Cognition, Technology & Work (2001) 3:238–252 Ownership and Copyright Springer-Verlag London Limited # 2001
Cognition Technology & Work
On the Right Track: Systematic Implementation of Ergonomics in Railway Network Control J. R. Wilson1, L. Cordiner2, S. Nichols1, L. Norton1, N. Bristol1, T. Clarke3 and S. Roberts3 1
Institute for Occupational Ergonomics, University of Nottingham, Nottingham, UK; 2Human Factors Unit, ATMDC, NATS Ltd, Bournemouth Airport, UK; 3Railtrack Operations Management, WCRM, London, UK
Abstract: At a time of change for the railway networks of Europe we have been developing tools to assess ergonomics aspects of railway network control. This is within the Railway Ergonomics Control Assessment Package (RECAP). Among the developments have been an audit instrument (REQUEST), tools to assess situation awareness (RESA) and staff loading (RELOAD), and workshops to predict opportunities for human error and organisational failure across rail network operations. This research is discussed with respect to the context of UK railway operations and the need for an expanding tradition of cognitive ergonomics fieldwork. From the findings we draw some conclusions about the roles filled by signallers, electrical controllers and zone controllers within a perspective of distributed cognitive/social networks. Keywords: Cognitive ergonomics; Control rooms; Ergonomics audit; Field study; Mental workload; Railway ergonomics; Situation awareness
1. INTRODUCTION Interest in the human factors of railway operations has never been greater, among governments, the media, the public, operating companies and academics and practitioners. Fatal accidents (and subsequent inquiries) – for instance in the UK at Southall in 1997, Ladbroke Grove (Paddington) in 1999 and at Hatfield in 2000 – have encouraged focus on safety, and on the contributions of human error, poor communications, maintenance procedures and other central issues in ergonomics (see Health and Safety Executive 2001a, 2001b). In parallel, the need around the world to shift passenger miles from the roads to rail, the increased performance of trains (especially top speeds) and the changing nature of railway ownership and organisation have encouraged focus on a systems ergonomics view of total rail network performance. This paper describes a programme of human factors research which has been carried out in order to improve understanding about the design and operation of the UK railway network. It concentrates upon control of the infrastructure (signalling, track, planning etc.) rather than upon the design or driving of trains, focusing on the responsibilities and operations of Railtrack rather than on
the whole rail industry. Safety, and in particular the recent serious accidents, is not treated explicitly but is a key aspect of the context within which we have worked. The paper opens with discussion of this context. Then the work on a Railway Ergonomics Control Assessment Package (RECAP) for a major new route development on the West Coast Main Line is summarised, and particular ergonomics studies are described. Retrospection across use of RECAP then allows us to suggest – tentatively – some fundamental descriptions of the work of signallers and controllers in the light of their situation within social and joint cognitive systems. Finally, comments are made about the place of fieldwork within cognitive ergonomics generally.
2. CONTEXT FOR RAILWAY NETWORK CONTROL Any useful ergonomics contribution must reflect its setting, and some of the current relevant context was alluded to above. Here we examine the environmental and internal factors which make the need for thorough human factors investigation into railway network control so critical, and
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which also provide the very issues, difficulties and challenges for such research. First, it has to be said that, despite recent events, the safety record of the UK railway is relatively good (e.g. Health and Safety Executive 2000). Total railway fatalities in the UK are about 40 per year, with only about 10 actually from rail accidents (this compares to over 100 deaths per year to trespassers and the same again for suicides). The most critical incidents on the railway are SPADs (signals passed at danger), with potential for catastrophic loss, but they provide about one fatal accident every two years and an average of two fatalities per year. On the basis of these figures, the Uff/Cullen inquiry report (Health and Safety Executive 2001a) says that ‘the numbers of annual fatalities from rail accidents is small – making rail travel by far the safest form of land transport’ (p. v), but that public concern justifies the high priority given to eliminating SPADs. The current organisation of the rail business has an immense effect on its operations and on human factors. In the UK for instance, over 100 companies are involved in operating and maintaining rolling stock (passenger and freight) and infrastructure. For a business that relies so heavily on good communications and integration, and one in which all parties have to share a limited twodimensional space (at times almost one-dimensional), such diffusion and dispersion of the business can create great difficulties (although the fragmentation is slowly diminishing with a number of major operators emerging through strategic alliances and buy-outs). At the same time, this distributed business offers great challenges to ergonomists. The UK rail business, and particularly Railtrack, works with a great variety of legacy systems. Even the newer IECCs (integrated electrical control centres) can appear dated alongside modern control rooms in other industries or rail network systems in other countries. Alongside IECCs there are still NX (entry–exit) panel power control systems and old lever boxes on more rural routes (see Figs 1–3). Such different generations of equipment can be found in all Railtrack operations. In addition, as with many industries, another legacy is the incorporation of original techniques or tricks of the trade (such as memory aids) into modern systems. Examples are: the token system to ensure that only one train at a time occupies single-track lines (physical tokens used to be physically transferred, and now there are radio electronic token blocks on the computer screen); much of the old physical signal and track points interlocking now handled by computer; and computerised reminder and fail-safe devices which are replicas of the equipment used when everything was purely mechanical or electromechanical. Any severe constraints on investment in transport and other infrastructure service industries will always make
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Fig. 1. IECC control centre at Liverpool Street.
Fig. 2. NX panel at Bletchley.
themselves felt in time, in terms of customer service, performance quality and reliability, as well as safety. No business has unlimited resources, and the careful identification of priorities for investment, and the total systems analysis of consequences of different investment levels, will help decision making. With the change of organisation and ownership of the business, there is a need to preserve the best of the culture within the railways, generated over many years, while recognising and modifying culture which is not appropriate to modern systems of working. As many new people join, staff should all be aware of what it means to deliver rail transport as distinct from other products (see Clarke 1998
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Fig. 3. Lever box at Stafford No. 4.
concerning safety culture under the old regime). Railway culture is highly evident in the procedures by which railways are operated (‘the Rule Book’), and in the tacit knowledge held by experienced staff, which includes their knowing which rules are vital, where there are ‘grey areas’ and even which rules are counter-productive. Cullen (Health and Safety Executive 2001b) found evidence of confusion among signallers over standing instructions (clause 12.2). Some relevant aspects of context are not a recent feature, for instance regionalisation. The UK business has long been organised into zones, areas and particular projects (such as West Coast Route Modernisation), with different applications of operating processes and procedures in each of these. Railways are also a classic example of a business that is subject to competing pressures from capacity limits, performance requirements and the need for safety; even achieving quality performance in the light of capacity constraints is a difficult equation to balance, and adding in a proactive concern for safety has proved very difficult of late. No one in the business would knowingly compromise
safety, but potential hazards created through performance decisions made elsewhere in a complex interacting system are not always apparent at the time. The rail business, like many other safety-critical industries, has to address cost– benefits of safety improvements and also any side effects from any safety measures taken, for instance delays in services elsewhere on the network. Recent arguments over the cost of safety systems hold an interesting lesson for human factors. The most sophisticated automatic train protection (ATP) was originally rejected because it was said that it would cost up to a billion pounds, meaning about £15 million per life saved, and the accepted VPF (value of a prevented fatality) for this industry was about £1.15 million. The alternative train protection warning system (TPWS) is less effective (only stopping trains up to about 75 mph although slowing faster ones) but cheaper at a total of under £500 million; therefore, it was to be implemented across the network by 2004 at the latest, with the beginning of 2003 as the company target. However, the Southall, Ladbroke Grove and Hatfield accidents may have changed all the actuarial calculations, in that – in pure probability terms – they have made death on the railway network a more likely event, purely by fact of these events having happened, and the cost per life saved for ATP has reduced considerably as a consequence, changing political perceptions. At the time of writing, the recommendation of the Uff/Cullen Inquiry into Train Protection Systems is to continue with fitting TPWS but to accelerate the fitting of the European train control system (an advanced form of ATP) on high-speed track. Interestingly, they also recommend increased human factors research as well as investigations into signals with a history of SPADs (Health and Safety Executive 2001a). The final contextual factor is the one that informs our project and this paper; that is, the changing technology and organisations in railway network control.
3. RAIL TRAFFIC CONTROL CENTRES The new west coast mainline which will be operated by Railtrack on the UK railway should be implemented in three phases: Phase 0 will see the introduction of highspeed tilting trains, Phase 1 will see line speeds raised to 125 mph and higher capacity and performance, and Phase 2 (by 2005) should see train speeds raised again to 140 mph and the implementation of ATP. A number of new train control systems (TCS) will be implemented, although at ERTMS (European rail traffic management system) levels 1 and 2, rather than 3 (Traverso 2000; UIC 1998), as will electrical control via SCADA (supervisory control and data acquisition). Of greatest interest to the current work on human factors will be the introduction of west coast rail traffic control centres. These will mean that future control
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Fig. 4. Ideas for the new rail traffic control centres (Source: Railtrack and Bennetts Associates).
of the railway network is much more centralised, with many of the functions and operations currently carried out at numerous small and large sites distributed across the west
coast mainline being brought into fewer larger centres. The integrated functions will include zone control, electrical control, signalling and possibly representatives from the
Table 1. Edited versions of network management scenario descriptions Signalling perspective Bill, the signalling controller, started work at the Euston signalling control room at 8 a.m. and it is now 8.30 a.m. He works with a team of about four people and he is not especially busy at the moment because everything is running smoothly. If everything continues like this, his workload will go down after the peak around 9.30 a.m. A train with headcode 4H38 is just about to leave the station and run over his section of track. (This headcode identifies it as a passenger train travelling from Euston to Willesden.) He is now mentally planning the route that the train will take through his section towards Willesden. He does this by scanning the route ahead to make sure everything is clear on his section of track, using his on-the-job knowledge of the route, and glancing at the simplifier on the clipboard to confirm the train times through his section. At the moment, his section of track is clear so he sets the path that the train will take out of the station. During this task his main focus is on ensuring safety and making sure that this train meets the timetable. Electrical control perspective Fred, the electrical controller, has just finished breakfast with the night controller in the electrical control room at Willesden. The night controller passed him a photocopy of last night’s log and pointed out that some emergency engineering work scheduled for last night didn’t get completed. They also talked through the routine maintenance and testing scheduled for the day and discussed the fact that their jobs will be moving to Rugby in 24 months. Fred’s main concern is ensuring the safety of the line. As this is the rush hour, he is keeping an eye out for power blips that could cause disruption to the network. He knows that around this time the TOC sends out a train that regularly trips the line. Fred deals with a number of signal boxes within his area of electrical control (at 200 track miles, this area is about four times the size of the signalling control areas). He uses the schematic electrification charts to help him manage the feeders, breakers, substations and track circuits but he also uses his internal on-site geographical knowledge of local features (such as gantries) to manage the network. Zone control perspective George works in one of the seven UK zone control rooms. His Birmingham-based control room is responsible for a large number of signal boxes. George is the area route controller for Euston and works with five other controllers. He worked his way up through the signalling grades, unlike some of the newer lads. Recently he has thought about moving to EWS where he can earn more money for doing less work. George’s goal is to optimise the performance of his area taking account of what else is happening in the zone. This may involve overall service issues but rarely includes regulating individual trains. His main role is to take an overview of the system by combining disparate sources of information. George reviews TOPS, TRUST and the SIVS screens to familiarise himself with the current status of the network in his area. He talks to signallers, controllers on impinging zones, ECROs, MOMs, IMCs, local authorities, utilities, highways authorities, emergency services, NCC and the Met Office. He uses data from Railtrack’s outlying weather stations to anticipate problems. He uses all of this information to build a zone-wide picture so that his area can respond appropriately to emerging events, such as a bridge strike. He records what happens in his area and co-ordinates Railtrack’s response when things go wrong. George came on shift around 7 a.m. and received a briefing from the night controller for his area. As soon as he sits down with his first cup of coffee, his phone rings. George is constantly occupied in his job, either dealing with problems or (as now) maintaining the delay attribution system until his assistant arrives for work at around 8.30.
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train operating companies. There will be opportunity for new display and communications systems, particularly to support operations under ERTMS, to reflect the increased information that the driver will have in-cab (see Fig. 4). Critically, as a consequence of the integration of functions and the new technical systems, there will be changes in the nature of the roles and organisation of work for staff in the control centres. In order to gain an appreciation of the different roles of staff hitherto largely separated (functionally and geographically), the scenario descriptions in the panels of Table 1 were produced during structured workshops with representative signallers, zone controllers and electrical control room operators (ERCOs) who had been seconded to the operational concepts team. Some of these representatives were later also involved in scenario development and potential error assessment workshops (see later in the paper). Descriptions such as those in Table 1 were produced to illustrate the roles of people who would now be working much more closely together than before on most of the network, and which might be filled, in some visions of the future, by the same staff. Early on in the west coast route modernisation (WCRM) project, the Operational Concept Team made a commitment to the early and continuing incorporation of human factors considerations throughout the development process. The commitment was to human factors in its widest sense, embracing the notion of railway network control as a complex interacting socio-technical system and the need to account for physical, cognitive and organisational ergonomics throughout the development of the control centres. The human factors strategy which was set by Railtrack defined the operators and maintainers as being
at the heart of the system, emphasised the importance of user-centred and user-led design, and took an integrated view of human factors. In order to deliver an operational ergonomics programme, structured, robust and systematic methods for analysis, design and evaluation were required.
4. RAILWAY ERGONOMICS CONTROL ASSESSMENT PACKAGE (RECAP) A number of different studies and initiatives have been brought together in the human factors programme applied to the future rail traffic control centres. The various components of this programme are shown in Fig. 5; the methods and early findings of the main element, RECAP, are described in the sections that follow. All other elements are described in the discussion on next steps later. A fuller description of the development of RECAP can be found in Cordiner et al (2002). The initial brief for the research was to produce a human factors measurement package with three components: (1) provide human factors audit of current rail network control systems; (2) allow early development of evaluation criteria for prototypes and final versions of new systems, including the control centres; (3) at the same time, feed design intelligence into development of the new technical and organisational systems. To meet these three different, if interconnected, requirements, ‘assessment’ has been handled in a variety of ways. In part, ergonomics assessment needs will be met through development of audit tools, largely questionnaires or rating scales, but also direct observation protocols, through running workshops and discussion groups with salient staff and through a series of one-off field investigations. The central part of the work –
Fig. 5. Components of the work on railway ergonomics evaluation.
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RECAP – has contained three particular sets of tools (REQUEST, RELOAD and RESA). In the next phase of work, modules which have been developed from concurrent work on the human machine interface, team working, organisational and safety culture and decision making and information handling will be incorporated into REQUEST. REQUEST has been applied across a range of Railtrack staff, mainly signallers, zone controllers and ECROs, but also some supervisors and managers. RELOAD, in its various forms, has been carried out with signallers. RESA has been applied to both signallers and ECROs. 4.1. Railway Ergonomics Questionnaire The first and central tool within RECAP is REQUEST (the railway ergonomics questionnaire). This has been designed as an audit which can be delivered on a periodic basis (for instance, annually or biennially), or can be run especially under particular circumstances, such as systems change. Initially we produced a framework which defined 13 critical human factors areas which it was anticipated would be
affected during the system change. A rationale for the selection of the factors can be found in Cordiner and Wilson (1999) and Cordiner et al (2002). Extensive review of the control room ergonomics literature was undertaken to identify if any suitable measurement methods could be adapted from other industries or could be extracted from relevant ergonomics guidelines (e.g. Kinkade and Anderson 1984; NOREG-0700, 1996). At the same time a search for existing performance measurement methods already used in Railtrack was undertaken. A matrix of candidate measurement methods, conditions of measurement, the human factors aspects to be considered and the possible sources of information was then produced. This was reviewed by the operational concept design team from Railtrack, where the various methods were evaluated for their practicality, appropriateness and anticipated acceptance in the field (see Cordiner et al 2000). REQUEST has now been delivered and analysed in 1998 and 1999, with 90 (36%) returns from 247 delivered to 11 sites in 1998 and 156 (46%) from 342 delivered to 15 sites in 1999. It is currently being prepared for delivery
Table 2. Scales administered over three years within REQUEST Area of measurement Scales used Personal details Workplace Health and safety Job and work design
Teams
Stress Activity level Communication Decision making Human–machine interface
Safety culture
Number of Items in each year
N/A Workstation ergonomics Work environment Pain/discomfort General well-being Satisfaction Job complexity Control – timing – method Monitoring demand Repetitiveness Problem solving demand Responsibility Skill utilisation Social interaction Support Communication Cohesiveness Trust Occupational stress Percentage of time Communication links Responsibility perceptions Clarity Helpfulness Ease of use Transparency Learning Management proactivity Helpfulness Ease of use Transparency Learning
1998
1999
2001
11 15 10 9 12 16 8 5 3 4 3 6 4 4 3 5 4 4 6 37 12 12 12 – – – – – – – – – –
11 15 10 9 12 15 8 5 2 3 3 5 4 4 2 5 3 4 6 34 – – – – – – – – – – – – –
11 15 10 9 12 15 8 5 2 3 3 5 4 4 2 5 3 4 6 34 – 3 2 4 5 4 3 3 5 7 3 5 2
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Fig. 6. Examples of questions from some REQUEST scales.
in 2001 (the events at Ladbroke Grove and Hatfield and consequent disruption meant that the intended 2000 delivery was postponed). Results across all applications will be reported in Norton et al (in preparation). REQUEST is being run as a rolling survey in two senses. First, a number of sites will be retained in the sample in consecutive years and some will be replaced year on year. Second, several of the scales of measurement will be retained in the questionnaire each year (albeit with minor modifications early on, to improve ease of completion, validity and meaningfulness); some scales will be utilised only on some applications, and others will be added as required by organisational or technical developments, or for particular site assessments. Table 2 summarises the scales used in the three versions of REQUEST. Examples of items are shown in Fig. 6. The scales concerning perceptions of, and attitudes to, the workplace and the work environment have been developed from previous work at the Institute for Occupational Ergonomics with a number of companies, and have been changed only slightly to be appropriate for this particular context. Health and safety is assessed through the body part discomfort assessment technique of Corlett (1981) and selected items from the Health and Wellbeing Questionnaire of Cox et al (1983). Perceptions of sources of occupational stress are measured through appropriate adaptation of Cooper et al’s (1988) Occupa-
tional Stress Indicator. For work organisation, assessment is through the Job Satisfaction scale of Mullarkey et al (1999) and scales to measure job characteristics such as complexity, control and demands adapted from those used previously by one of the authors (JW) in manufacturing industry (e.g. Watson and Taylor 1995). Scales to assess team support, interaction, trust and cohesiveness are from the same sources with additional items based on Wilson and Whittington (2001) and the work of Salas and colleagues (e.g. Brannick et al 1997). The assessment of information flows, communication sources, time per activity and decision making was carried out through of a variety of questions such as shown in Fig. 7, during 1998. Because of the extra time and effort required to complete these questions they were withdrawn in 1999, but are subject to retesting in various formats during 2001. The scales are based on ones used in manufacturing systems (e.g. Mullarkey et al 1997) and planning and scheduling (Crawford et al 1999). Examples of the types of the descriptive analysis possible are shown in Fig. 8. For decision making in particular, and to a lesser extent communication sources, the importance is to highlight gaps or inconsistencies in understanding, and the graphical form of reporting results does this very well. For some of the adapted scales, population norms and reliability data were available and factor analyses had previously been performed to allocate questionnaire items
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Fig. 7. Examples of communication and decision making questions from REQUEST.
into appropriate categories. For the new scales these data were not available; therefore question items were initially allocated to subscales after formal and structured discussion of the items by experienced ergonomists. After sufficient data had been obtained, factor and reliability analyses were performed and the resulting item groups or scales named (Nichols et al 1999). 4.2. RELOAD: Railway Ergonomics Workload and Staff Loading One of the major decisions in the organisation of operations for the new control centres will be of how many staff will be required. Remember that these centres will bring together at one site a large number of personnel from different functions (possibly including signalling, zone
control, electrical control) who used to work in separate offices and whose work was duplicated at several sites up and down the west coast route. Moreover, the new technical systems are as yet unspecified and so the degree and balance of system monitoring and control – the allocation of function across the distributed cognition network – cannot be determined. Therefore, projections of the workload for control centre teams in the future, and consequently the size of these teams, is not going to be an easy task, but is vital as identified in the Cullen Inquiry Report into Ladbroke Grove (Health and Safety Executive 2001b, clauses 12.20–12.23). The human factors literature does not offer great assistance in determining best crew or team sizes. There is some new and largely unpublished work in the military, such as a Complement Generation Validation Tool from
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Fig. 8. Examples of communication and decision-making data representation. (a) Points failure: information. (b) Broken rail: decision making.
Thales Human Factors and CREWII from the UK Ministry of Defence (Wotton 2001; Bost et al 1998; see also Lee 1997 for a simulation model). Brabazon and Conlin (2001) have developed task analytic and checklist tools in a ‘physical assessment’ and a ‘ladder assessment’ to assure that planned staff numbers will cope with normal, abnormal and emergency scenarios. With particular reference to rail, Cowell (1998) has examined the related area of fatigue for safety-critical staff. The North Staffs project team within Railtrack is currently attempting to predict workload using chunking and recombining task elements from task analyses. The closest to a directly useful contribution has been reported by Reid et al (2000), in which they attempted to predict railway signaller workload with technical systems change (NX to VDU with automatic route setting) by using task analysis and the NASA TLX workload assessment tool (see later) on simulator trials.
In our work we have taken a field-based approach to the investigation of workload and staff loading (see Nichols et al 2001). This has been done to reflect both the workload perceived by signallers and controllers, and also to try to measure levels of task loading, in terms of the entities or variables for which staff are responsible, their behaviour and their span of control. Eventually information will be gathered on individual and team capabilities. In addition to some measurement of experienced workload over time within the REQUEST audit tool, the RELOAD package is a field observation-based method of assessing the loading on individuals and teams. In the work carried out so far, we have been chiefly concerned with defining methods, measures and metrics which will allow understanding of staff loading into the future. The subjective workload assessment carried out is not strictly related to what task load people can or should undertake, but is used for
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examining the relationship between perceived loading and data from field observations. We have explored a number ofdifferent ways to record subjective experience of workload. Early trials with the NASA-TLX (Hart and Staveland 1988) identified a number of problems, related to the fact that the tasks that we are assessing are not discrete or easily bounded, the terminology of TLX is a little obscure for our participant groups, and the time taken to respond to the scales is unacceptable in field studies. Therefore we carried out the first full study with respondents rating their overall workload from time to time using the adapted form of the US Air Force Flight Test Center (AFFTC) seven-point scale (Ames and George 1993). This asks for a single rating of workload combining perceived demands from activity level, the system, time and safety concerns (see O’Brien and Charlton 1996, p. 194), although we did revise the wording slightly to be appropriate for the railways. Participants were familiarised with descriptions of the four elements at the outset of their shift, and it has proven useful for immediate and regular field measurement. We are aware of the assumptions and dangers of using such a unidimensional measure of workload, albeit with its advantage of concurrency, and so in addition we have employed retrospective rating of the perceived load within 10 minutes of a particular activity finishing. For this we have employed three subscales – ‘planning and deciding’, ‘time available’ and ‘physically tired’ – taken as appropriate from the NASA TLX. Beyond this, considerable time spent with signallers in particular revealed boredom, lack of attention and being ‘out of the loop’ as increasingly serious potential problems as technologies change. Therefore, we are currently in the process of developing a measure of work underload, using the technique of paired comparisons to develop a scale which will include items for ‘under-challenged’, ‘disinterested’, ‘bored’, ‘difficult to concentrate’ etc. (Bristol and Nichols 2001). This may be incorporated into REQUEST in future, or used for concurrent workload rating in the RELOAD package. In order to begin to make predictions about future staff requirements it is necessary first to examine how many people are needed to carry out all the current rail network control tasks, and the load undertaken by each operator. To do this it was necessary first to define the elements of task load. While it was recognised that the loading on operators is more than the sum of the tasks they are responsible for, it seemed that such a task or activity measure might establish a useful first benchmark. The critical measures as regards task loading in the workplace were divided into static load and dynamic load. Examples of the former are the number of lines, points, signals, track circuits and level crossings under the control of an individual during their shift. Examples of dynamic loading are the train movements handled per hour, the
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pattern of these movements and current possessions (usually maintenance activities) being handled. Measurement was carried out by an experienced ergonomist and an experienced member of railway staff, approximately every 10 or 20 minutes during a shift. The static and dynamic load measures recorded have then been related to subsequent analysis of video-recorded activities (using the Observer VideoPro analysis system) and the workload selfreport ratings. Tasks observed include setting routes, using phone or radio, operating CCTV and talking to colleagues. Link analyses were also carried out for all communications tasks. The data constitute a first start in assessing numbers of people required in the new centralised control centres. The underlying thrust of this approach is to assess workload through several different but compatible methods, in order to build up a reliable picture of staff loading, and the influences on this, in practice. 4.3. RESA: Railway Ergonomics Situation Awareness The third main part of RECAP is RESA. The notion of situation awareness (SA), developed for understanding of pilot performance in the cockpit, appears to have great resonance for the railway engineers and operations teams with whom we are working. The definition we developed of SA for railway signalling – ‘a signaller’s perception, understanding and anticipation of static relations and dynamic interactions within and between the infrastructure, trains and other affected vehicles in the section (panel) under his or her management’ (Wilson et al, 1999) – was agreed by operations staff to reflect well the nature of signallers’ skilled performance, at least in part. We carried out some early measurement of situation awareness in a rail control simulator, using the method of simulator freeze to assess level 1 (observation), level 2 (understanding) and level 3 (projection) situation awareness (Endsley 1995a). However, within the context of RECAP, our real requirement is for a robust measure of situation awareness that can be used in the field. For this purpose we adapted work of Laura Donohoe and colleagues at the Human Factors Group of the UK National Air Transport Services, itself based around the Situation Awareness Global Assessment Tool (SAGAT) of Endsley (1995b), and also used in other control room work (e.g. Collier and Folles 1995). It is impossible – for safety and operational reasons – to replicate in the field the freeze of the screen when using SAGAT in simulators. Instead, we arranged for each signaller under study to hand over their role to a colleague for a short period, about every 20 minutes. Then two or three questions were asked from a set of 24, using graphical aids to support signallers’ answers; these questions related to both ‘static’ and ‘dynamic’ aspects of work, and particularly with respect to information displays, and referred to any of
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Fig. 9. Examples of questions used in RESA.
the three levels of situation awareness. A validity check on the responses was made by a ‘reference signaller’ who worked with us in the field. A sample of the questions asked is shown in Fig. 9 and an example of the graphical response
recording diagram is shown in Fig. 10. The questions were generated by starting with a goal-directed task analysis (reviewed and approved by signallers and managers), which was transformed into a goal hierarchy and in turn into an
Fig. 10. Example of a RESA graphical response recording diagram. (Note: two elements deliberately blurred)
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SA information requirement stratification on which the questions were based (see Endsley and Rodgers 1994). The method has only been trialled with four signallers but we believe that we are finding explainable differences in levels of situation awareness between individual signallers and between different control stations (Wilson et al 1999). For instance, the percentage accuracy scores for the four signallers studied were 63%, 92%, 75% and 83% (the first signaller used an early version of the RESA tool which was not as clear on the diagrams). Of the others, the one scoring 92% was, in independent discussions with the manager, said to have the best ‘awareness’ of the job out of the whole crew. Despite practical difficulties of SA measurement in the field and theoretical doubts (e.g. see Flach 1995), we will continue with this line of investigation.
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comparison with other studies and domains. Current HCI rating scales are not entirely suitable for control rooms generally and railway network control in particular. We have drawn upon such scales, control room ergonomics generally and our own railway research to develop new scales; examples are shown in Fig. 11. Additional scales are being developed in order to assess perceptions of company, work and safety culture. Given the critical balance between capacity, performance and safety that has to be made in industries like railways, some of the questions on culture are addressing related perceptions (Fig. 12). Recent accidents and the inherent nature of the railway business mean that the understanding of opportunities for human error and organisational failure, and analysis of near-miss and other incident reports, have taken on a new importance. Within the overall railway network control
5. FURTHER DEVELOPMENTS IN RECAP The REQUEST tool has now been run and analysed twice across 11 and 15 sites in 1998 and 1999, and is currently being run again across 30 sites in 2001. Comparative results across these first three years of application are in preparation (Norton et al in preparation). RESA was piloted in 1999 and RELOAD has been under continual development during the period since 1998. In the first administration of REQUEST, we included scales to assess perceptions of information flows and decision-making responsibility during certain critical events. For these questions, respondents are asked to what extent a number of other job functions (usually between 6 and 10) are responsible for decision making in certain situations or scenarios, and to what extent they transfer information to and from these other job functions in the same situation. About 10 scenarios have been used. The output of this method is a profile in which differences between staff functions in their perception or understanding of decisionmaking authority and information handling are quite easily seen graphically. In the first administration of REQUEST, running these scales proved to make the instrument too long, and required too much time for filling in. Therefore this has become a separate package and the scales and measurement method are being refined, although a small subset of these questions will be included in subsequent administrations of REQUEST. One very early requirement for annual audit was assessment of the information interfaces with which signallers and controllers work. We have delayed incorporating such assessment into the REQUEST instrument while trying to develop items and scales which would be meaningful across the range and variety of information systems used in railway network control (including a large number of legacy systems), and which also would allow
Fig. 11. Examples of new interface items for REQUEST (all rated from strongly agree to strongly disagree).
Fig. 12. Examples of new culture items for REQUEST (all rated strongly agree to strongly disagree).
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ergonomics evaluation programme we are addressing the issue of error from two different perspectives. First there is an ongoing study of safety-critical communications within network control, and particularly within possessions (i.e. possession of the line by maintenance or other functions). In this work a tool has been developed – RCAT – to allow retrospective assessment of a variety of different types of incident reports and also to allow collection of data on any event occurring at the time (this work is reported by Murphy 2001). In parallel we have developed the Railway Ergonomics Predicted Error Analysis Tool (REPEAT). This supports mixed groups of railway staff and ergonomists in walkthrough of various operational scenarios. For each stage of these scenarios the potential safety or performance problems are identified, together with the degree of hazard associated with this, the likely consequences and any route to rectification. The extent to which human error or organisational failure may be involved, and the factors underpinning this, is also discussed and documented. The information from the use of REPEAT will be of interest in itself in designing operations for the new rail traffic control centres (RTCCs), but will also feed into both the study of safety-critical communications and the development of early concept designs for the new information displays.
6. ROLES WITHIN SOCIAL AND COGNITIVE JOINT SYSTEMS It is impossible to generalise too much about the work of those we have studied. Not only do signallers, zone controllers and ECROs have very different functions, but they also have different perspectives and cultures. Moreover, the work of signallers, especially, is very different depending upon the size of the unit, the degree of integration with zone control and the technology used (particularly whether VDU or NX panel). But since one development in future may be the coming together of different signalling and control functions in the RTCCs, it will be useful if we can describe the jobs and teamwork needed in control of networks like the railway system in order to support general decisions about staffing. We can make some tentative suggestions about cognitive and social roles, largely based on related research. First, we can certainly say that network operators of today, and even more tomorrow, are actors in a system of distributed cognition. As well as the signallers and controllers and their own computer systems acting as Hollnagel’s (1997, 2002) joint cognitive systems, the thinking and decision making will be distributed more widely, across the staff, the trackside and signalling systems, the driver, new in-cab information systems, TOCs and IMCs (train operations companies and infrastructure maintenance companies) etc.
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Second, the operators certainly work in a social setting. In this, their peripheral awareness (Mackay 2000, in the context of air traffic controllers) of what else is happening in the control centre, and mutual awareness (Artman and Waern 1999, in the context of an emergency coordination centre) of tasks or difficulties faced by their colleagues, will become increasingly important. On the whole, scheduling of the railway – whether in long-term, short-term or very short-term planning – is carried out by specialist staff (the subject of a separate study we are carrying out). Some of the short-term planning – and certainly some of the rejigging of train movements to cope with problems such as poor weather, infrastructure failure or train breakdowns – is presently handled by zone controllers and signallers working in conjunction. This will happen more as a team activity in the RTCCs, when the responsibilities of planners and even those of the operating companies may be brought within the same ambit. Therefore, operators now show evidence of filling the hub and filter role for formally handling information and the link and net role for interpersonal informal networks, and in future may need to fill the balance and value role as decision makers (all roles as proposed by Crawford et al in preparation, in a model of schedulers). Two other roles must be considered as regards cognitive activity in rail network control. The Rulebook provides the rail industry with an operations framework. This huge collection of procedures and standard operating practices is referred to whenever staff are asked ‘What would you do if?’ or ‘What would happen when?’ No doubt, staff work outside the Rulebook if situations dictate that they use their tacit knowledge, judgement and experience, especially if they have to act fast, but we believe this happens rarely, one reason being that the railway network and its operations have grown slowly over many years and so almost every situation that could present itself has been covered in the rules or in amendments to them. Thus staff at the moment are not testers of systems as were some of Mackay’s (2000) more experienced air traffic controllers; on the other hand, the complexity of the rules and the knowledge and experience to know what aspects are relevant means that their job, especially in the NX panel boxes, cannot merely be seen as routine and rule-based. Perhaps they can be described as knowledgeable rule followers or as rule sifters. Importantly, as new systems such as ERTMS, ATP and TCS are implemented, the rapid change in operations may make much of the Rulebook less relevant and give rise to a new role of intelligent decision makers. Finally, the critical part that the functions of signals, zone control and electrical control will play in meeting the demand/capacity/performance/safety balance referred to earlier, given the obvious limitations on capacity, will increase with the RTCCs. In this role they are a demand manager. Increased passenger and freight traffic, a high-
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speed inter-city route sharing infrastructure with crosscountry trains, a mix of 140 mph passenger trains and slower freight trains – including those relying on in-cab signalling and those relying on trackside signalling – will place great reliance on a workforce in the control centres who can manage these demands while fulfilling all the other roles highlighted in this last section. The understanding that is being provided by the RECAP and related activities will assist greatly in ensuring the best combination of human skills and technical systems is in place for the next generation of railway control. Jobs in these systems will be different but no less challenging.
7. COGNITIVE ERGONOMICS IN REAL CONTEXTS This paper has described, in summarised form, an ongoing programme of human factors work to support the design of railway network control in the future, particularly the methods being employed. The programme of research has consisted of a number of threads which are interlinked but also are running somewhat independently. The consistent theme across all this work is that it is being carried out in the field, not in as great detail and focus as use of true ethnomethodology (the sheer number of sites and personnel investigated would have precluded that), but nonetheless carefully and with slow piecing together and traceability of evidence. There is a great need for cognitive ergonomics to better establish its approaches and methods for use in real-world contexts. There has long been an argument about the crucial nature of context and the limited understanding that can be gained from laboratory work in ergonomics. This is particularly important when studying the joint cognitive and social performance that is required in modern organisations, where the work is rich and varied and networks and supply chains are the normal way of operating; in these domains methods of study need to be compatible with the ideas which underpin distributed cognition. However, to date, cognitive ergonomics has been relatively poor in its fieldwork. This is not to say that some excellent work has not been carried out. But, only a small minority of studies have been conducted in the field as compared to laboratory experiments or theoretical modelling work; few methods outside those of (cognitive) task analysis have been applied; and much of what has been carried out has been in contexts such as the military or nuclear power plants, where it could be argued that work is very similar to tasks carried out in controlled conditions in simulators. This research into railway ergonomics is providing a platform for further development of a cognitive ergonomics field methodology. The need to examine such distributed networks in the rail industry is now recognised at official levels: ‘I also agree that signallers should be
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encouraged not to view SPADs as a driver problem, but to see themselves and the system with which they work as part of a defence against a SPAD developing’ (Cullen Inquiry, Health and Safety Executive 2001b). The programme to investigate the ergonomics of rail network control has three practical outputs: (1) audits of current systems and operations; (2) benchmarks against which to assess changes in the human factors of the future RTCCs (at first on the west coast route, subsequently elsewhere); (3) information to feed into the design of technical and organisation systems for the RTCCs. In addition the researchers have the aim of better understanding the work – the tasks, roles, support, settings, constraints and consequences – of those who ensure that the rail network runs efficiently and safely. Acknowledgements A number of our colleagues have contributed to the work reported here. At Nottingham this has included Kristian Hammar, Wendy Morris, Philippa Murphy and Claire Whittington. At Railtrack, knowledge has been provided by Phil Frazer, Roger Heathfield, Bob Muffett and John Robinson. To all of them we owe a huge debt of gratitude for their effort and insight. References Ames LL, George EJ (1993). Revision and verification of a seven-point workload estimate scale. Technical Information Manual. Air Force Slight Test Center, Edwards Air Force Base, CA. Artman H, Waern Y (1999). Distributed cognition in an emergency coordination centre. Cognition, Technology and Work 1:237–246. Bost JR, McKneely JAB, Hamburger T (1998). Surface combatants of the future: reduced crew warships. In Proceedings of the Human Factors and Ergonomics Society 42nd annual meeting. Brabazon PG, Conlin H (2001). Assessing the safety of staffing arrangements for process operations in the chemical and allied industries. HSE contract research report 348/2001. HSE Books, HMSO, Norwich, UK. Bristol N, Nichols S (2001). Impact of new technology on operator workload: development of a measure of underload. In Hanson MA (ed). Contemporary ergonomics 2001. Taylor & Francis, London, pp 251– 256. Brannick MT, Salas E, Prince C (eds) (1997). Team performance assessment and measurement: theory, methods, and applications. Erlbaum, Hillsdale, NJ. Clarke S. (1998). Safety culture in the UK railway network. Work and Stress 12:285–292. Collier SG, Folles K (1995). SACRI: a measure of situation awareness for nuclear power plant control rooms. In D. Garland and M. Endsley (eds): Proceedings of the international conference on experimental analysis and measurement of situation awareness. Daytona Beach, FL, EmbreyRiddle Aeronautical University Press, Daytona Beach Florida, pp 115– 121. Cooper CL, Sloan SJ, Williams S (1988). Occupational stress indicator: management guide. NFER-Nelson, Windsor, UK. Cordiner L, Wilson JR (1999). Evaluation of control room human factors: a case study in the railway industry. In Proceedings of people in control conference, 21–23 June 1999, Bath, UK, pp 26–31. Cordiner LA, Nichols S, Wilson JR (2002). Development of a railway
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