The burning desire to prevent fire catastrophes

Fire incidents in trains can be divided into two main groups: those we can manage and those we cannot. For example, if a burning train comes to a stop inside a tunnel, the situation may become very difficult to manage, both for the tunnel operators and fire services. Such scenarios are fortunately rare. Statistics show that the risk of a large fire incident in a train is low. The risk is even lower of such an incident in a tunnel. This is a fact that many involved in the safety issues of trains and underground subway systems are very well aware of.

Despite the risk of fire incidents in tunnels being very low, there have been occasions when fires have developed into catastrophic events and these few disastrous fires have placed a focus on fire safety in rail and subway tunnels. When such incidents occur, the media focus becomes extremely high and the work of safety authorities and tunnel operators comes under close scrutiny. The agenda is set by these incidents but it does not necessarily mean that the safety standards are ruled by them.

Real incidents

The most severe incidents have been found to happen in underground subway systems. The main reason is the high number of passengers in the system and the fact that the subway trains obviously run largely in tunnels. Examples of such catastrophic fires are the Baku incident of Azerbaijan in 1995 which left 289 dead and the Daegu incident of South Korea in 2003 leaving 198 dead. In both cases, people became trapped in toxic smoke and heat and had difficulty escaping from the subway coaches and underground system. In both cases a number of subway coaches were totally burned out. The reasons and circumstances for these fires differ. In Baku, the fire started under one of the subway coaches whereas the incident in Daegu was caused by arson. Underground subway systems are extremely vulnerable if a fire is able to develop as they may contain many passengers and they are often complex in their structure. The fire services face enormous problems when fighting and rescuing passengers from these systems. There is a tendency to over rate the capacity of the fire services to rescue people trapped in such fires.

In railway tunnels, there have been four accidents reported with over 150 people dead since 1921. In 1921, a fire occurred after the collision of two trains in the Batignolles tunnel in France, resulting in 28 deaths. In 1971, a locomotive fire occurred in the Wranduk tunnel in former Yugoslavia, resulting in 34 deaths. In 1972, a fire occurred in a restaurant coach in the Hokuriku tunnel in Japan which resulted in 30 deaths. In 1998, gas canisters exploded in the Gueizhou tunnel in China, resulting in over 80 deaths.

In recent years, numerous fires of freight trains in tunnels have occurred. Examples include:

• The Summit fire in the UK, 1984
• Eurotunnel, UK-France, 1996
• The Exilles tunnel in Italy, 1997
• Leinebusch tunnel in Germany, 1999
• The Baltimore Howard Street tunnel in the USA, 2001

These fires burned over a long period of time with numerous freight wagons involved. The fire services had great difficulties in fighting these fires. There are also examples of more exceptional train fires; such as the one in Kaprun, Austria in 2001. In this incident, a funicular train burned inside a tunnel that had an extremely high slope and despite a very low fire load the tunnel turned into a chimney, resulting in the death of 155 people.

There are however many examples of fires that started but did not develop into catastrophic infernos. The fire started in a Swedish locomotive and spread to the rubber belly connecting the locomotive and the first passenger coach. As the fire did not occur in a tunnel it was relatively easy for the fire services to prevent the fire spreading and this event is regarded as a minor incident. The same situation, but with a much more severe fire, occurred in a train which collided with a tractor on the rail track.

Since 1921, no more than 20 severe fire incidents have been reported worldwide in railway tunnels, including both passenger and freight trains. This low number gives us an indication of the safety level of railway trains in general. But does this mean that we should be satisfied? We can choose to learn from these fires and through this, improve the fire safety further. But we can also choose to do nothing and say that this can not happen in our transport system or in our particular type of trains. What have we learned from these large fires? Whether or not a fire in a train develops into a more serious catastrophe depends on many factors. Key factors include:

• Where the accident has occurred
• The number of passengers
• The possibility to escape to a safe place
• The type and size of the ignition source
• The type and amount of flammable interior materials
• The ventilation and design of the train coaches
• The tunnel cross-section and the tunnel ventilation

The capability of the fire services to fight the fire also plays a significant role in the progression from a fire event to a catastrophic blaze.

Standards

There is a European CEN TS 45545 standard (draft enquiry version 2006) available, but manufacturers of trains and rail authorities relate performance to national standards, such as BS 6853 in UK, DIN 5510-2 in Germany and NF F 160-101 in France, as they are still waiting for full publication of EN 45545 in its adopted version. Various fire testing methods of different interior materials are given in these standards, and most of these standards aim to allow passengers to safely evacuate the train they occupy, in case of a fire.

Tunnel safety in railway tunnels in Europe is supported by the Directives 96/48/EC and 2001/16/EC on the Interoperability of the Trans-European rail system. Technical specifications for interoperability (TSIs) are being drawn up by the European Association for Railway Interoperability (AEIF) which act as the joint representative body defined in the directive, bringing together representatives of the infrastructure managers, railway companies and industry. The safety of railway tunnels outlined in the TSI covers the prevention and mitigation of incidents in tunnels, especially those originating from fire hazards. All relevant potential risks are addressed including those linked with derailment, collision, fire and release of dangerous substances. In the TSI (96/48-ST15EN03 RST – part2) for high-speed trains, national standards are allowed pending publication of EN 45545.

Research

Very few large scale tests have been conducted worldwide using burning trains in a tunnel. The most well-known is the EUREKA 499 fire test series1 conducted in an abandoned tunnel in Norway in 1991-1992. This was a European project and the results from these tests have been published and used widely. Researchers today, such as myself, still use these tests to obtain information about fire development in trains. The tests are based on experiments with single passenger coaches. The peak Heat Release Rates (HRR) were found to be in the range of 7 to 43 MW and the time to reach the peak HRR varies from 5 to 80 minutes. If the fire was to involve multiple cars, the total Heat Release Rate and the time to reach a peak Heat Release Rate would be higher.

Despite numerous investigations and experimental activities that have been performed, there is still a lack of knowledge concerning which parameters govern fire development in train coaches, and especially the fire spread between coaches. This is important knowledge, especially as many large infrastructure projects are dependent on so called ‘design fires’. The construction of the design fires varies a great deal, and the main reason is lack of experimental data and understanding of the main parameters controlling fire development. The maximum heat release design values for railway coaches varies, values of 2, 5, 10, 15, 25, 35 and 40 MW are all cited. For locomotives these values are variously cited as 7, 12, 20, 25 or 30 MW. For subway coaches the corresponding values are 8, 15, 30 MW while for freight trains they can be 8 or 52 MW.

Recently, the author published a scientific paper on model scale tests of train fires2. The advantage of doing model scale tests is the low cost.

Together with knowledge from real fire accidents, large scale testing and model scale testing, it is possible to point out the main parameters controlling fire development in a train coach. We know, for example, that the body type (steel, aluminium, glass-fibre etc) may affect the fire development. If the fire burns through the shell of the coach, the ventilation of the fire is increased and the fire can develop much faster. We know that the fire resistance features of the windows determine whether the windows will shatter. We know that the geometry of the openings (windows and doors) affect the fire ventilation and the possibility for the fire to continue growing. We know that the flammability and amount of interior material (fire load) affect the fire growth rate inside the coach and we know that the construction of coach joints affects the fire spread between coaches. One important piece of knowledge from real case studies is that many fires start under the coaches or in the locomotive and, from there, spread to the coaches. This is a fact that we need to deal with in fire safety standards for trains.

Extensive studies have been carried out by Peacock et al.3,4,5 to investigate the fire behaviour of American passenger railcars. The study, which included both small and large scale tests, demonstrated that a strong correlation exists between the small scale data of interior material and the flammability and smoke emission data obtained from other tests. This is a concept that has been introduced into American regulations6. A large research project on fire safety in trains (FIRESTARR) was carried out in Europe7. The FIRESTARR project was jointly funded by the European Commission and Industry. The main objectives were to identify the fire risks in European trains, to define the most relevant fire scenarios, to select the most suitable test methods for the assessment of reaction-to-fire behaviour and to propose a classification system for structural, furniture and electrotechnical material in trains. The results are the basis for future European requirements in EN 45545.

Summary

As far as fire research has been concerned, most of the work has been concentrated on the choice of interior materials in the coaches, rather than on the effect of the fire-separating integrity of the construction of the coaches. Research on the risk for fire spread between coaches is clearly lacking. Interior materials are a major factor in fire safety in trains and testing methods should obviously be used. The focus is on fire safety inside the train coaches and not the outside, despite the fact that there is a potential risk for large fires to occur under coaches. This becomes a problem when the trains are located in tunnels. The smoke can easily spread long distances, creating a hostile environment for those inside who have to evacuate through the tunnel. When the evacuation starts people have to escape through irritating and potentially toxic smoke with low visibility.

The role of the openings and interior surface materials on the fire development in trains needs to be investigated systematically. We need more large scale tests of real trains inside a tunnel. There are European initiatives on tunnel research ongoing under the umbrella of LSURF (Large Scale Underground Facility)8. This organisation could take the lead of doing such large scale testing. We also need to consider the possibility of using cost effective water spray systems and we must start to place requirements on the exterior construction of the coaches. The risk of serious fire in a carriage can be reduced by specifying the use of fire-classified windows in new carriages – which is not done today – and by increasing the fire performance of the body of the carriage itself during the design phase. Fire safety can be further improved by applying fire insulation to carriage bodies made of aluminium or reinforced glass fibre. This not only prevents a fire from burning through the body of the carriage and spreading to neighbouring carriages, but also prevents a fire that starts underneath the carriage from spreading up and into it.

References

1. “Fires in Transport Tunnels: Report on Full-Scale Tests”, edited by Studiensgesellschaft Stahlanwendung e. V., EUREKA-Project EU499:FIRETUN, Düsseldorf, Germany, 1995.
2. Ingason, H., “Model Scale Railcar Fire Tests”, Fire Safety Journal, 42, 4, 271-282, 2007.
3. Peacock, R. D., Averill, J. D., Madrzykowski, D., Stroup, D. W., Reneke, P. A., and Bukowski, R. W., “Fire Safety of Passenger Trains; Phase III: Evaluation of Fire Hazard Analysis Using Full-Scale Passenger Rail Car Tests”, Building and Fire Research Laboratory, NIST, NISTIR 6563, 2004.
4. Peacock, R. D., Reneke, P. A., Averill, J. D., Bukowski, R. W., and Klote, J. H., “Fire Safety of Passenger Trains; Phase II: Application of Fire Hazard Analysis Techniques”, National Institute of Standards and Technology, NISTIR 6525, 2002.
5. Peacock, R. D., and Braun, E., “Fire Safety of Passenger Trains, Phase I: Material Evaluation (Cone Calorimeter)”, NIST, NISTIR 6132, Gaithersburg, MD, USA, 1999.
6. “Research Results – Passenger Train Fire Safety”, In RR03-02, U.S. Department of Transportation – Federal Railroad Administration, 2003.
7. “FIRESTARR – Final report”, C/SNCF/ 01001, 2001.
8. http://www.l-surf.org/