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ScienceDirect Procedia Engineering 187 (2017) 562 – 569

10th International Scientific Conference Transbaltica 2017: Transportation Science and Technology

Accident Reconstruction and Assessment of Cyclist’s Injuries Sustained in Car-to-Bicycle Collision Laurencas Raslavičiusa,*, Liudas Bazarasb, Robertas Keršysa b

a Department of Transport Engineering, Kaunas University of Technology, Lithuania Department of Orthopaedics and Traumatology, Lithuanian University of Health Sciences, Kaunas, Lithuania

Abstract Cyclists have the largest risk of severe injury when colliding with a motor vehicle. The difference in weight (mass) is huge and the collision energy is mainly absorbed by the lighter ‘object’. A cyclist simulation study captured kinematics and injuries to head, torso, pelvis and legs for one human body size, bicycle type and car model. We analysed the number of parameters, such as pelvic acceleration, Neck tension force, Neck shear force, Head injury criterion, forces acting on left and right tibia for the specific case of car-to-bicycle collision – bicyclist ride-out-residential driveway. Simulation showed that the windscreen is a frequent head and torso impact location. We found the gap in technical literature on injuries mitigated as well as on the documented effect of legislation, which until now has not been as impressive in different countries as hoped. Bridging the implementation gap between science and policy actions for the safer cycling would be a reasonable step towards decreasing the number of injured cyclists and road traffic death rates. ©2017 2017The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license © Published by Elsevier Ltd. This Peer-review under responsibility of the organizing committee of the 10th International Scientific Conference Transbaltica 2017: (http://creativecommons.org/licenses/by-nc-nd/4.0/). Transportation and Technology. Peer-review underScience responsibility of the organizing committee of the 10th International Scientific Conference Transbaltica 2017 Keywords: bicyclist ride-out-residential driveway, Neck tensile force, Nech shear force, safety, cyclist, HIC

* Corresponding author. E-mail address: [email protected]

1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 10th International Scientific Conference Transbaltica 2017

doi:10.1016/j.proeng.2017.04.415

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Laurencas Raslavičius et al. / Procedia Engineering 187 (2017) 562 – 569

1. Introduction Speed is related to crash and injury severity, – when the collision speed increases, the amount of energy that is released increases as well. Part of the energy will be ‘absorbed’ by the human body that tolerates only a limited amount of external forces. A study was carried out by researchers at the Indian University of Technology in 2006 [1], observing the dependence of a cyclist’s throwing on the collision speed and collision point. In this survey, the model of bicycle-car collision was developed by using MADYMO (MAthematical DYnamic MOdels) [2] software. Car front-bicycle side (bicyclist ride-out-residential driveway) collision was chosen for the computational study, as such situation is the most usual in cases of a cyclist’s attempt to cross the street. The starting point of calculation of the cyclist’s throwing distance was the first contact with the car, the end point of calculation – the cyclist’s secondary contact with the vehicle surface. The bicycle was moving at 10 km/h in the test and the speed of the car was ranging from 15 km/h to 65 km/h. The authors determined that the increasing speed of the car had a direct effect on the increase in the cyclist’s throwing distance. Pang et al. (2008) [3] presented the results of computational analysis obtained from the data on actual collisions involving the cyclists. The scientists had chosen three collision models for the study: cyclist-street barrier, cyclist-car, and cyclist-cyclist. An article describing the kinematics of a cyclist’s movement and results of a simulation test with the Polar-II dummy was presented at the IRCOBI conference in 2012 [4]. The study has been carried out to identify the key factors affecting cyclist’s injuries, collision speed and main injury areas. The authors linked the data entered into the software (cyclist’s posture, type of the bicycle, geometric characteristics of the car and collision speed) with the data obtained by experiment (cyclist’s kinematics after collision and his/her injuries). Several car models were developed by MADYMO software: (i) car with a short bonnet and steeper windscreen inclination angle, (ii) car with a short bonnet and larger windscreen inclination angle, (iii) car with a long bonnet and larger windscreen inclination angle, and (iv) car with a long bonnet and steeper windscreen inclination angle [4]. The Hybrid III 50th percentile male is the most widely used dummy in frontal collision tests, regardless of whether the tests are rear, full-frontal, offset, or oblique [5]. Lateral impact dummies (SID / SID HIII) are also based on Hybrid III with an adapted Thorax (that was not a subject of research) but without arms and shoulder structures [6, 7]. It should be emphasized that to account for better head-neck biofidelity, SID HIII is equipped with a Hybrid head and neck [6, 7]. Last but not least, lateral collisions between two vehicles and between vehicle and cyclist are a little bit different in their nature because, for the second case, falling cyclist strikes the car's hood with his hand and shoulder thus reducing the overall importance of head impact [7]. That is why a MADYMO model of Hybrid III dummy (but not SID/SID HIII) was selected for simulation of bicyclist ride out-residential driveway case [7]. An extensive numerical parameter study was executed to identify the most important parameters influencing injuries (Head Injury Criterion, Neck tensile force, Neck shear force, pelvic acceleration, force acting on leg) and their severity, impact speeds and main impact locations. 2. Methodology MADYMO model – a software package for the analysis of occupant safety systems in the automotive and transport industries – has been chosen for this study. We used finite element structures for the development of car-body, bicyclebody and cyclist-body (see Appendix A and Appendix B). The cyclist’s body was developed under the multibody technique: outer surfaces have been comprised of 64 ellipsoids, anthropometric attributes of a male of average composition have been ascribed to the model: average male’s weight 75.6 kg, height 1.74 m. Real model kinematics, acceleration values and values of whole body injuries have been obtained by means of computer resources. Regardless of the type of collision, the Head Injury Criterion (HIC) is the key factor defining the injuries incurred by the person. This value defines the level of injury to the person’s head. HIC value has been calculated under the following formula:

⎧⎪⎡ 1 HIC = ⎨⎢ ⎪⎩⎣ t 2 − t1

t2

∫t1

⎤ a(t )dt ⎥ ⎦

2.5

⎫

(t2 − t1 )⎪⎬max , ⎪⎭

(1)

564


a = a x2 + a 2y + a z2 ,

(2)

where a – the resultant acceleration of the center of gravity of the head in units of acceleration of gravity (g = 9.81 m/s2); t1 – the time at the initial moment of collision, ms; t2 – the duration time of the collision (t2 – t1 ≤ 15 ms). The person injured is claimed to have high chance of surviving if HIC ≤ 1000. Head Injury Criterion is considered to be one of the key criteria in assessment of vehicle safety. Head injury severity scoring is different in the medical literature than in biomechanical engineering. For a better understanding of head-on impacts severity, juxtaposition of Abbreviated Injury Scale (AIS) and HIC is presented in Fig. 1.

Fig. 1. Juxtaposition between AIS and HIC values [8].

The criteria for neck injuries for rear impact were determined using Neck tensile force and Neck shear force, expressed in kN, and the duration of these forces in ms. Maximum allowable forces have been established for these two criteria: tensile force – 3.5 kN, shearing force – 3.1 kN [9, 10]. Leg injury severity defines the level of hazardousness of the primary crash into the bumper or front edge of the bonnet. Fractures are often caused by combinations of loads and, for the Diaphysis or shaft of the main load bearing bones, like leg Tibia, these will be a combination of bending moments and axial compression. They have been characterized by Tibia Index Criterion. According to the data obtained by experiments, the maximum allowable axial load on the long bones is 10 kN [10]. The force acting on the Tibia bones may withstand the maximum of 8 kN [10]. The proposed injury tolerance limit for pelvis was 111 g [11]. 3. Results and discussion Bicyclist ride-out–residential driveway. The central axis of the bicycle has been assumed to coincide with the geometric centre of the car (see Fig. 2). This type of situation occurs when the car drives straight ahead and the cyclist comes from the right at 90 deg. angle. It can be described as the most usual situation of a traffic accident between a bicycle and a motor vehicle. According to the statistics, these situations account for up to 85% of all collisions [10]. The assumed cycling speed is 5 km/h (18 km/h). This model opens on startup; the total duration time of the developed model is 0.4 s [7]. The first contact between the car and the cyclist’s leg below the right knee is registered ~125 ms after choosing to run the model. Approx. 25 ms later the second impact has been registered: the height of the inclined bonnet top surface was such that the impact to cyclist was concentrated in the pelvis region [7]. After another ~125 ms, cyclist’s head hits the upper part of the windscreen. This kind of impact is considered to be the most life threatening injury for bicyclist ride-outresidential driveway case [7].


Fig. 2. Bicyclist ride-out-residential driveway: (a) accident causation and pre-accidental driving situation, (b) first impact (moment of collision), (c) second impact, (d) third impact [7].

Fig. 3. Factors defining the injuries incurred by the cyclist when the car speed is 40 km/h (red line), 50 km/h (blue line), and 60 km/h (green line): (a) HIC, (b) Neck tensile, (c) Neck shear (d) Acceleration values acting on the pelvis.

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Fig. 4. Factors defining the injuries incurred by the cyclist when the car speed is 40 km/h (red line), 50 km/h (blue line), and 60 km/h (green line): (e) Forces acting on the left tibia, (f) Forces acting on the right tibia.

Fig. 5. Leg injury patterns of bicyclists involved in collisions with car (Hospital of LUHS data): (a) right leg, (b) left leg.

HIC values were calculated using corresponding time intervals measured in milliseconds (Fig. 3a). For the impact speed of up 40 km/h the HIC was 805 (AIS2– moderate head injury). This HIC value means high chances of survival for the cyclist not wearing a helmet. Car speed of 50 km/h leads to increase of the Head Injury Criterion to 908, while the speed of 60 km/h raises the HIC to 1670 (AIS5) [7]. If the cyclist is being hit by a car that’s travelling at 60 km/h, his chances of surviving are minimal. Following maximum values of the Neck tensile force have been registered at different speed values of a car (Fig. 3b): 2.04 kN for 40 km/h, 2.41 kN for 50 km/h, and 2.65 kN for 60 km/h. The values of the Neck shear force vary, respectively, within the range of 0.5–1.0 kN (Fig. 3c). It has been determined that variations in the speed of the car within the range of 40 km/h to 60 km/h lead to variations in the acceleration values that act on the pelvis (see Fig. 3d) under the following pattern: 318 m/s2 (32 g), 375 m/s2 (38 g), 494 m/s2 (50 g) [7]. Fig. 4e, 4f demonstrates the forces respectively directed to the left shinbone and to the right shinbone. In view of the recommendations, the force acting on the shinbone (tibia) shall not exceed 8 kN. The graphs in Fig. 4e shown that the threshold values for the left tibia have been exceeded for all investigated speeds of the car: from 40 km/h (8.6 kN) to 60 km/h (11.7 kN). Simulation results showed that the impact load to the left leg (Fig. 4f) was in 71–76% lower than for the right leg that absorbed the direct impact [7]. We also investigated the clinical data of leg (tibia) injuries and related police reports in car-to-bicycle accidents in Lithuania [7]. Accuracy of the simulation by our model is partially evaluated by comparing them with the X-ray pictures obtained from Lithuanian University of Health Sciences LUHS (LSMU Kauno klinikos – in Lithuanian) – see Fig. 5a, 5b [7]. First, from the police office reports we identified the types of accidents that correspond to our investigation and then appealed to Hospital of LUHS for crash data retrieval and analysis [7]. The case of bicyclist


ride-out–residential driveway results in open fracture of tibia (Gustilo I, wound