The investigation of accidents and incidents in complex railway tunnel systems

The investigation of accidents and incidents in complex railway tunnel systems

Some background The Rail Accident Investigation Branch (RAIB) has investigated two fires involving freight shuttles in the Channel Tunnel 2006 2008 (joint investigation with our French equivalent BEA-TT) The BEA-TT and RAIB are currently investigating the fire that occurred on 17 January which was initiated by electrical arcing from the overhead line. This led to the stopping of the train and the subsequent destruction of two of the trucks being conveyed

Channel Tunnel freight shuttle Carrier x 16 Carrier x 16 Rear loco Loader Loader Loader Amenity coach Front loco

Fire on truck shuttle - Jan 2015

The classic investigation Immediate cause The accident Cause 1 Cause 2 Cause 3 Cause 4 Cause 1.1 Cause 1.1 Cause 2.1 Cause 3.1 Cause 3.2 Underlying factors Rescue and recovery Factors affecting consequence

What is the focus of a tunnel investigation? In the case of many complex railway tunnel systems, the initiating event (eg fire on a moving train) may only have minor consequences provided the tunnel systems operate as designed and procedures are correctly applied Tunnel investigations therefore tend to focus the ability to detect an abnormal event, and the events which follow ie. how the systems and procedures worked together to manage the consequences

A typical tunnel investigation Examination of the barriers to the initiating event occurring in the tunnel, and how they performed Causes (may be external to tunnel system) The initiating event (eg fire breaks out on train)

A typical tunnel investigation (2) The initiating event Initial detection Immediate response Protection of persons in the vicinity Protection of other trains/vehicles Evacuation to a place of safety Rescue, firefighting and recovery Damage (integrity of tunnel & safety systems) Performance of trains/vehicles Operation of tunnel systems: eg Power Lighting Telemetry Ventilation Firefighting systems Train/traffic control Application of procedures and emergency plans Human factors

Gathering key evidence Examination of the train and fire debris Survey of the damage and smoke residues Electronic data files on train train control and command systems tunnel electrical and mechanical systems CCTV communications data and voice recordings Witness evidence Social media

Understanding the sequence of events Sound investigation findings are critically dependent on a good understanding of the timeline Given the complex and dynamic nature of tunnel events, the adoption of multi-lane event sequences is often very effective

Understanding the sequence of events Time Staff actions Train Other trains Tunnel systems Smoke 08:48:37 Travelling at 120 km/h Following train in tunnel at a distance of 7.5 km Confirmed fire alarm at midpoint (flame detection) Abnormal CO levels at a distance of 1.5 km behind incident train 08:48:50 Call to following train to stop 08:48:55 All further trains prevented from entering tunnel Driver of following train applies brake Tunnel lights switched on CO levels rising at a distance of 1.5 km behind incident train

Understanding the sequence of events - Configuration of the amenity coach after completion of the controlled stop Door isolated and locked out of use VENDING MACHINES Loader Loco Door 1 VENDING MACHINES Chef de Train control panel CP 4898 France

Understanding the sequence of events - operation of cross passage doors (1)

Understanding the sequence of events - operation of cross passage doors (2)

Time Example of detailed data analysis - operation of fire detection systems Operation of tunnel based fire detection equipment in Running Tunnel North (11/09/08) 19:11:36 18:42:48 18:14:00 17:45:12 17:16:24 16:47:36 16:18:48 CO (critical) CO (dangerous) Smoke (ionisation) Smoke (optical) Flame Portal SVS shaft Crossover Fire Detection stns 14 16 18 20 22 24 26 28 30 32 34 36 15:50:00 10000 20000 30000 40000 50000 60000 Distance (m)

Example of detailed data analysis - smoke spread and the movement of trains

How to approach a tunnel investigation (1) Standard techniques of causal analysis will need to be supplemented by: 1. Comparison of actual events vs design intent how did they differ and why? 2. Systematic assessment of how safety barriers performed (identifications of failures and weaknesses). For most systems these include: prevention (eg inspection of loads) detection (eg fire/smoke detection, hot wheel detectors) initial response removal of persons to a place of safety management of other trains firefighting (people and equipment) and rescue system integrity (eg fire resistance, structural strength)

How to approach a tunnel investigation (2) 3. Assessment of the extent to which procedures were appropriate to the actual circumstances, the way they were applied, and the reasons for any non-compliance or application errors 4. Consideration of the extent to which the tunnel operator was unaware of areas of weakness in its risk control measures (i.e. areas of latent risk) safety management and the ongoing assessment of risk

Specialist areas of investigation These will include: Data analysis (related to trains, traffic control systems, electrical and mechanical systems etc) Analysis of the performance of complex electrical and mechanical systems, in particular: o o o o o rolling stock power supplies (traction and auxiliary) ventilation, smoke management and cooling systems fire detection and environmental monitoring systems pumping and firefighting systems

Specialist areas of investigation and in case of fire identification of the fire source subsequent fire growth on moving train when contained when uncontained when train stops (change of airflows relative to train) when ventilation systems are activated to aid evacuation or firefighting the effectiveness of firefighting the effect of fire on the continued operation of tunnel systems (eg overhead traction power lines) and the integrity of structures

Specialist areas of investigation - calculated rate of heat release for truck loaded with furniture (based on fire testing)

Specialist areas of investigation - modelling of fire spread

Specialist areas of investigation - understanding human performance Human performance Ergonomics Human interaction with complex control systems Human behaviour How do people react in dangerous situations and unfamiliar surroundings (as individuals and in groups)? Human physiology eg. human performance in smoke and at high temperatures

Cooperation with tunnel operators The specialist nature of investigations into accidents in major tunnels necessitates close cooperation with the tunnel s operator, who can assist with: interpretation of evidence specialist knowledge of systems, procedures etc particular insight into the challenges of operating a complex system

Investigating accidents in international tunnels (1) There have been a total of four significant fires on trains that subsequently came to a stand in the Channel Tunnel (1996, 2006, 2008 and 2015). All except the 2006 fire were the subject of international investigations The fire in the Mont Blanc tunnel in 1999 (in which 38 people died) was also the subject of an international investigation

Investigating accidents in international tunnels (2) There are three levels of legal requirements for cooperation between the: Rail Accident Investigation Branch, in the UK; and Bureau d'enquêtes sur les Accidents de Transport Terrestre (BEA-TT), in France Article 22(1) of EU Directive 2004/49/EC Binational regulations issued by the Intergovernmental Commission Respective national legislation The jointly agreed arrangements that apply when investigating an incident in the Channel Tunnel are recorded in a Memorandum of Cooperation

Principles underpinning joint investigations Mutual support and coordination Led by body in whose territory the incident train stops Free exchange of information and evidence (subject only to legal constraints attached to witness evidence) Division of workload according to investigators areas of expertise Each body meets its own expenses Jointly agreed report (drafted by lead body)

Conclusions Investigators need special knowledge and training, and to plan ahead, if they are to conduct adequate investigations of accidents in long tunnels Investigators need to identify suitable experts to provide advice in areas such as fire dynamics Investigating bodies, tunnel operators and safety regulators should work together to improve the general level of understanding of each other s needs and to promote the effective investigation of accidents and incidents