restraint systems at a higher severity (60-70 km/h) might be beneficial for some injury mechanisms; however,

ii.

Better restraint of older children by the three-point seat belt (even when combined with a non-integral child restraint), would be a more effective countermeasure for some injury mechanisms.

3.3

Comparison of vehicle and sled pulse characteristics and their effects

Annex 4 describes a car-to-car front impact experiment carried out with child dummies seated in child restraint systems in the rear seat (of each car). It also describes a series of sled experiments, with the same child restraints, performed to the front impact pulse in UN Regulation 129 (and Regulation 44) and to an alternative pulse proposed by Hynd et al. (2010). This alternative pulse was derived from full-width crash tests carried out by the National Highway and Traffic Safety Administration (NHTSA) in the United States. 3.3.1

Pulse comparison

Figure 21 shows the passenger compartment deceleration from each car in the full-scale experiment overlaid with two different front impact pulse corridors. The chart on the left shows the car data with the corridor specified in UN Regulation 129 (and Regulation 44). The chart on the right shows the corridor proposed by Hynd et al. The cars used in the experiment (two identical Alfa Romeo MiTo superminis) were stiffer than the cars used to derive the corridor in UN Regulation 129. This corridor did not reflect the characteristics of this modern car in a 50 km/h front impact that extended across its entire width. The cars were similar in stiffness to the pulse corridor proposed by Hynd et al. This corridor

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was more representative of the stiffness characteristics of the cars than the pulse specified in UN Regulation 129.

UN Regulation 129 pulse

Pulse proposed by Hynd et al. (2010)

Figure 21: Passenger compartment deceleration in the car-to-car experiments compared with front impact sled pulses 3.3.2

Effect of pulse differences on dummy loading

Figure 22 compares dummy measurements between the car-to-car and the sled experiments. The chart on the left shows head acceleration and the chart on right shows chest acceleration. The front impact pulse corridor proposed by Hynd et al. resulted in head and chest acceleration levels that were very similar to those in the car-to-car experiment. The front impact pulse in UN Regulation 129 underestimated the head and chest acceleration in the car-to-car experiment. In some cases, the UN Regulation 129 performance limit was exceeded in the car, and in the experiment with the Hynd pulse, but not in the experiment with the UN Regulation 129 pulse.

Head acceleration (3 ms value)

Chest acceleration (3 ms value)

Figure 22: Q3 and Q6 dummy measurements in different child restraints and impact conditions

3.4


The front impact test speed in UN Regulation 129 seems to be set at an appropriate level for the majority of collisions that children are involved in. TRL understands that the sled deceleration corridor (specified alongside the test speed) was derived from full-width car-to-barrier experiments carried out before it was introduced in UN Regulation 44 (in the late 1970s/early 1980s). A full-width collision represents a worst-case for testing TRL

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restraint systems because the passenger compartment deceleration is likely to be higher than that in in offset collision (for any given impact speed). Our in-depth samples from Great Britain and Germany suggest that a significant proportion of front impact collisions involving children are likely to be full-width collisions (with MAIS≥2 injuries overrepresented in this group, compared with off-set and low overlap collisions). Defining a sled deceleration corridor in UN Regulation 129 that reflects the deceleration pulse of a car in a full-width collision (rather than an offset collision) would be appropriate; not only to test child restraints under worst-case conditions, but also in a common collision scenario (particularly for injured children). However, our experiments found that the current corridor underestimated the passenger compartment deceleration in a full-width car-to-car experiment with a typical supermini. The corridor also underestimated the dummy head and chest acceleration such that the regulatory performance limits were exceeded in the car, but not in the regulatory test. Updating the regulatory deceleration corridor would ensure that it remains relevant for modern cars (in full-width collisions). Hynd et al. (2010) proposed a corridor that seems to be a reasonable candidate for a new regulatory corridor (for use with the same impact speed). The new corridor would increase the severity of the front impact test marginally; however, our experiments suggest that it would better reflect the characteristics of modern cars and reproduce the dummy loading more accurately than the current corridor. It should be possible to adjust the corridor in this way without influencing (adversely) the protection of children in less severe collisions. For example, specifying a chest deflection limit would help to prevent restraints from becoming too stiff at lower severities. A relatively small proportion of front impact collisions occur above the impact speed in UN Regulation 129. Given that children do not seem to be exposed to such high-severity collisions in any significant numbers, there may be limited justification for a step change in the severity of the front impact test conditions (notwithstanding the adjustment in severity described above).Nevertheless, our representative samples from Great Britain and Germany included a small number of cases in which it was feasible to mitigate the child’s injuries with a better restraint system (on the basis that there was no significant structural failure and intrusion of the passenger compartment). There were limited representative collision data with which to quantify statistically how well the front impact test conditions reflect the characteristics of modern cars and the type of collisions that children are involved in. Reasonable observations were made that took account of experimental results as well as collision data. However, improving the provision of representative data for children would allow robust assessments to be made of the benefits of regulatory changes. Ideally, such data would span the European Union, but at present, very few Member States routinely collect information with sufficient depth and breadth.

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4


UN Regulation 129 introduces the Q-Series dummies into legislation. With the introduction of a new dummy (or series of dummies), it is usually necessary to derive injury risk curves that relate the dummy’s measurements to the risk of injury in humans (for a given level of severity, such as AIS≥3). Thresholds for the dummy’s measurements can be drawn from such risk curves and applied in test procedures for cars and/or safety subsystems. These risk curves (and subsequent thresholds) must be appropriate for the particular age and size of occupant that the dummy represents, and for the particular application of the dummy (Mertz, 2002). If they fulfil these criteria (and any assumptions made are reasonable and appropriate), they can provide an evidence-based means of assessing the protection afforded to vehicle occupants. They can also be used to target particular body regions and/or injury mechanisms that are deemed to be a priority. UN Regulation 129 specifies performance thresholds for head and chest acceleration in the front and rear impact tests and head acceleration and HIC in the side impact test. It also specifies requirements for head excursion in front and rear impact and head containment in side impact. The regulation is similar to UN Regulation 44 in that it focuses primarily on the assessment of head and chest protection (for front impact). The injury assessment criteria and performance limits took account of those published by EEVC Working Groups 12 and 18 (see Wismans et al., 2008) whilst balancing the needs of a regulation. Other inputs have been provided from research projects such as CASPER and EPOCh, both in terms of the body regions that should be specified and what the thresholds should be. This chapter summarises research undertaken in this project to investigate which body regions need to be protected for children and hence where the performance evaluation of child restraint systems in UN Regulation 129 should be targeted. It also reviews the latest proposals for injury criteria and performance thresholds for the Q-Series dummies, identifying any gaps and their implications for the regulation.

4.1 4.1.1

Injuries to children and priorities for protection Review of European studies

Table 1 and Table 2 in Section 2 identified injuries that should be a priority for prevention for children in non-integral child restraint systems. Injuries to children in non-integral child restraints tend to occur in the head, abdomen and the extremities. The EEVC Working Group 12 and 18 review of accident data made the following recommendations for front impact collisions (Wismans et al., 2008): i.

For infants and toddlers (Group 0/1), the whole priority should lie on protecting the head and neck from injury;

ii.

This priority shifts to the head, chest and abdomen as children grow up and start to become taller (Group 2/3/adult belt).

It is important that new dummies and performance or injury criteria reflect these injuries, as have been observed in the field. Consequently, Working Groups 12 and 18 recommended injury assessments for the head, neck, chest and abdomen areas.

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4.1.2


Section 3 in Annex 1 describes an analysis of representative, in-depth collision databases from Great Britain and Germany. The analysis was undertaken to investigate which body regions need to be protected in front and side impacts and hence where the regulatory performance evaluation should be targeted. There were very few injuries to children at AIS≥2 in the representative samples from Great Britain and Germany. This is illustrated in Figure 23 and Figure 24, which show the distribution of AIS≥2 injuries by body region for each restraint type in front and side impact collisions respectively. Clearly, very limited representative and in-depth realworld data is available for children in Europe. However, it cannot be concluded that these injuries do not take place in sufficient numbers to warrant intervention. National databases show that significant numbers of children are killed or seriously injured each year on European roads, although a portion of these children are likely to be unrestrained. It was impossible to quantify which body regions need to be protected in a statistically robust way. However, there were clear trends and for targeting the regulatory performance evaluation, it was found for all impact types and restraints that there is good evidence that the focus should be on the protection of the head, chest and abdomen.

Great Britain

Germany

Figure 23: Body region injured by restraint type (AIS≥2) – Front impact

Great Britain

Germany

Figure 24: Body region injured by restraint type (AIS≥2) – Side impact

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4.2


Annex 7 describes a review of published injury criteria and performance thresholds for the Q-Series dummies (for front and side impact). It compares the injury criteria and thresholds from three key sources and highlights any differences (taking into account any differences in the methods employed by the different groups). It also highlights gaps that need to be closed to fulfil the aims of the regulation (to deliver “enhanced child restraint systems”). The main aim, in performing this analysis, was to support the evidence-base for the dummy injury assessment criteria and performance limits specified in UN Regulation 129. The three sources (of injury risk curves and thresholds) available for the analysis were: i.

EEVC Working Groups 12 and 18 derived injury risk functions for the Q-Series dummies from accident reconstruction experiments, supplemented with scaling (see Wismans et al., 2008). The accident reconstruction data came from a European Framework Programme project: CHILD (CHild Injury Led Design, 20022006).

ii.

CASPER (Child Advanced Safety Project for European Roads), carried out further accident reconstructions to support the development of injury criteria and performance limits for the Q-Series (see Johannsen et al. 2012b).

iii.

EPOCh (Enabling Protection for Older Children) developed the Q10 dummy and proposed injury criteria based on scaling adult injury risk functions (see Hynd et al. 2011).

4.2.1

Analysis of available criteria and limits

Front impact Table 6 compares the thresholds specified in UN Regulation 129 with those proposed by EEVC Working Groups 12 and 18 and the CASPER project for the Q0, Q1 and Q1.5 dummies5. Table 7 makes a similar comparison for the Q3, Q6 and Q10 dummies. A reasonable set of evidence-based thresholds are available with which to assess the performance of child restraint systems in front impact test procedures. At present, UN Regulation 129 specifies thresholds for head acceleration and chest acceleration only, but thresholds are available for other body regions and/or measurement parameters. The application of regulatory limits and availability of other thresholds is summarised below for each of the key body regions: Head - The regulatory limits specified in UN Regulation 129 are broadly consistent with the thresholds proposed in the literature (from the three sources identified above); however, by keeping the limits the same (for the Q0, Q1 and Q1.5 and for the Q3, Q6 and Q10), they correspond to a slightly different risk of AIS≥3 injury, for each occupant size. Neck – No limits are specified in the regulation, although the upper neck tensile force (+Fz) and flexion bending moment (+My) must be measured for monitoring

5

EEVC derived two sets of thresholds at AIS≥3 level: one using the certainty method, and one using logistic

regression. Only those derived using logistic regression are shown here, but the full suite of thresholds is shown in Annex 7.

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purposes. This monitoring will be essential to ensure that loads are not transferred to the neck, to minimise other parameters that are regulated. Chest – UN Regulation 129 specifies a pragmatic limit for chest acceleration, based on that specified in UN Regulation 44. Although evidence for such a limit was not found from the sources reviewed here, it seems likely that it will maintain the current good performance of child restraints in this region (at least for harness-based systems). A limit for chest deflection would offer the additional benefit of detecting concentrated loading through improper restraint. However, the thresholds proposed for chest deflection appear to be based on the risk of rib fracture only, and do not account fully for injuries to the organs and soft tissues. Although a chest injury threshold that takes significant account of rib fracture may be appropriate for adults, serious chest injury can occur in children without rib fracture. Abdomen – No abdomen performance requirements are specified in UN Regulation 129 (i.e. in Phase 1, for integral child restraints). Abdomen pressure thresholds were proposed for the Q3 and the Q6 in the literature, but these need to be extended for the Q1.5 and the Q10. This assumes that the assessment of abdominal protection in UN Regulation 129 will cover all forwardfacing child restraints (i.e. integral and non-integral). Table 6: Q-Series injury criteria and limits from UN Regulation 129, EEVC Working Groups 12 and 18 and the CASPER project - Q0 to Q1.5 Head

Source

Risk of injury

HIC

(15/36)

Neck

A 3 ms (g)

+Fz (N)

Chest +My (Nm)

Dx (mm)

Abdom.

A 3 ms (g)

P (bar)

Q0 dummy UN R129 limits EEVC

600

75

*

*

-

55

-

UN R94 (scaled)

477

79

433

13

-

-

-

AIS≥3 20% LR

523

85

498

17

-

-

-

AIS≥3 50% LR

671

104

546

20

-

-

-

600

75

*

*

-

55

-

UN R94 (scaled)

447

67

951

42

52

-

-

AIS≥3 20% LR

491

72

1,095

53

40

-

-

AIS≥3 50% LR

629

88

1,201

64

59

-

-

AIS≥3 20% SA

-

-

1,000

-

-

-

-

AIS≥3 50% SA

-

-

1,300

-

-

-

-

Proposal

-

-

1,200

-

-

-

-

600

75

*

*

-

55

-

UN R94 (scaled)

526

70

1,080

48

49

-

-

AIS≥3 20% LR

578

76

1,244

61

31

-

-

AIS≥3 50% LR

741

93

1,364

74

56

-

-


CASPER

Q1.5 dummy UN R129 limits EEVC

* For monitoring purposes only LR is logistic regression and SA is survival analysis

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Table 7: Q-Series injury criteria and limits from UN Regulation 129, EEVC Working Groups 12 and 18, the CASPER and EPOCh projects – Q3 to Q10 Head

Source

Risk of injury

HIC

(15/36)

Neck

A 3 ms (g)

+Fz (N)

Chest +My (Nm)

Dx (mm)

Abdom.

A 3 ms (g)

P (bar)


CASPER

800

80

*

*

-

55

-

UN R94 (scaled)

710

75

1,350

63

46.5

-

-

AIS≥3 20% LR

780

81

1,555

79

36

-

-

AIS≥3 50% LR

1,000

99

1,705

95

53

-

-

AIS≥3 20% SA

-

75

-

-

-

-

0.90

AIS≥3 50% SA

-

120

-

-

-

-

1.30

Proposal

-

102

-

-

-

-

1.13

800

80

*

*

-

55

-

986

82

1,824

94

42

-

-

AIS≥3 20% LR

1,083

89

2,101

118

33

-

-

AIS≥3 50% LR

1,389

109

2,304

143

49

-

-

AIS≥3 50% SA

-

-

-

-

-

-

1.09


CASPER

UN R94 (scaled)

Q10 dummy UN R129 limits EPOCh

To be defined during Phase 2

?

-

80

-

-

125

-

56

45

-

* For monitoring purposes only LR is logistic regression and SA is survival analysis

Side impact Very few injury risk curves and measurement thresholds have been proposed for the Q-Series in side impact. This is illustrated in Table 8, which shows the Q-Series thresholds proposed by Johannsen et al. (2012b) from side impact accident reconstructions performed in the CASPER project. UN Regulation 129 specifies limits for head acceleration and HIC in the side impact test procedure (see Table 9). No thresholds are readily-available for other body regions and hence a pragmatic solution would be needed, at least in the short term, if the assessment of child restraints in side impact was extended to other body regions. Table 8: Q3 head injury criteria and performance limits for side impact from UN Regulation 129 and the CASPER project (Johannsen et al., 2012b) Source UN Regulation 129 CASPER

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HIC36

38

800

80

-

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Table 9: UN Regulation 129 head injury performance thresholds for side impact testing of child restraint systems Dummy

Q0

HIC36 Head A 3 ms (g)

4.2.2

Q1

Q1.5

Q3

Q6

600

600

600

800

800

75

75

75

80

80

Proposals for chest deflection thresholds

As occupants get larger, it seems reasonable to assume that the chest deflection threshold for dummies should increase for a given chest injury risk level (to account for the greater chest depth). However, the chest deflection thresholds proposed by Wismans et al. (2008) on behalf of EEVC Working Groups 12 and 18 displayed the opposite trend. They predict that very high chest deflection can be tolerated by younger children for injuries at the AIS≥3 level and that their tolerance reduces as they get larger. This might be plausible for the risk of rib fracture, but it does not seem plausible for organ injuries. These thresholds are shown in Table 10. Table 10: Chest deflection thresholds proposed for the Q-Series by EEVC Working Groups 12 and 18 (Q1 to Q6) and EPOCh (Q10) Q1

Q1.5

Q3

Q6

Q10

20% risk of AIS≥3 injury

40

38

36

33

-

50% risk of AIS≥3 injury

59

56

53

49

56

No other proposals for chest deflection thresholds have been made for the Q-Series. Applying a deflection performance threshold in UN Regulation 129 would ensure that the contribution of compressive loading is accounted for in the assessment of chest injury protection (and that child restraints do not transfer compressive loading to the chest to minimise other parameters that are regulated). An international, collaborative task force is underway with the aim of using accident reconstruction experiments to derive injury risk curves for chest deflection (and abdomen pressure). In the meantime, interim thresholds (using data scaling only) are derived here, that may provide additional insurance for the activities of the task force. Table 11 shows a series of thresholds derived using a scaling formula proposed by Mertz et al. (2003). This formula used geometric scaling only (based on the ratio of chest depth); material properties were not taken into account. Mertz noted that, at the AIS≥3 level, the thresholds were aligned with the risk of rib fractures, whereas at the AIS≥4 level, they were aligned with organ injuries (particularly to the heart). Table 11: Chest deflection limits based on Mertz et al. (2003) belt AIS≥3 and bag AIS≥4 scaling Base level

Q0

Q1

Q1.5

Q3

Q6

Q10

HIII 50th %

50% risk of AIS≥3

18.3

23.7

24.6

26.5

29.3

33.5

50.0

AIS≥4

23.5

30.5

31.6

34.1

37.7

43.1

64.3

Table 12 shows a series of thresholds derived using a scaling formula proposed by Wismans et al. (2008). This formula differed from that used by Wismans to derive the TRL

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thresholds in Table 10 in that it excluded the ratio of bone modulus. However, material properties were considered (by the inclusion of the calcaneal tendon failure stress ratio), which explains why the limits in Table 12 also differ from those in Table 11. Table 12: Chest deflection limits based on Wismans et al. (2008) bag loading scaling Base level 50 % risk of AIS≥3

Q0 11.5

Q1 16.6

Q1.5 18.4

Q3 22.5

Q6 28.2

Q10 32.7

HIII 50th % 50.0

From a pragmatic viewpoint, the two sets of thresholds in Table 11 and Table 12 seem to be more useful than those in Table 10 because: i.

The threshold gets larger as the dummy size increases, which seems to be more plausible for a given risk of chest injury (i.e. all injuries, not just rib fracture);

ii.

All of the dummies are physically capable of measuring deflection up to the threshold.

They are offered here as a potential means of assessing the capacity of child restraints to restrict compressive loading to the chest, notwithstanding the accident reconstruction work of the task force mentioned earlier.

4.3


Phase 1 of UN Regulation 129 seems to capture the most important body regions to protect for children in integral child restraint systems. With regards to front impact, recording the neck forces and moments for monitoring purposes may be sufficient (as an alternative to specifying thresholds), provided that this monitoring takes place and is coordinated between approval authorities. Similarly, it might be reasonable to omit thresholds for chest deflection and abdomen loading in integral child restraints with a harness, because the harness spreads the restraint forces widely over the child’s torso. However, integral child restraints with an impact shield (instead of a harness) can apply more concentrated forces to these body regions (Johannsen et al., 2012a). Such concentrated loading has been implicated in cases of serious injury to children in impact shields (Johannsen at al., 2013). Specifying thresholds for these parameters would ensure a minimum level of performance for integral child restraints regardless of the means of restraining the child in the seating unit. Non-integral child restraints can also apply concentrated loads to the chest and abdomen (via the three-point seat belt). Specifying chest deflection and abdomen pressure thresholds for these child restraints (when they are incorporated in Phase 2 of UN Regulation 129) would be worthwhile; but only if it could be demonstrated that the test procedure (comprising the test bench, the dummies, etc.) was capable of encouraging child restraint designs that optimise the path of the seat belt. Evidence for this was weak in the experiments described in Subsections 2.2.1 and 2.2.2, although improvements were apparent with a second deflection sensor and with changes to the dummy positioning procedure. An assessment of abdominal injury protection is particularly important because the frequency of abdominal injuries seems to increase as children graduate (possibly too soon) from integral child restraints. A rudimentary assessment of abdominal penetration

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by the seat belt is made in UN Regulation 44 and hence introducing (Phase 2 of) UN Regulation 129 with no meaningful assessment of the abdomen might lead to degradation in the performance of non-integral child restraint systems. Chest deflection thresholds for child dummies should ideally take account of the risk of organ injury. The opportunity to specify such thresholds in UN Regulation 129 is dependent on the successful and timely conclusion of the international task force performing accident reconstruction experiments. The scaled thresholds proposed by TRL may provide a back-up to this task force, if needed. Similarly, the opportunity to specify abdominal pressure thresholds is also dependent on the activities of the task force (as well as the full integration of the sensors in the Q-Series package). In these circumstances, it seems appropriate for UN Regulation 129 to wait for this work to be completed, and for discussion and validation of the findings to take place under EEVC Working Group 12. Specifying side impact performance thresholds for the head is likely to target the most severe injuries that children receive. However, serious injuries also occur in other body regions. At present, there are insufficient representative data to comment meaningfully on the distribution of injuries by body region in side impact collisions, but injuries are observed in the chest and abdomen (including the pelvis). Improvements in the protection afforded to these other body regions might be a welcome side-effect of improvements in head protection, but this cannot be guaranteed without measurements and performance thresholds in UN Regulation 129. Very few data are available with which to derive injury-based performance thresholds for other body regions. In the meantime, deriving pragmatic limits based on improving the worst-performing restraints on the market would provide an alternative solution.

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5 5.1

The side impact test procedure Overview

There are no dynamic sled test requirements for the protection of children in child restraint systems in UN Regulation 44. However, traditionally, side impacts are second only to front impacts in causing serious injuries to restrained children in car accidents (Visvikis and Le Claire, 2003). UN Regulation 129 introduces a dynamic side impact test procedure for child restraints in which a representation of the car side is fixed rigidly to the laboratory floor or impact wall. It is arranged such that the ‘door’ passes over and in front of the test bench, impacting the side of the child restraint system. The arrangement of the test equipment is shown in Figure 25. The regulation specifies two main conditions for the test: the relative velocity between the sled and the door panel (essentially the velocity change of the sled as a function of time, peaking between 6.375 and 7.25 m/s at the point of impact); and the maximum intrusion of the panel (100 mm from the vertical midplane of the bench, which equates to 250 mm).

Figure 25: UN Regulation 129 side impact test equipment For a regulatory test, it would be preferable for a procedure to be as simple as possible while resulting in the development of child restraints with enhanced side impact protection that are effective in real car impacts. The side impact test procedure in UN Regulation 129 has been investigated by stakeholders to assess its repeatability, reproducibility and capacity to discriminate between different child restraint systems (Bendjellal, 2013). Nevertheless, it is known that it does not fully and accurately reflect the dynamics of a real side impact collision (Johannsen et al., 2011). This chapter summarises research undertaken in this project to examine how well the side impact test procedure represented the essential loading characteristics of a car-tocar side impact collision. It also examines whether the procedure was capable of distinguishing differences between child restraint systems in terms of the protection they offer in side impacts.

5.2

Vehicle and sled impact conditions and their effects on dummy loading

Annex 5 describes a car-to-car side impact experiment that was carried out with child dummies seated on the struck-side of the target car (i.e. in the front and the rear seat).

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A common B-Segment (supermini) was used in the experiment because previous research indicated that smaller cars may represent a worst-case for the protection of children in struck-side impacts (Cheung and Le Claire, 2006). The results were compared with two sled-based side impact experiments carried out according to the side impact test procedure in UN Regulation 129 (and with the same dummies and child restraints). It was not the intention to perform a detailed assessment of how well the procedure replicated the timings and loadings of real side impact collisions; several full-scale experiments would be needed for such an assessment. Instead, the aim was to provide a general impression of the side impact test and how it compares to a typical collision. 5.2.1

Comparison of pulse and intrusion characteristics

The intrusion velocity of each stuck-side door was calculated by integration of the output from uni-axial accelerometers mounted on the inner door-skin (below the trim). Accelerometers used in this way can be susceptible to local deformation and rotation of the door. Ideally, cross-tubes would have been used, but these could not be fitted without interfering with the child restraint and dummy. Figure 26 shows the intrusion velocity of each struck door in the car-to-car experiment, along with the sled velocity change from the corresponding sled-based experiments. The rear seat data may be unreliable, for the reasons mentioned above, and is included in the Figure for completeness only. The front seat data appeared to be more reliable and were consistent with that reported by Edwards et al. (2010b) in other car-to-car side impact experiments.

Rear seat

Front seat

Figure 26: Intrusion velocity comparison between sled and car-to-car side impact experiments During the period between first contact (of the intrusion surface on the child restraint) and peak head acceleration, the side impact test procedure reproduced the average intrusion velocity and displacement of the front door in the car-to-car experiment. The door travelled 120 cm with an average velocity of 3.1 m/s in the car experiment and 110 cm with an average velocity of 3.4 m/s in the sled experiment. Given that the sled test procedure is a simplification of a side impact collision, it would appear to reproduce the intrusion characteristics over the critical phase of head loading. 5.2.2

Comparison of dummy loading

The side impact test procedure in UN Regulation 129 reproduced the head kinematics observed in the car-to-car side impact experiment reasonably well. This is shown in

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Figure 27 (with the Q1.5 in a rear-facing child restraint) and in Figure 28 (with the Q3 in a forward-facing child restraint). Both child restraints contained the dummy’s head in both experiments; however, Figure 28 also shows that the head of the Q3 dummy was slightly more exposed (but ultimately contained) in the car-to-car experiment than in the sled experiment. This seemed to be caused by the intrusion profile of the struck car, which resulted in the child restraint tilting slightly towards the intruding door.

Car-to-car side impact experiment (rear seat)

UN Regulation 129 side impact test procedure

Figure 27: Q1.5 dummy head containment in rear-facing ISOFIX child restraint

Car-to-car side impact experiment (front seat)

UN Regulation 129 side impact procedure

Figure 28: Q3 dummy head containment in forward-facing ISOFIX child restraint UN Regulation 129 specifies measurement limits for head acceleration and HIC only (for the side impact test). The test procedure reproduced the dummy measurements from the car-to-car side impact experiment very closely for these parameters. This is illustrated in Figure 29. The Figure also shows that the procedure was less capable of reproducing the dummy loads in other body regions. Most notably, the balance between the acceleration and deflection loading in the chest was different between the car-to-car and the sled experiments.

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Q1.5 dummy in rear-facing ISOFIX child restraint

Q3 dummy in forward-facing ISOFIX child restraint

Figure 29: Dummy measurements in the car-to-car and sled-based side impact experiments The side impact test procedure is a very simplified representation of a real side impact collision that was optimised to reproduce the intrusion conditions at the time of maximum head loading (Johannsen et al., 2011). While the side impact test procedure was capable of reproducing the head kinematics and loads from a representative side impact collision (between two identical cars), it was less capable of reproducing realistic loading to the dummy in other body regions. At present, UN Regulation 129 does not specify performance requirements for other body regions.

5.3

Sensitivity of the side impact test procedure to child restraint differences

Annex 6 describes a programme of experiments to investigate whether the side impact test procedure was capable of distinguishing between child restraints with different levels of side impact protection. Specially-adapted child restraints were used, each with very different side impact features and characteristics. It was assumed that these features led to genuine differences in the level of protection afforded by the child restraints. A further experiment with a small extension to the door structure (not specified in UN Regulation 129) was included to investigate its effects on dummy head containment. Its position and size approximated that of a vehicle B-pillar. The head kinematics and interaction with the side wings in the experiments were consistent with changes made to the child restraints. This is shown in Figure 30 (with the Q1.5 in rear-facing child restraints) and in Figure 31 (with the Q3 in forward-facing child restraints). The head remained within the confines of the child restraints when the side wings were reduced, which suggested that head containment was relatively easy to achieve with this procedure.

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Standard child restraint

No foam

Extra foam

Reduced side wings

Figure 30: Q1.5 head containment in rear-facing ISOFIX child restraints

Standard child restraint

No foam

Extra foam

Reduced side wings

No side wings

Reduced side wings – extra ‘B-pillar’

Figure 31: Q3 head containment in forward-facing ISOFIX child restraints The dummy measurements were also consistent with the changes made to the child restraints. This is shown in Figure 32. Although head containment seemed easy to achieve, the rear-facing child restraints met the head acceleration requirement of UN Regulation 129 only when the restraint featured deep side wings and energyabsorbing padding. It seems likely, therefore, that the test procedure would encourage such features to be present in rear-facing child restraint systems that are type-approved to UN Regulation 129. Forward-facing child restraints met the head containment and head acceleration requirements regardless of the depth of the side wings, or the presence of energy absorbing padding. Head containment and acceleration were not influenced greatly by the differences between the (forward-facing) child restraints because the intrusion panel interacted with the child restraint up to the shoulder height of the dummy only. Forwardfacing child restraints with no side wings would be unlikely to pass the test (as shown in Figure 31); nevertheless, the test procedure would not encourage deep side wings (such

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as those that are available now) or energy absorbing foam in child restraints that are approved to UN Regulation 129.

Q3 dummy in forward facing child restraints

Q1.5 dummy in rear-facing child restraints

Figure 32: Dummy measurements in experiments with different child restraint features and characteristics for side impact protection The side impact test procedure was, in general, capable of discriminating between child restraints and their features that were assumed to be important for side impact. The procedure appeared to be a reasonably stringent test of the capacity of rear-facing child restraints to manage head loading. However, there was less evidence that the procedure would encourage features for side impact protection in forward-facing child restraints. In fact, the results demonstrated that it was possible to degrade features that were expected to be of benefit in side impact crashes (such as the depth of side wings and the capacity to absorb energy), while still meeting the requirements of UN Regulation 129. This might lead to degradation in the wider child restraint market, if it becomes apparent that such features are not needed (for UN Regulation 129) and can be removed to reduce manufacturing costs or for other reasons. It should be noted, however, that this finding was based on experiments with a Q3 dummy only; it is possible that the outcome would have been different if the Q1.5 dummy had been used (because its head would be closer to the intrusion panel).

5.4


The side impact test conditions in UN Regulation 129 were set to reproduce the struck door intrusion velocity at around the time of maximum loading to a child’s head. This was reflected in our results, which found that the sled-based regulatory test was capable of replicating the head kinematics and loads from a full-scale side impact experiment (between two identical cars in a perpendicular collision). This suggests that the side impact test provides a reasonable basis for assessing this aspect of child restraint performance. However, the flat profile of the intrusion surface in the regulatory test seemed to favour head containment, whereas the more dynamic nature of real vehicle intrusion seemed harder to manage, particularly for the forward-facing child restraint system (although the dummy’s head was ultimately contained). The side impact test procedure was less capable of replicating the loading to other body regions. This was most apparent in the chest, where the test procedure underestimated chest acceleration, but over-estimated chest deflection (in both forward- and rear-facing child restraints). UN Regulation 129 specifies performance requirements for head

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acceleration and HIC only (for side impact). There are very limited real-world injury data for children in side impact collisions with which to justify extending the assessment to other body regions (See Chapter 4). However, it cannot be concluded that the problem is small in these other body regions until further data becomes available. Our results suggest that if it does become desirable to assess the protection afforded to other body regions, such as the chest, a pragmatic solution might be needed. For instance, chest deflection might be a useful parameter, assuming that it would be preferable to err on the side of stringency (and that an appropriate limit could be agreed). These findings were based on a comparison between the regulatory (sled) test and one car-to-car side impact only. Although the car was representative of the wider supermini market, it is possible that the characteristics of the specific car influenced the results in some way. Similarly, one rear-facing and one forward facing ISOFIX integral child restraint system were used as a basis to make comparisons between the sled test and the car-to-car experiment. Other child restraint models and types (such as non-integral child restraints) may also have led to different results. Nevertheless, these experiments suggest that, on the whole, the side impact test in UN Regulation 129 is reasonably similar to a typical side impact collision. Child restraint systems have changed markedly over the last 10 to 15 years, such that most now display characteristics that would be expected to improve protection in the event of a side impact collision (such as deeper side wings and energy-absorbing padding). These features have been implemented with no regulatory test for side impact (in UN Regulation 44), although test procedures have been developed over this period by ISO (International Organisation for Standardisation) and by the NPACS (New Programme for the Assessment of Child restraint Systems) consortium. Evidence for the efficacy of these features in real-world collisions is hard to find, not least because there is limited information about trends in the performance of child restraints over time. Nevertheless, it seems likely that these features would improve the performance of child restraints (over those with minimal side wings or padding). It would be desirable, therefore, for the regulatory test to enable these features to be optimised. Our experiments indicated that the test procedure would encourage these features in rear-facing child restraints. However, forward-facing child restraints may be able to meet the requirements specified in UN Regulation 129 without such features, or at least with degraded features compared with those on the market now. Specifying additional design requirements in UN Regulation 129 might reduce the risk of degradation, if it becomes apparent that such features are not needed to meet the performance requirements in the sled test.

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6

Conclusions

6.1

Non-integral ISOFIX child restraint systems: performance criteria and test methods

1. Injuries to children in non-integral child restraint systems tend to occur to the head, chest and abdomen. a. Enhancing the performance of non-integral child restraint systems in these body regions (while maintaining performance elsewhere) may reduce injuries; however, there are too few representative collision data with children to quantify the benefits statistically. 2. The interaction between the Q-Series and the lap part of the seat belt can be improved with accessories to prevent belt intrusion. a. Different accessories have been developed by different organisations for different Q-Series dummies and hence a consistent solution needs to be agreed across the Q-Series range. b. Further comparative experiments would be needed to determine which accessory was the most suitable for use with the Q-Series dummies in UN Regulation 129. 3. The front impact test procedure did not distinguish between two non-integral child restraints with seemingly different characteristics for abdominal protection and may not, therefore, improve the performance of non-integral child restraints. It might be that: a. The characteristics for abdominal protection (lap belt guides) were not as important as was assumed; b. The test procedure arrangement (seat cushion, belt anchorages, dummy positioning) was more important than the child restraint features; c. The dummy was not sensitive to the differences between the child restraints, due to the design characteristics of its pelvic and lumbar regions. 4. Adapting the dummy installation procedure along the lines proposed by UMTRI for FMVSS213 may improve the sensitivity of the front impact test procedure to the characteristics of non-integral child restraints. 5. The front impact test procedure would encourage improvements in the abdominal protection provided by impact shields, if the abdominal pressure sensors are specified in UN Regulation 129 (with a reasonable performance threshold). 6. Movement of the diagonal belt towards the neck seems to be a product of the torso design of the Q-Series dummies that cannot be prevented by simply adapting the test procedure. a. Movement of the belt reduces the contribution made by the child restraint in keeping the dummy within the belt and minimising head excursion. b. Movement of the belt takes it away from the chest deflection sensor before the peak restraint forces are applied to the chest.

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7. The head of the Q-Series tends to strike the chest directly above the deflection sensor resulting in a large peak in the chest deflection response. a. Excluding this period of loading would provide a more meaningful measurement of chest deflection (albeit with the limitations mentioned above). 8. Movement of the belt reduces the value of chest deflection as a (potential) performance requirement for the assessment of non-integral child restraints, although this could be mitigated by fitting a (second) chest deflection sensor to the Q-Series dummies. a. This second sensor, positioned higher on the chest, would also help to reduce the influence of head-to-chest contact.

6.2


1. The majority of front impact collisions involving children occur: up to 50 km/h; with a purely longitudinal (i.e. 12 o’clock) direction of force; and with loading to both longitudinal members (particularly for serious injuries). a. It would be preferable, therefore, for the front impact test pulse in UN Regulation 129 to replicate these characteristics, which would increase the severity of the test marginally. b. Very few children are injured in collisions that are more severe than this so a more substantial change in severity does not appear to be justified, at least from our limited representative collision data. 2. The front impact pulse in UN Regulation 129 is less demanding of a restraint system than the pulse of modern (supermini) cars under the same conditions (50 km/h, full-width collision). 3. The front impact pulse can underestimate dummy loads such that a child restraint passes the test, when it would otherwise fail (under more representative conditions).

6.3


1. There is very limited representative data with enough depth to identify (with any statistical confidence) needs and priorities for improving the performance of child restraint systems. a. Although child restraint systems undoubtedly perform very well in most collisions, the sparse data does not necessarily mean that the serious injury problem is small for children across the European Union; 2. Evidence-based injury criteria and thresholds are available for use with the Q-Series dummies in front impact test procedures, although further work is needed to complete the thresholds for chest deflection and abdominal pressure. a. A task force is underway to perform further accident reconstruction experiments and to enhance the injury risk curves for chest deflection and abdominal pressure.

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3. Head injury criteria and performance thresholds are available for use with the Q Series in side impact; limited data were available from which to derive injurybased thresholds for other body regions.

6.4

The side impact test conditions

1. The side impact test conditions in UN Regulation 129 are reasonably similar to a car-to-car side impact collision. 2. The side impact test is sensitive to differences between child restraints, but forward-facing restraints can met the requirements of the test with minimal features for side impact protection.

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information and services on the subject of accident analysis for the development of legislation on frontal impact protection (Client Project Report 815). Retrieved November 12, 2012 from: http://ec.europa.eu/enterprise/sectors/automotive/documents/calls-fortender-and-studies/index_en.htm Schnottale, B., Lorenz, B., Verheyen, C. and Zellmer, H. (2011). A comparison of the Q6 and the HIII 6 years old dummy in frontal impact tests in a car environment involving different CRS and seat belt systems. In: Proceedings of the Ninth International Conference Protection of Children in Cars, 1-2 December 2011, Munich, Germany. Munich, Germany: TÜV SÜD. Tylko, S. and Bussières, A. (2012). Responses of the Hybrid III 5th female and 10-yearold ATD seated in the rear seats of passenger vehicles in frontal crash tests. In: IRCOBI Conference Proceedings, 12-14 September 2012, Dublin, Ireland. Zurich, Switzerland: International Research Council on Biomechanics of Injury (IRCOBI). Visvikis, C., Carroll, J. A., Hynd, D., Pitcher, M., Barrow, A., and Broertjes, P. (2012). Research for optimised evolution of the new regulation on enhanced child restraint systems. In: Proceedings of the 10th International Conference Protection of Children in Cars, 6-7 December 2012, Munich, Germany. Munich, Germany: TÜV SÜD. Visvikis, C. and Le Claire, M. (2003). Child occupant protection – final report (Report No. PR SE/851/03). Unpublished client report, TRL. Visvikis, C., Le Claire, M., Carroll, J. A., Cheung, G., and Hynd, D. (2008). A UK perspective on the status of the Q-Series dummy and its potential for use in regulatory testing. In: Proceedings of the 6th International Conference Protection of Children in Cars, 1-2 December 2008, Munich, Germany. Munich, Germany: TÜV SÜD. Visvikis, C., Pitcher, M., Girard, B., Longton, A. and Hynd, M. (2009). Literature review, accident analysis and injury mechanisms. EPOCh Project Deliverable, Work Package 1, Task 1. Retrieved October 18, 2012 from: http://www.epochfp7.org/Publications.aspx Wismans, J., Waagmeester, K., Le Claire, M., Hynd, D., de Jager, K., Palisson, A., van Ratingen, M., and Troisseille, X. (2008). Q-dummies report: advanced child dummies and injury criteria for frontal impact. Retrieved November 8, 2012 from: http://eevc.org/publicdocs/publicdocs.htm

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Annex 1 – In-depth collision data analysis

Annex 1: Analysis of in-depth representative collision databases 1

Introduction and analysis methods

Information derived from studying real-world collisions forms the basis for most countermeasures to reduce the number of deaths and injuries that occur on European roads. There are two main types of data, often described as macro and micro data. Macro data refers to information collected at a national or an international level. The level of detail recorded is normally sufficient to describe the overall characteristics of the collision and the injured casualty population, but because of the vast number of incidents which occur, it is not practical for much more than an overview of the key facts to be documented. Micro, or in-depth, data enable the findings of detailed investigations to be combined and reviewed, thus enabling a greater understanding of the causes and consequences of collisions to be developed. When it comes to children, macro datasets, such as CARE (Community database of Accidents on the Roads of Europe) do not contain information about the use of child restraint systems. This limits their value for studies of child injury mechanisms and priorities for protection. Micro datasets typically contain this information, but the sampling strategies used can mean that relatively few children are included (from a statistical point of view at least). This project used real-world collision data from two indepth databases to underpin the principal aims and activities: i.

GIDAS (German In-Depth Accident Study) - GIDAS investigates collisions resulting in at least one injured person within defined areas of Hannover and Dresden. The collisions are selected using a statistical sampling plan. GIDAS data analysis was provided by VUFO GmbH.

ii.

CCIS (Co-operative Crash Injury Study) – CCIS investigated collisions (from 1983 to 2010) in various locations in England. The collisions were selected in a way that favoured those in which the car occupants were fatally or seriously injured.

Although a number of institutions run small-scale studies, GIDAS and CCIS are the two main in-depth, representative databases available in Europe. This Annex describes the analysis of GIDAS and CCIS. The specific objectives were to: i.

Investigate whether the front impact crash pulse specified in UN Regulation 129 is still appropriate, in light of changes in the characteristics of vehicles that may have occurred since the introduction of offset crash testing in legislation and Euro NCAP;

ii.

Investigate the injuries that children receive in front and side impact collisions in order to highlight which body regions need to be protected and hence where the regulatory performance evaluation should be targeted

iii.

Review, in detail, the injuries to children in non-integral child restraint systems with a view to supporting the development of test methods and assessment criteria in UN Regulation 129;

Further information on GIDAS and CCIS is included in Appendices B and C, including an overview of the respective sample characteristics, representativeness and definitions and

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terminology. The nature and characteristics of these two studies are different and the data analysis reflects this, with GIDAS providing German national weighted figures, whereas the CCIS results are simply child casualty counts. Therefore, interpretation and comparison of the data is based on trend and pattern assessment rather than absolute quantification. Children in the GIDAS and CCIS databases were selected for analysis if they were 12 years old or less and were passengers in cars manufactured in 2000 or later.

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2 2.1

The characteristics of front impact collisions involving children Impact speed

The majority of the children in the CCIS and GIDAS samples experienced a change of velocity (Δv) of 50 km/h or less. This is shown in Table 13 (for the CCIS sample) and Table 14 (for the GIDAS sample). Table 13: CCIS - change of velocity (Δv) by injury group Δv (km/h) Injury group

Total

110

1120

2130

3140

4150

5160

6170

7180

8190

91100

N/K

MAIS=0-1

177

1

18

23

18

12

0

1

0

0

0

104

MAIS=2 (survived)

14

0

0

1

1

5

0

1

0

0

0

6

MAIS≥3 (survived)

12

0

0

0

2

1

0

1

0

0

0

8

0

0

0

0

0

0

0

0

0

0

0

0

40

0

5

5

4

0

0

0

0

0

0

26

243

1

23

29

25

18

0

3

0

0

0

144

Fatal Not known (N/K) Total

Table 14: GIDAS - change of velocity (Δv) by injury group Δv (km/h) Injury group

Total

110

1120

2130

3140

4150

MAIS=0-1

174,8

36,8

50,2

47,0

24,0

13,6

2,4

0,8

-

-

-

MAIS=2 (survived)

7,2

-

4,2

2,6

0,5

-

-

-

-

-

-

MAIS≥3 (survived)

1,6

-

0,8

-

-

-

-

0,8

-

-

-

Fatal

0,6

-

-

-

-

-

-

-

-

-

0,6

Not known

5,8

2,1

1,3

0,8

1,7

-

-

-

-

-

-

190,1

38,9

56,5

50,3

26,2

13,6

2,4

1,6

-

-

0,6

Total

5160

6170

7180

8190

91100

Because there were significant numbers of children in the CCIS sample whose change of velocity was not known (144 children), the Equivalent Test Speed (ETS) and Equivalent Energy Speed (EES) were also examined. ETS (used in CCIS) and EES (used in GIDAS) are subtly different from each other (see Appendix A), but for this exercise they provide comparable benchmarks or descriptions of the distribution of the impact speeds that the children experienced. Table 15 shows the ETS by injury group for the CCIS sample and Table 16 shows the EES by injury group for the GIDAS sample.

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Table 15: CCIS - ETS by injury group ETS (km/h) Injury group

Total

110

1120

2130

3140

4150

5160

6170

7180

8190

91100

N/K

MAIS=0-1

177

7

36

53

32

7

2

1

0

0

0

39

MAIS=2 (survived)

14

0

0

4

4

3

0

1

0

0

0

2

MAIS≥3 (survived)

12

0

0

0

5

2

2

1

0

0

0

2

0

0

0

0

0

0

0

0

0

0

0

0

40

0

12

12

7

1

0

0

0

0

0

8

243

7

48

69

48

13

4

3

0

0

0

51

Fatal Not known (N/K) Total

Table 16: GIDAS - EES by injury group EES (km/h) Injury group

Total

110

1120

2130

3140

4150

MAIS=0-1

174,8

16,8

83,2

41,8

20,2

MAIS=2 (survived)

7,2

-

2,9

3,3

MAIS≥3 (survived)

1,6

-

-

Fatal

0,6

-

184,2

16,8

Total

5160

6170

7180

8190

91100

10,9

-

0,8

1,2

-

-

1,0

-

-

-

-

-

-

0,8

-

-

-

0,8

-

-

-

-

-

-

-

-

-

-

0,6

-

86,1

46,0

21,1

10,9

-

1,6

1,2

0,6

-

The impact speed or change of velocity that the children in the British and German studies commonly experience is below 51 km/h: i.

Seven of the 192 children in the CCIS sample experienced an ETS of 51km/h or more, where the ETS was known;

ii.

4,6 of the weighted 190,1 children in the GIDAS sample experienced a velocity change of 51km/h or more.

2.2

Direction of force

The direction of the impact force experienced by cars and their occupants is a key parameter to replicate in any regulation testing. The distribution of the Principal Direction of Force (PDF), where 12 o’clock refers to a head-on collision, is shown for the CCIS sample in Table 17 and for the GIDAS sample in Table 18.

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Table 17: CCIS - PDF by injury group Injury group

Total

PDF (o’clock) 10

11

12

1

2

Other

MAIS=0-1

177

5

19

115

34

2

2

MAIS=2 (survived)

14

0

1

10

3

0

0

MAIS≥3 (survived)

12

0

1

10

1

0

0

0

0

0

0

0

0

0

40

0

9

22

8

1

0

243

5

30

157

46

3

2

Fatal Not known Total

Table 18: GIDAS - PDF by injury group Injury group

Total

PDF (o’clock) 10

11

12

1

2

Other

MAIS=0-1

174,8

5,1

43,2

91,7

18,9

13,0

2,9

MAIS=2 (survived)

7,2

-

1,1

3,2

-

2,9

-

MAIS≥3 (survived)

1,6

-

-

1,6

-

-

-

Fatal

0,6

-

-

0,6

-

-

-

184,2

5,1

44,3

97,1

18,9

15,9

2,9

162

5

42

86

16

11

2

Total (weighted) Total (unweighted)

The majority of the children involved in frontal car impacts in both datasets experienced a head-on impact +30° (11 to 1 o’clock), with over the half having a PDF of 12 o’clock (65 per cent and 53 per cent of the CCIS and GIDAS data respectively).

2.3

Vehicle overlap and longitudinal loading

The investigation considered the pattern of damage to the front of the cars and specifically the amount of direct contact and engagement across their front structures. It concluded that there was a reasonable distribution of damage, with some cars experiencing very low percentage overlaps, right through to those with 100 per cent of the front structure loaded; there was a bias towards full overlap crashes, especially for the more seriously injured children. Another way to investigate the damage pattern is to consider the car longitudinal loading. The distribution of loading experienced by the vehicle’s longitudinal beams in the collision for each injury group for each dataset is shown in Table 19 (CCIS) and in Table 20 (GIDAS). For CCIS, 13 of the 26 children with MAIS>2 injuries were seated in vehicles with direct loading to both longitudinals; similarly for GIDAS, over 60 per cent of the weighted MAIS>2 child casualties experienced direct loading to both longitudinals.

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Table 19: CCIS – Pattern of longitudinal loading by injury group Longitudinal loading Injury group

Total

No direct loading

Direct loading to NS, not OS

Direct loading to OS, not NS

Direct loading to both NS and OS

MAIS=0-1

177

40

35

57

45

MAIS=2 (survived)

14

1

0

7

6

MAIS≥3 (survived)

12

1

3

1

7

0

0

0

0

0

40

7

13

10

10

243

49

51

75

68


Table 20: GIDAS – Pattern of longitudinal loading by injury group Longitudinal loading Injury group

MAIS=0-1

Total

Direct loading to NS, not OS

No direct loading

Direct loading to OS, not NS

Direct loading to both NS and OS

174,8

38,2

35,9

32,9

67,8

MAIS=2 (survived)

7,2

-

1,8

-

5,5

MAIS≥3 (survived)

1,6

-

0,8

0,8

-

Fatal

0,6

-

-

-

0,6

184,2

38,2

38,5

33,7

73,8

162

32

35

28

67

Total (weighted) Total (unweighted)

2.4

Comparison of collisions with UN Regulation 129 front impact test conditions

Each collision in the GIDAS and CCIS sample was grouped according to whether it was either: i.

Covered by UN Regulation 129; or

ii.

More severe than UN Regulation 129.

The categorisation was based on the velocity change (Δv) and the percentage overlap of damage to the car front structure. Children who experienced a Δv ≥ 50 km/h and an overlap ≥ 10 per cent, were judged to have had a crash that was more severe than the front impact test conditions in UN Regulation 129. It should be noted that this was a somewhat subjective method and there were some limitations with regards to the precision of the outcome. However, it was a relatively straightforward way to assess the likely number of children who were ‘covered’ by the UN Regulation 129 test conditions. The findings are shown in Table 21 (CCIS) and Table 22 (GIDAS).

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Table 21: CCIS – Children covered by UN Regulation 129 test conditions Comparison with UN Regulation 129 Injury group MAIS=0-1

Total

Covered by UN Regulation 129

More severe than UN Regulation 129

N/K

177

135

3

39

MAIS=2 (survived)

14

11

1

2

MAIS≥3 (survived)

12

7

3

2

0

0

0

0

40

31

0

9

243

184

7

52


Table 22: GIDAS - Children covered by UN Regulation 129 test conditions Comparison with draft UN Regulation on CRS Injury group

MAIS=0-1

Total

Covered by UN Regulation 129

More severe than UN Regulation 129

174,8

171,6

3,2

MAIS=2 (survived)

7,2

7,2

-

MAIS≥3 (survived)

1,6

0,8

0,8

Fatal

0,6

-

0,6

184,2

179,7

4,6

Total

The principal variable used in the assessment of whether or not the collision was covered by UN Regulation 129 was the impact severity, and most collisions in the real-world datasets reviewed by this study had a Δv less than 50 km/h. The real-world data indicate that the incidence of car crashes involving child occupants with a Δv of over 50 km/h, and classified as more severe than UN Regulation 129, is small. However, the relative proportion of seriously injured children (MAIS=2 and MAIS≥3) within these more severe collisions is far greater compared to those, that by the definition presented here, are likely to be covered by UN Regulation 129. The CCIS and GIDAS samples suggest that although the risk of serious and severe injury is higher for those crashes over 50 km/h, the absolute number of casualties suggests most seriously injured child car occupants experience a crash covered by UN Regulation 129, although this analysis does not take account of the appropriate restraint type.

2.5

2.5.1

Collisions more severe than UN Regulation 129 front impact test conditions Restraint type in collisions more severe than UN Regulation 129

For those children judged to have experienced a collision more severe than the front impact test conditions in UN Regulation 129, the nature of their type of restraint is shown in Table 23 (CCIS) and Table 24 (GIDAS). These data indicate that where children experienced an injury collision more severe than UN Regulation 129, their restraint type was typically a child restraint system.

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Table 23: CCIS – Restraint type for collisions more severe than UN Regulation 129 Restraint type Injury group

Child restraint system

Total

Adult seat belt

Unrestrained

Not known

MAIS=0-1

3

1

1

0

1

MAIS=2 (survived)

1

1

0

0

0

MAIS≥3 (survived)

3

2

1

0

0

Fatal

0

0

0

0

0

Not known

0

0

0

0

0

Total

7

4

2

0

1

Table 24: GIDAS – Restraint type for collisions more severe than UN Regulation 129 Restraint type Injury group

Total


Adult

Restrained

seat belt

NFS

Unrestrained

Unknown

MAIS=0-1

3,2

3,2

-

-

-

-

MAIS=2 (survived)

-

-

-

-

-

-

MAIS≥3 (survived)

0,8

0,8

-

-

-

-

Fatal

0,6

0,6

-

-

-

-

Total

4,6

4,6

-

-

-

-

2.5.2

Case-by-case analysis and review of potential countermeasures

A cases-by-case review of the children (in the CCIS and GIDAS databases) involved in collisions more severe than the front impact test conditions in UN Regulation 129 was undertaken to identify the injury mechanisms and potential countermeasures. There were limited cases to scrutinise, but examples of the injury mechanisms are given below. Example 1: A forward-facing, one year old child, sustained concussion and minor injuries to their face from contact with the rear of the seat in front. Their integral child restraint (with a five-point harness) was attached with the three-point seat belt (confirmed by marks on the buckle). The child’s car experienced an ETS of 67 km/h (with an overlap of 65 per cent), but there was no intrusion in the child’s seating position. It seems feasible, therefore, to provide protection at this severity; for instance, the impact speed in the front impact Euro NCAP test is 64 km/h (with an overlap of 40 per cent). It should also be noted that UN Regulation 129 extends the use of rear-facing child restraints to 15 months and this may have been an effective countermeasure in this case (notwithstanding the higher severity of the crash). Example 2: A forward-facing, two year old child, received brain injuries from contact with the rear of the seat in front. The integral child restraint (with a fiveTRL

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point harness) was attached with the three-point seat belt. The child’s car experienced an ETS of 59 km/h (with an overlap of 100 per cent), but there was no intrusion in the child’s seating position. Once again, it seems feasible to provide protection at this severity. No significant failure of the child restraint system was observed by the collision investigators, but significant movement of the child restraint and/or the child must have taken place for the head contact to have occurred. The severity of the collision may have played a role, but it was also possible that the child restraint or the integral harness were not adjusted tightly. Example 3: A five year old child using a booster seat (with the three-point seat belt) in the rear of a car received a fractured clavicle and pulmonary contusion. The injuries were attributed to loading from the seat belt. This was case C6 in Section 4.1. Example 4: In a case that was very similar to example 3, a six year old child using a booster seat fractured their clavicle and received an abdominal vein fissure under loading from the seat belt. This was case G8 in Section 4.1. Although each of these collisions was relatively severe (60 – 70 km/h), the passenger compartment did not intrude into the child’s seating position and their child restraint system was not damaged significantly. In these circumstances, it seems likely that serious injuries would be preventable through better restraint design (for the severity). The cases can be divided into two groups: For Examples 1 and 2: These children received head injuries (due to head contact) in vehicles with a reasonable amount of ‘excursion space’ in front of them. Assuming the child restraints were installed correctly and with appropriate tension in each seat belt and integral harness, the injuries occurred because the child restraints were unable to limit head excursion at these higher collision severities (compared with UN Regulation 44 / 129). Testing child restraints to a higher severity might improve their capacity to limit head excursion in more severe collisions; however, care would be needed to avoid unintended consequences (such as stiffer restraints) for lower severity collisions, which are much more common. For Examples 3 and 4: These children received shoulder and chest injuries from the restraint forces applied to their torso by the seat belt. The injuries occurred because the magnitude of the forces, which was a function of the collision severity, exceeded the tolerance levels of these children. Assuming that the booster seats were used correctly and already provided an optimum path for the seat belt, testing child restraints at a higher severity may not be a feasible countermeasure (because there may be limited scope for booster seats to manage these forces further). Load-limiting rear seat belts, with a pretensioner, could have been beneficial for these cases. However, there are practical limitations with respect to a realistic magnitude of force which would be practical for children, whilst being compatible with larger (teenager and adult) rear passengers. To be an effective solution, this countermeasure may require intelligent or adaptive seat belts and possibly airbags.

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2.6

Summary and principal findings

This section reviewed the real-world injury experience of child car occupants and compared this with the front impact test conditions in UN Regulation 129. The main findings were: 1. There is limited real-world data with enough depth and breadth of information to comprehensively quantify how well the front impact pulse represents the characteristics of modern vehicles and the type of collisions involving injured children. In-depth studies from Germany and Great Britain provided some data, but the respective sample sizes were small and it cannot be assumed they describe the injury experience for the EU27. However, from the data available, it is likely that: a. Most crashes involving child car occupants occur at speeds less than 50km/h; b. The direction of the force in a frontal impact is typically head-on; c. There is a bias towards full overlap crashes, especially for the more seriously injured children. 2. The children were grouped as either involved in collisions ‘covered by UN Regulation 129 or ‘more severe than UN Regulation 129’. This is by its nature a subjective exercise and oversimplifies a number of factors, perhaps most importantly the shape and magnitude of the crash pulse, which is not known from the collision data. However it does help to quantify target populations, albeit at a high level. For CCIS and GIDAS data, the majority of injured children using this technique were found to be ‘covered by UN Regulation 129’. 3. For the children who were grouped as experiencing collisions ‘more severe than UN Regulation 129’: a. The risk of serious and severe injury is higher for those crashes over 50km/h. However, most seriously injured child car occupants experience a crash covered by UN Regulation 129. b. For the seriously injured (MAIS≥2) children, testing child restraints at a higher severity (60-70 km/h) might be beneficial for some children, provided it doesn’t reduce performance at lower severities. However, a more severe test might not be beneficial for some injury mechanisms and it seems likely that better restraint of older children, than currently afforded by adult three-point seat belts (even when combined with nonintegral child restraint systems), would be a more effective countermeasure.

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3

Injuries to children and priorities for protection in frontal and side impacts

3.1

Body region injured for children with MAIS≥2 injuries – all restraint types

3.1.1

Front impact

Table 25 (CCIS) and Table 26 (GIDAS) show the distribution of AIS≥2 injuries by body region for each restraint type (broken down by seating position) in front impact collisions. The sample sizes are relatively small and therefore some caution is required when interpreting the findings. The CCIS and GIDAS data highlight that the body regions which are seriously injured most often are the head, chest, abdomen and arms. The CCIS database has examples of pelvis, leg and neck injuries. Table 25: CCIS – Front impact – Body region injured by restraint type Restraint type

Seating position

Body region injured (AIS≥2) Total

Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

3

1

0

0

0

1

0

1

14

5

1

1

4

2

1

0

8

1

0

4

2

0

0

1

Rear

20

2

2

1

7

5

2

1

Unrestrained

Both

2

0

0

1

0

1

0

0

Not known

Both

2

0

0

0

2

0

0

0

49

9

3

7

15

9

3

3


Adult seat belt

Front Rear Front

Total

Table 26: GIDAS – Front impact – Body region injured by restraint type Restraint type

Seating position


Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

-

-

-

-

-

-

-

-

6,8

2,8

1,1

1,3

1,3

-

-

-

-

-

-

-

-

-

-

Rear

1,8

1,8

-

-

-

-

-

-

Unrestrained

Both

2,4

2,4

-

-

-

-

-

-

Not known

Both

2,9

2,9

-

-

-

-

-

-

13,7

9,9

1,1

1,3

1,3

-

-


Adult seat belt

Total

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3.1.2

Side impact

Table 27 (CCIS) and Table 28 (GIDAS) show the distribution of AIS≥2 injuries by body region for each restraint type (broken down by seating position) in side impact collisions. Once again, the sample sizes are small and therefore care should be applied when interpreting the tables. The CCIS and GIDAS data highlight that the body regions which are seriously injured most often are the head, chest, abdomen and legs. Table 27: CCIS – Side impact – Body region injured by restraint type Restraint type

Seating position


Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

Front

0

0

0

0

0

0

0

0

Rear

5

2

0

1

0

1

0

1

Front

1

1

0

0

0

0

0

0

Rear

5

2

0

1

0

1

1

0

Unrestrained

Both

1

0

0

0

0

0

0

1

Not known

Both

3

2

0

0

0

0

0

1

15

7

0

2

0

2

1

3


Adult seat belt

Total

Table 28: GIDAS – Side impact – Body region injured by restraint type Restraint type

Seating position


Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

Front

0,8

0,8

-

-

-

-

-

-

Rear

2,8

2,8

-

-

-

-

-

-

Front

0,5

0,5

-

-

-

-

-

-

Rear

4,0

-

-

1,3

-

1,3

-

1,3

Unrestrained

Both

-

-

-

-

-

-

-

-

Not known

Both

-

-

-

-

-

-

-

-

8,2

4,1

-

1,3

-

1,3

-

1,3


Adult seat belt

Total

3.2

3.2.1

Body region injured for children with MAIS≥2 injuries – child restraint systems only Front impact

Table 29 (CCIS) and Table 30 (GIDAS) show the distribution of AIS≥2 injuries by body region for each type of child restraint system in front impact collisions. The sample sizes are small and care is required when interpreting the findings. The CCIS and GIDAS data highlight that the body regions which are seriously injured most often for all ages of children using child restraint systems are the head, abdomen, arms and chest.

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Table 29: CCIS – Front impact – Body region injured by restraint type Body region injured (AIS≥2) Child restraint system

Total

Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

Integral (RF)

0

0

0

0

0

0

0

0

Integral (FF) with harness

6

2

0

1

2

1

0

0

Integral (FF) with shield

0

0

0

0

0

0

0

0

Non-integral with backrest

5

3

0

0

0

1

0

1

Non-integral without backrest

4

1

1

0

0

1

1

0

Not known

2

0

0

0

2

0

0

0

17

6

1

1

4

3

1

1

Total

Table 30: GIDAS – Front impact – Body region injured by restraint type Body region injured (AIS≥2) Child restraint system

Total

Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

Integral (RF)

0,6

0,6

-

-

-

-

-

-


0,5

0,5

-

-

-

-

-

-

-

-

-

-

-

-

-

-

5,6

1,8

-

1,1

1,3

1,3

-

-


-

-

-

-

-

-

-

-

Not known

-

-

-

-

-

-

-

-

6,7

2,8

-

1,1

1,3

1,3

-

-

Integral (FF) with shield Non-integral with backrest

Total

3.2.2

Side impact

Table 31 (CCIS) and Table 32 (GIDAS) show the distribution of AIS≥2 injuries by body region for each type of child restraint system. The sample sizes are small and care is required when interpreting the findings. The CCIS and GIDAS data highlight that the body region which is seriously injured for all ages of children using a child restraint is the head. Other body regions will be vulnerable to injury in side impacts, but there simply are not the in-depth cases that meet the sample criteria to review at this time.

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Table 31: CCIS – Side impact – Body region injured by restraint type Body region injured (AIS≥2) Child restraint system

Total

Head

Neck

Chest

Arms

Abdomen

Pelvis

Legs

Integral (RF)

0

0

0

0

0

0

0

0


5

2

0

1

0

1

0

1

Integral (FF) with shield

0

0

0

0

0

0

0

0

Non-integral with backrest

0

0

0

0

0

0

0

0


0

0

0

0

0

0

0

0

Not known

0

0

0

0

0

0

0

0

Total

5

2

0

1

0

1

0

1

Table 32: GIDAS – Side impact – Body region injured by restraint type Body region injured (AIS≥2) Child restraint system

Total

Head

Neck

Chest

Arms

Abdomen

Pelvis

-

-

-

-

-

-

-

-

1,1

1,1

-

-

-

-

-

-

-

-

-

-

-

-

-

-

1,6

1,6

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Not known

1,0

1,0

-

-

-

-

-

-

Total

3,7

3,7

-

-

-

-

-

-

Integral (RF) Integral (FF) with harness Integral (FF) with shield Non-integral with backrest Non-integral without backrest

3.3

Legs


There is limited in-depth and representative real-world data available to analyse, that correlates the collision circumstances, the vehicle damage, the type of restraint used and its performance and the injuries the child suffered. This data is required to be able to describe the injury mechanisms and highlight which body regions body regions need to be protected and where the regulatory performance evaluation should be targeted. However, it cannot be concluded that because the representative in-depth data is sparse at best with respect to describing child car occupant casualties, mainly because it is limited to two countries that routinely collect the information, that the child injury problem is small. In contrast, national casualty data shows that significant numbers of child car occupants are injured or killed every year in Europe, and other studies have highlighted typical injuries that are commonly suffered (Kirk, 2012; Wismans et al., 2008). An assessment of the CCIS and GIDAS datasets was not able to statistically quantify which body regions need to be protected. However, there were clear trends and for targeting the regulatory performance evaluation. It was found for all impact types and restraints that there is good evidence that the focus should be on the protection of the head, chest and abdomen.

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4


4.1

Case-by-case analysis of children in non-integral child restraints

A detailed case-by-case analysis of the CCIS and GIDAS datasets was undertaken to understand the injuries received by children in non-integral child restraint systems, their mechanisms and the potential countermeasures that might have improved the outcome. Table 33 provides a summary of the reviewed cases, involving children who were: i.

Using a non-integral child restraint system; in a

ii.

Frontal impact; and

iii.

Sustained MAIS>2 injuries.

There were 10 children who met the selection criterion, seven from CCIS (cases C1 to C7) and three from GIDAS (cases G8 to G10). Each case was studied in detail and an overview of each is provided below along with potential countermeasures. C1

Booster cushion; 8 year old; MAIS=2, head injury (deep laceration) The child’s head injury was likely to have resulted from contact with the rear of the seat in front. The velocity change (32 km/h) was less than the impact speed specified in UN Regulation 44 (50 km/h). Furthermore, measurements made inside the car by the collision investigators showed that the space in front of the child was greater than the head excursion limit in the regulation. Therefore, a booster cushion (when used correctly) would be expected to limit head excursion sufficiently to prevent head contact in these conditions. The booster cushion used in the collision was equipped with a diagonal belt clip attached to a length of adjustable cord. It was unclear whether this clip was used or not, although there was no evidence for any major misuse of the diagonal belt. Countermeasure: Reducing the child’s head excursion would be the main countermeasure in this collision. However, it was unclear whether the head injury occurred due to poor performance of the booster cushion or due to misuse.

C2

Booster seat; 5 year old; MAIS=2, right upper arm fracture The car experienced a frontal followed by (left) side impact and it was unclear to the collision investigators which impact caused the child’s (right) upper arm fracture. However, given that the arm fracture occurred on the opposite side from the side impact, it seems likely to have resulted from excessive arm movement or “flailing” (regardless of which impact ultimately led to the injury). Countermeasure: It is difficult to prevent the arms from flailing, particularly in complex collisions. A child restraint with deeper side wings and energy absorbing padding may have helped to keep the arms in position.

C3

Booster seat; 6 year old; MAIS=3, left leg fractures The child was seated in the front passenger seat and it appears that their lower leg injuries resulted from contact with the facia panel. There was no significant

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intrusion, but the passenger seat was loaded "downwards" with damage to the mountings and runner. Countermeasure: The child’s injuries occurred because the displacement of their lower legs was greater than the space between the child and the stiff facia panel. It might be possible to encourage better child restraint performance in this regard, by specifying a limit for leg (or foot) excursion in UN Regulation 129; however, the space in the car may have been a factor in this case (depending on the front seat adjustment). More space may have been available in the rear of the car and there would have been fewer rigid structures in front of the child. C4

Booster seat; 3 year old; MAIS=2; head injury (skull fracture) The child’s skull fracture was caused by contact with a deformed B-pillar and door frame in this severe front impact (with a heavy goods vehicle). The distance from the child’s position to the contact site was not recorded, and it may have been less than the performance requirement for head excursion in UN Regulation 44. Countermeasure: A three year old child may have experienced less head excursion if they were seated in an ISOFIX integral child restraint system with a five-point harness. However, the impact conditions may also have been challenging for an integral child restraint due to the level of deformation observed in the passenger compartment. It seems likely that improved vehicle compatibility with heavy vehicles may have been the most effective countermeasure.

C5

Booster cushion; 7 year old; MAIS=4; neck injury (fracture/dislocation) The collision investigators concluded that the booster cushion was misused in this collision, with the “upper portion (diagonal part) of the seat belt tucked under the arm of the booster cushion”. They found marks on the seat belt and on the booster cushion that appeared to verify this assumption. This would essentially create a ‘double’ lap belt, leaving the torso unrestrained. The child received serious neck injuries, which were attributed to the diagonal belt webbing slipping off the booster cushion during the impact and restraining the chest and neck very abruptly. Abrasions found on the child’s neck (front left) and chest (upper right) might support this proposed mechanism, although marks in these locations might also occur when a seat belt is used correctly. Another potential source of the neck injuries might have been head contact with the rear of the seat in front, but there was no evidence for such contact, either in the vehicle, or on the child. Countermeasure: If the booster cushion was misused, as suspected by the collision investigators, the child’s injuries may have been prevented by simply using it correctly.

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Table 33: Case-by-case analysis of children in non-integral CRS Case

Age yrs

Seating position6 & CRS

PDF/ Δv (km/h)

Overlap (%)7

Injury description & mechanism Body region

AIS

Injury

Injury mechanism

C1

8

RNS – Booster cushion

12/32

100

Head

2

Deep laceration with debridement on face

Contact with the front seat- back

C2

5

RNS – Booster seat

12/35

48

R arm

2

Fractured humerus with displacement

Contact with vehicle interior

C3

6

FSP Booster seat

12/39

100

3

Displaced closed fracture of tibia

Contact with facia panel

2

Fractured distal fibula

ROS – Booster seat

12/-

Head

2

Skull (parietal bone) fracture

Contact with intruded Bpillar

Neck

4

Incomplete cord syndrome – fracture and dislocation of C2/C3

Seat belt webbing with suspected child restraint misuse

Abdomen

2

Duodenal contusion

Pelvis

2

Fractured iliac wing

L Arm

2

Clavicle fracture

Thorax

3

Lung contusion

2

Fractured frontal skull

2

Traumatic subarachnoid haemorrhage

Abdomen

2

Liver contusion

Arm

2

Clavicle fracture

Abdomen

3

Abdominal vein fissure

Head

5

Traumatic brain injury, Grade III

Neck

2

Dens fracture

Upper arm

2

Clavicle fracture

Thorax

4

Lung contusion

2

Liver laceration

2

Kidney rupture

2

Pancreas rupture

2

Traumatic brain injury, Grade I

C4

C5

C6

C7

G8

G9

3

7

5

3

6

5

RNS – Booster Cushion




R99 – Booster seat

12/-

12/59

65

L leg

29

100

Seat belt webbing

Head 12/40

12/68

12/94

63

47

47

Abdomen

G10

6

5

R99 – Booster Cushion

12/26

96

Seat belt webbing

Head

Contact with the front N/S seat-back

Seat belt webbing

Seat belt webbing

Head contact with the front seat-back

Seat belt webbing


FSP – Front Seat Passenger; RNS – Rear Nearside Passenger; ROS – Rear Offside Passenger; R99 – Rear

Seat, side not known. 7

Percentage of direct contact damage to front structure of the car.

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C6

Booster seat; 5 year old; MAIS=3; chest injury (lung) The child’s injuries resulted from the restraint forces that were applied to their chest by the seat belt. The magnitude of these forces exceeded the child’s tolerance threshold, which led to their clavicle fracture and lung contusion. With a velocity change of 59 km/h, this was a severe front impact collision, although the child seems to have been protected from (head) contact with the vehicle interior. Countermeasure: In a collision of this severity, no reasonable countermeasure may be possible for a child of this age in a non-integral child restraint system. It is possible that these injuries would not have occurred if the child had been seated in an integral child restraint with a five-point harness (that distributed the loads load more evenly than the three-point seat belt). Extending the use of integral child restraints beyond the ages of three or four (when children tend to ‘graduate’ to these restraints) might be a useful countermeasure for collisions such as this; however, the vehicle could also play a role. Advanced features such as seat belt pretensioners and load limiters are often not fitted to rear seats, but in some circumstances, might improve the protection afforded to children in non-integral child restraints.

C7

Booster seat; 3 year old; MAIS=2; head (skull fracture and bleeding) and abdomen injuries (liver) The child’s head injuries were likely to have resulted from head contact with the seat in front (marks were found on the “lower back edges”). The liver injury was caused by loading from the seat belt. The liver sits at the top of the abdomen, just below the ribs. Significant movement of the lap belt (and the child) would be needed to cause such an injury. It seems more likely, therefore, that this injury resulted from the diagonal part of the belt, although it would be unexpected for a child in a booster seat with a well-distributed seat belt. Measurements made inside the car by the collision investigators showed that the space in front of the child was greater than the head excursion limit in the regulation. It is possible that the booster seat was misused, with the diagonal part of the belt behind the child, or under their arm. Such misuse would increase head excursion as well as the forces on the chest. However, there was no firm evidence for such misuse in the collision report. Countermeasure: At three years of age, the child was likely to have been towards the lower limit of the size and mass specified for non-integral child restraint systems (assuming that the non-integral child restraint was being used appropriately in this case). Unfortunately no other details were available about the child. An ISOFIX integral child restraint system with a five-point harness may have reduced their head excursion and more evenly distributed the restraint forces over their chest. However, the impact conditions (including the space within the car) were within the expected performance for a booster seat with a three year old child, as assessed by UN Regulation 44.

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G8

Booster seat; 6 year old; MAIS=3; abdomen injury The conditions of this case were similar to those described in case C6, above. The child experienced an abdomen injury and a clavicle fracture as a direct result of loading from the seat belt webbing. The crash was severe, with a change of velocity (Δv) of 68 km/h. Countermeasure: No reasonable countermeasure may be possible for a child of this age in a nonintegral child restraint system. As noted above, extending the use of integral child restraints might mitigate injuries in collisions such as this, but a more advanced three-point seat belt for the rear seat might also benefit children in non-integral child restraints.

G9

Booster seat; 5 year old; MAIS=5; head, plus other injuries (lifethreatening trauma) This collision was very severe, with the child’s car experiencing a change in velocity of 94 km/h. The child received serious injuries to the head and neck, which were caused by head contact with the rear of the seat in front. The seat belt webbing loads caused a clavicle fracture, severe chest injury and multiple serious internal organ injuries to abdomen. Countermeasure: Caution is required when commenting on preventing injuries in crashes of this severity. As noted above, extending the use of integral child restraints might help, but this collision was well beyond the severity that child restraints are tested for (in both regulatory and consumer programmes). Vehicle-based countermeasures might be more feasible, such as more advanced restraints, but vehicles would also be unlikely to be tested at such a high severity.

G10

Booster cushion; 5 year old; MAIS=2; head injury (brain) The collision investigators attributed the child’s head injury to (head) contact with their own backrest. It was unclear what evidence was present for such a mechanism, although it may be plausible if the child struck a particularly rigid part of the seat, or the C-pillar. With a velocity change of 26 km/h, the severity of the collision was relatively low and within the level at which a child restraint system would be expected to perform well. Countermeasure: If the child’s injury was caused by head contact with their own (vehicle) seat, efforts to control rebound movement might provide effective countermeasures; however, vertical head excursion is already specified in UN Regulation 44 (and 129). Reducing the stiffness of vehicle interior surfaces and fittings might also be beneficial for children.

4.2


There were relatively few cases of injury to children in non-integral child restraint systems in the representative databases (at AIS≥2). Nevertheless, some trends emerged, although great care must be taken when applying these to the broader population:

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i.

The head was the most frequently injured body region in our sample, with all of the head injuries resulting from contact with the vehicle interior. This included collisions that were seemingly less severe than the front impact test in UN Regulation 44 (based on the velocity change calculated by the collision investigators) and that involved cars with ample space in front of the child. It is possible that theses child restraints were misused in a way that was impossible for the collision investigators to detect, or that the collisions were more severe than was indicated by the velocity change. The absence of cases with non-contact head injury suggests that non-integral child restraints are effective in preventing injury in such circumstances.

ii.

Injuries to the shoulder and chest were observed in severe front impacts and were caused by the forces in the three-point seat belt. Assuming that the nonintegral child restraints were used correctly, and already provided an optimum belt path, there may be limited scope for further improvement, even if the test severity was increased to match these collisions (60 – 70 km/h, velocity change). However, their injuries might have been mitigated by more advanced seat belts featuring pretensioners and load limiters. There was no intrusion and no head contacts and hence (with more advanced vehicle restraints) there might be an opportunity to prevent significant injury in collisions such as these, even taking their severity into account.

iii.

Injuries to the abdomen were observed in our sample, although their frequency was biased somewhat by one child that received three abdominal injuries in a very severe crash. There were too few cases to distinguish any trends in the type or location of abdominal injuries.

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5

Conclusions 1. The majority of front impact collisions involving children occur: below 51 km/h; with a purely longitudinal (i.e. 12 o’clock) direction of force; and with loading to both longitudinal members (particularly for serious injuries); a. It would be preferable, therefore, for the front impact test pulse in UN Regulation 129 to replicate these characteristics. b. Very few children were injured in collisions that were more severe than the test conditions in UN Regulation 129. These tended to occur without significant vehicle intrusion or structural failure of the child restraint. 2. There is very limited representative data with enough depth to identify (with any statistical confidence) needs and priorities for improving the performance of child restraint systems; a. Although child restraint systems undoubtedly perform very well in most collisions, the sparse data does not necessarily mean that the serious injury problem is small for children across the European Union; b. One of the limitations of in-depth studies is their small sample size. This means that investigations of very specific casualty populations, such as children, may not provide representative statistical data. c. Although meaningful statistical analysis could not be carried out, trends in our data suggest that the regulatory performance evaluation of child restraints should target the head, chest and abdomen (for all restraint types).

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References Kirk, A. (2012). Summary of CASPER accident database. Paper presented at Cover Child Safety Final Workshop: CASPER and EPOCh, 13-15 June 2012, Berlin. Retrieved October 17, 2012 from: http://www.biomechanics-coordination.eu/site/en/documenten.php Wismans, J., Waagmeester, K., Le Claire, M., Hynd, D., de Jager, K., Palisson, A., van Ratingen, M., and Troisseille, X. (2008). Q-dummies report: advanced child dummies and injury criteria for frontal impact. Retrieved November 8, 2012 from: http://eevc.org/publicdocs/publicdocs.htm

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Appendix A Definitions Child: 12 years of age or younger. Direction of force (PDF): The Principal Direction of Force (PDF) causing vehicle damage determined by hour sections of a clock face, positioned in a horizontal plane over the point of impact. The principal force experienced by the vehicle is split into 12 equal 30 degree “hour” sections, for example, 12 o’clock starts from 11:30 to 12:30. For frontal impacts the possible PDOFs are 10 o’clock to 2 o’clock. CDC Crush Extent:

Frontal Impacts: 

5 equal zones from front to base of windscreen



Zone 6 across windscreen



2 equal zones form top of windscreen to centre of B pillar



Zone 9 reward of B pillar

Side Impacts: 

Zone 1 to base of side glass



7 equal zones across vehicle width



Zone 9 greater than vehicle width

Rear Impacts: 

6 equal zones from rear to top of rear window



2 equal zones from top of window to B pillar centre



Zone 9 forward of B pillar

Vehicle overlap: Describes the proportion of the vehicle’s front that was impacted during the collision as a percentage. TRL

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Longitudinal loading: Describes if there was any obvious loading to the nearside (N/S) or offside (O/S) longitudinal beams of the vehicle, such as deformation or buckling. Restraint type: 

Child restraint system (CRS): the child was restrained by a device capable of accommodating a child occupant in a sitting or supine position.



Adult seat belt: the child is restrained using the adult seat belt without any CRS.



Unrestrained: the child was not restrained by a CRS, the adult seat belt or any other device.



Not known: the method used to restrain the child is unknown



Other or NFS (not further specified): an unlisted method of restraint was used or it was not further specified

Child restraint system type: 

Integral (rear-facing): a rear-facing child restraint system that features a threeor a five-point harness to restrain the child;



Integral (forward-facing) with harness: a forward-facing child restraint system that features a five-point harness to restrain the child;



Integral (forward-facing) with shield: a forward-facing child restraint system that features an ‘impact shield’ rather than a harness to restrain the child;



Non-integral with backrest: a child restraint system that raises the child’s seating position to improve the fit of the adult seat belt, and includes a backrest that supports the child – sometimes called a booster seat;



Non-integral without backrest: a child restraint system that raises the child’s seating position to improve the fit of the adult seat belt , but does not feature a backrest – sometimes called a booster cushion;



Child restraint not known: a child restraint system was used but the specific type was unknown.

Impact Severity: 

Δv (Delta-v) is the car’s change of velocity due to the impact.



EES is a measure of the energy dissipated by a crashed vehicle and may be thought of as an energy-based measure of impact severity.



ETS is a velocity, a vector quantity with magnitude and direction, unlike EES which is a scalar quantity with magnitude (speed) only. It is a measure of the energy dissipated by a crashed vehicle and takes account of the direction of the impact and any rotation about the vehicle’s centre of mass.

Injury Severity: The Abbreviated Injury Scale (AIS), 1998 Revision is used for this analysis. The AIS severity score is a consensus-derived anatomically-based system that classifies individual injuries by body region on a six point ordinal severity scale ranging from AIS 1 (minor) to AIS 6 (currently untreatable).

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AIS Score

Description

1

Minor

2

Moderate

3

Serious

4

Severe

5

Critical

6

Maximum (currently untreatable)

9

Unknown

MAIS denotes the maximum AIS score of all injuries sustained by a particular occupant. It is a single number that attempts to describe the seriousness of the injuries suffered by that occupant.

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Appendix B Sources of data B.1 GIDAS (German In-Depth Accident Study) GIDAS is a joint project of the Federal Highway Research Institute of Germany and the German Association for Research on Automobile Technique (Figure B1). It emerged in 1999 from the preceding project of the Medical School in Hanover and the University of Berlin and comprises data from the research areas Dresden and Hanover. In these two areas about 2,000 accidents are recorded each year. Each case is then encoded in the database with about 3,400 variables. Due to the facts that the research areas represent the average German topography very well, the investigation follows an exact statistical sampling plan and the number of cases is fairly high, the statistics are representative for Germany.

GIDAS - German In-Depth Accident Study

Forschungsvereinigung Automobiltechnik e.V.

Bundesanstalt für Straßenwesen Investigation at the scene Dresden und Hannover Joint Project FAT/ BASt Project start Juli 1999 Documentation of 2000 accidents each year Combined database GIDAS

Verkehrsunfallforschung an der TU Dresden GmbH

Medizinische Hochschule Hannover

Figure B1: Structure of the GIDAS project B.1.1 Weighting of the database The data for the GIDAS database is collected in a limited area and during special shift times. As a result to this controlled sample / sampling plan not all accidents that did actually happen are recorded to the database. Furthermore, there are some biases in the data. The investigation teams are not thoroughly informed about all accidents and information about injuries cannot always be obtained immediately on the spot. Sometimes, people turn out to be injured hours or few days after the accident. Thus, weighting is absolutely necessary to get a representative dataset. By attaching each case a weighting factor it is possible to match the collected data with the representative accident events using the official German statistics of traffic accidents (2011). The weighting process is done on the basis of three parameters: i.

accident severity;

ii.

accident site;

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iii.

accident type.

The accident severity is divided into accidents where people were slightly injured, seriously injured or fatally injured. In GIDAS there is a bias towards accidents with serious and fatal injuries. This bias is a result of different alarming of the investigation team by the police. The investigation team is more precisely informed about accidents with serious and fatal injuries than about accidents with slight injuries. It even happens quite often that a participant is not recognized as injured right away. The accident site is divided into accidents in urban and rural areas. In GIDAS the proportion of urban accidents is 7 per cent higher than in the German federal statistic. The accident type is divided into seven different categories. They represent the critical situation which led to the accident. Weighting the data according to the three parameters gives 42 categories (two accident sites • three accident severities • seven accident types). A weighting factor is calculated for every category. In the weighting process all accidents that are underrepresented in GIDAS (e.g. accidents in rural areas and / or with slight injuries) get a weighting factor higher than one. Over-represented accidents (e.g. fatal accidents) get a weighting factor less than one. The entire analysis is done with weighted figures. Due to the fact that the calculated weighting factors are rational numbers, the results are also provided in rational numbers. Example: If there are two real accidents with one injured child per accident and the weighting factors of these accidents are 0.645 and 0.845, the sum of weighting factors will be used in the tables (1.490). B.1.2 Description of the database This study is based on the GIDAS dataset from July 2012. Currently there are 22,347 reconstructed accidents from both investigation areas Dresden and Hanover. After weighting these accidents to the entire German accident scenario (according to the above mentioned process), 22,226 accidents have been left for further analyses. In the next step all accidents were filtered where at least one passenger car was involved. In total 1,649 children (up to 12 years) could be identified sitting in a vehicle involved in these accidents. Furthermore, a distinction was done between passenger cars manufactured from 2000 resp. 2004 onwards (Figure B2).

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Accident level

Number of weighted accidents naccident = 22 226

Vehicle level

Number of passenger cars nvehicle = 27 327

Person level

Number of children up to 12 years nchildren = 1 649

Number of children up to 12 years (Vehicles from 2000) nchildren = 530

Number of children up to 12 years (Vehicles from 2004) nchildren = 222

Figure B2: Creation process of the master dataset As defined by TRL uninjured children should also be included in the study. This will lead to a bias because in GIDAS only accidents with at least one injured person are investigated. Thus, a huge number of accidents without any personal damage but involved children in cars are not included in GIDAS. Especially the group of “MAIS0-1” is biased towards MAIS1 injured children due to missing information about the majority of MAIS0 injured persons.

B.2 CCIS (Co-operative Crash Injury Study) The CCIS project collected in-depth real world car crash data from 1983 to 2010. Injury road accidents were investigated according to a stratified sampling procedure, which favoured those where car occupants were fatally or seriously injured (as defined by the British Government definitions of fatal, serious and slight). It also favoured newer vehicles. For an accident to qualify for a CCIS investigation, it must have: i.

occurred in one of the seven defined geographical sample areas in England;

ii.

involved an injured occupant who was in a car, which was less than 7 years old at the time of the accident; and

iii.

the car must have been towed or recovered from the scene.

All car occupants who met the above criteria, and were seriously or fatally injured were prioritised and every effort made to investigate their cars and collect their injury details. A random sample of ‘slights’ within the regions was then investigated to provide a balance of different injury outcomes and crash severities. Vehicle examinations were undertaken at recovery garages several days after the collision. Car occupant injury information was collected from hospitals and coroners and questionnaires were sent to a selection of survivors who were well enough to respond. The follow-up injury data was coded using the Abbreviated Injury Scale (AIS), 1990 and 2005 editions. The AIS scale classifies injuries by their body region, type and according to a six point severity code, ranging from 1 (minor) to 6 (maximum or untreatable).

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Each casualty can be described or grouped by their Maximum AIS severity code or MAIS. Uninjured or slightly injured people are referred to as MAIS≤1or MAIS0-1 (e.g. cuts, bruises and sprains); MAIS=2 are moderately injured, for example a simple lower arm (radius or ulna) fracture or the fracture of 2-3 ribs; MAIS≥3 range from serious, to critical, to fatal injuries. The individual injuries are correlated with the vehicle damage and their causes identified. All the data captured is sanitised to remove identifying features and is stored in an anonymous database. Data gathered from June 1998 to March 2010 is used in this analysis. The representativeness of the CCIS database with regards to Great Britain’s reported road casualties is important to quantify. A brief comparison, see B.2.1, of CCIS data with a “CCIS-like” subset of Great Britain’s national road casualty database (Stats19) has indicated that the two datasets are in general agreement regarding trend directions, and there is good agreement between the occupant age distributions. There are, however, mismatches at the detailed level, and in particular in the male to female driver ratios. Some of the discrepancies may be due to the geographical bias in CCIS. However, for this analysis we have concluded that the CCIS data, when viewed by injury severity (fatal, serious and slight), is reasonably representative of accidents that involved injury to occupants, who were in cars less than 7 years old and involved in crashes in Great Britain between 1999 and 2008 (this is the period where common data was available for comparison). B.2.1 Representativeness of the database In order to give some indication of the relationship between CCIS data and the national road accident situation, as recorded in the Stats19 database, the following sections tabulate data from both databases for comparison. The stratified sampling strategy adopted by CCIS necessarily results in some major incompatibilities between the two databases. In order to reduce these as far as reasonably practicable, the national tables are based on a “CCIS-like” subset of Stats19, as follows: Accidents that occurred between 1999 and 2008 inclusive AND Occurred in England AND Did not involve a pedestrian or pedal cyclist AND Involved at least one car (Vehicle type 9) that was 7 years old or less at the time of the accident AND That car contained an occupant who was at least slightly injured. CCIS Phase 6 actually began in 1998, but changes to the Stats19 coding system introduced in 1999 make it more convenient to exclude 1998. The effect of this should be small. The restriction of the sample to England goes some small way to addressing the geographical restriction of CCIS to seven sampling areas (within England). The potential for geographical bias remains, but the restriction of Stats19 to match the CCIS areas would be onerous. The exclusion of pedestrian and pedal cyclist accidents results

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from the CCIS requirement for case vehicles to be sufficiently damaged to be towed from the scene; this effectively excludes such accidents from the CCIS sample. The inclusion in the Stats19 sample of seven-year-old cars that contained only a slightly injured occupant will not cause much of a problem, since the restriction on vehicle age to five years for this severity only applied to CCIS Phase 8, and even there it was relaxed towards the end of Phase 8. From this subset of accidents, all vehicles that were not cars (along with their occupants) were excluded. Cars that were older than 7 years or that did not contain any injured occupants were left in, provided the accident contained at least one other car that satisfied the age and severity criteria. CCIS includes car-derived vans as case vehicles but, in Stats19, many of these vehicles would be likely to be classed as Light Goods, under 3.5 tonnes (Vehicle type 19). A problem arises here because Vehicle Type 19 could also include some non-car-derived goods vehicles, and this is why the Stats19 sample has been restricted to Vehicle Type 9 (Cars). In order to match the samples as closely as possible, car-derived vans have therefore been excluded from the CCIS sample. B.2.1.1 Road Class, Casualty Class and Severity Table B1: Casualties by Road Class and Severity (CCIS & Stats19 Drivers) Road class

Fatal % CCIS

Serious %

S19

CCIS

Slight %

S19

CCIS

S19

M

8.5

10.1

8.5

7.8

9.5

8.9

A

59.6

60.5

51.1

52.3

44.5

49.9

B

16.1

13.0

17.4

14.1

16.2

12.1

C

13.2

7.5

20.7

8.9

25.5

8.3

-

9.1

-

16.9

-

20.7

2.6

-

2.4

-

4.3

-

834

6,794

3,446

67,494

8,012

926,029

Unclassified Unknown Total

Table B2: Casualties by Road Class and Severity (Stats19 & CCIS non-Drivers) Road class

CCIS

Serious %

S19

CCIS

Slight %

S19

CCIS

S19

M

11.4

9.6

8.4

9.5

10.9

10.4

A

56.8

60.3

49.1

52.3

45.3

50.2

B

14.6

12.2

19.6

13.0

15.2

11.4

C

15.7

7.8

20.8

8.2

25.2

7.7

-

10.2

-

17.1

-

20.3

1.6

-

2.1

-

3.4

-

370

3,444

1,773

33,964

4,059

442,494

Unclassified Unknown Total

TRL

Fatal %

85

CPR1801


B.2.1.2 Speed Limit, Casualty Class and Severity Table B3: Casualties by Speed Limit and Severity (CCIS & Stats19 Drivers) Speed limit

Fatal % CCIS

Serious %

S19

CCIS

S19

Slight % CCIS

S19

20

0.0

0.1

0.0

0.1

0.2

0.2

30

13.1

14.0

22.7

32.8

36.7

50.1

40

6.1

7.1

9.8

9.5

11.8

11.2

50

4.6

5.0

5.1

4.1

3.9

3.5

60

56.1

54.2

46.6

39.4

30.2

20.5

70

16.7

19.6

13.2

14.1

13.1

14.5

3.5 Total

6,794

2.7 834

67,494

4.2 3,446

926,029

8,012

Table B4: Casualties by Speed Limit and Severity (CCIS & Stats19 non-Drivers) Speed limit

Fatal % CCIS

Serious %

S19

S19

CCIS

S19

20

0.0

0.0

0.0

0.1

0.1

0.2

30

17.0

18.3

25.5

34.6

34.7

49.9

40

8.1

9.2

10.5

9.5

10.5

10.8

50

3.5

4.5

4.5

4.2

3.6

3.4

60

49.5

47.7

43.6

35.9

32.5

20.0

70

18.9

20.3

13.4

15.8

15.1

15.7

3.0 Total

TRL

CCIS

Slight %

3,444

2.5 100

33,964

86

3.4 100

442,494

100

CPR1801


B.2.1.3 Sex, Severity and Age Group for Drivers Table B5: Male Drivers by Age Group and Severity (CCIS & Stats19) Age group

Fatal % CCIS

Under 12

S19

Serious % CCIS

0.0

S19

Slight % CCIS

S19

0.0

0.0

12-15

0.0

0.2

0.0

0.2

0.0

0.1

16

0.2

0.2

0.0

0.3

0.2

0.1

17-19

9.4

10.3

9.7

9.1

9.3

7.5

20-24

14.5

14.8

14.2

14.8

15.5

13.5

25-29

10.8

10.6

13.3

11.7

11.4

12.7

30-39

16.6

16.9

19.9

20.6

20.7

24.5

40-49

12.7

12.6

16.0

15.3

13.9

17.6

50-59

12.1

10.6

10.5

11.0

11.1

11.6

60-69

9.7

8.3

6.2

7.2

6.5

6.3

70-79

7.7

8.3

5.0

5.4

4.5

3.5

80+

5.3

6.9

2.4

2.8

1.6

1.4

Unknown

1.0

0.3

2.8

1.7

5.4

1.2

620

5067

2315

42020

4936

485498

Total

Table B6: Female Drivers by Age Group and Severity (CCIS & Stats19) Age group Under 12

CCIS

S19

Serious % CCIS

S19

Slight % CCIS

S19

0

0.0

0.0

0.0

0.0

0.0

12-15

0.0

0.0

0.1

0.0

0.0

0.0

16

0.0

0.1

7.3

0.0

6.8

0.0

17-19

9.3

8.8

14.6

6.5

15.2

6.2

20-24

11.2

12.7

11.5

13.3

13.1

14.6

25-29

12.6

10.4

21.6

12.2

22.7

14.4

30-39

15.9

15.4

16.9

21.3

17.7

26.4

40-49

18.2

15.4

11.8

16.9

11.7

18.7

50-59

10.7

12.9

7.4

13.5

5.0

11.4

60-69

10.7

10.1

5.3

7.3

2.8

4.4

70-79

7.5

8.2

1.3

5.4

1.3

2.1

80+

3.3

5.8

2.1

2.2

3.6

0.7

Unknown

0.5

0.2

365

1.4

4309

1.0

214

1725

1117

25460

2959

440261

Total

TRL

Fatal %

87

CPR1801


B.2.1.4 Summary The analysis presented here is not intended to provide a robust template for scaling CCIS data to provide a national picture, but even for these modest purposes, there are fundamental difficulties in comparing the two datasets. The Stats19 database comprises all police-reported injury accidents in Britain, whereas the CCIS database is limited geographically and in terms of vehicle age, as well as being biased towards more serious accidents, both in terms of occupant injury and vehicle damage. One of the main obstacles to producing a “CCIS-like” subset of Stats19 is the CCIS requirement that vehicles should be towed from the accident scene; it is likely that a large number of vehicles in Stats19, particularly in the slight injury category, would not have been sufficiently damaged to require towing. Although it would be possible to restrict Stats19 to the CCIS geographical areas, it was beyond the scope of this analysis. The subset of Stats19 that was used for comparison was therefore as “CCIS-like” as was reasonably practicable. At the detailed level, further problems arose when comparing the datasets due to differences in, for example, the definitions of vehicle types and the categorisation of junction types. With these caveats in mind, the present analysis has found that the age distributions of the occupants in the two subsets were very similar, although there are noticeable differences in the male:female ratios in all categories of occupants. In terms of road class, the two datasets showed general similarities in the shapes of the distributions, but CCIS had a higher proportion of accidents on B roads and a smaller proportion on A roads compared to Stats19. Looking at speed limits, this situation was repeated, with general similarities between the distributions, but serious discrepancies becoming obvious on closer examination, particularly in the non-fatal injury categories. Some of the discrepancies highlighted by this brief analysis may be due to the geographical bias in CCIS, but it was not feasible to generate a geographically restricted Stats19 subset for this analysis.

TRL

88

CPR1801


Appendix C Samples characteristics C.1 Basic sample characteristics – CCIS C.1.1 Child age by restraint type Table C1 shows the age distribution for each method of restraint. The CCIS sample shows that for those children involved in injury accidents, the older the child the less likely they were to be restrained by a child restraint and more likely to have been using the car manufacturer’s seat belt (Adult seat belt). Table C1: CCIS sample – age of child by restraint type Restraint type

Total

Child age 0

1

2

3

4

5

6

7

8

9

10

11

12

N/K


116

11

24

12

21

16

5

6

7

4

5

3

1

1

0

Adult seat belt

127

0

1

1

5

7

12

10

9

14

19

18

18

11

2

16

1

0

1

1

1

0

3

1

0

1

2

2

3

0

Not known (N/K)

115

1

10

12

6

8

15

16

6

9

5

7

13

7

0

Total

374

13

35

26

33

32

32

35

23

27

30

30

34

22

2

Unrestrained

C.1.2 Child seating position by restraint type Table C2 shows the seating position of the children within the vehicle for each method of restraint. Over half of children were seated in rear outboard positions, although it is worth noting that roughly one quarter were front passengers. Table C2: CCIS sample – seating position of child by restraint type Restraint type

Total

Seating position Front passenger

Rear outboard

Rear centre

Unknown


116

20

90

3

3

Adult seat belt

127

51

55

4

17

16

3

8

3

2

Unknown

115

21

52

7

35

Total

374

95

205

17

57

Unrestrained

C.1.3 Injury severity by impact direction and seating position Table C3 shows the injury severity distribution by the impact direction and the child’s seating position. A large proportion (over 70 per cent) of the sample of children were uninjured or slightly injured (MAIS≤1). The majority of children experienced a frontal impact and were seated in the rear of the car; 21 of the 32 children with MAIS≥2 injuries fell into this category.

TRL

89

CPR1801


Table C3: CCIS sample – Injury severity group by seating position and impact direction Impact direction

Injury severity group

Seating position

Total

MAIS