Fighting Tunnel Fires

14 October 2010 (Last Updated October 14th, 2010 18:30)

As rail safety standards become stricter, engineers and maintenance professionals must optimise protection systems. We speak to a top European fire safety expert to uncover the latest techniques and technology.

Fighting Tunnel Fires

As Arena International prepares for its second annual Fire Protection and Safety in Tunnels event, we track down European rail group RFI's safety assessor and engineer Marco Cigolini. Ahead of his presentation to delegates at the event, where he will focus on cost and benefit analysis for the retrofit of old rail tunnels, he exclusively tells his views on safety issues affecting Europe today, including some of the top technologies available and why he thinks rail safety has improved across the continent.

Railway Technology: What do you do as a safety assessor and engineer?

Marco Cigolini: Basically a fire protection engineer performs hazard assessment through the application of regulation and standards or by the application of predictive tools, in order to find design solutions.

Looking specifically at the following areas: active fire protection - fire suppression systems and fire alarms; passive fire protection - fire and smoke barriers, space separation, smoke control and management; infrastructure design, layout, and space planning; fire prevention programmes; fire dynamics and fire modelling, human behavior during fire events and risk analysis, including economic factors.

RT: Can you name the biggest areas of risk when assessing safety for rail tunnels?

"A fire protection engineer performs hazard assessment through the application of regulation and standards."

MC: Large fires are definitely one of the biggest hazards for rail transportation in tunnels, but are fortunately very rare. Accidents involving trains carrying dangerous goods can lead to large fires in cases of significant leakage of flammable gas or liquid.

Incidents such as this can have significant consequences for passenger safety, with fatalities possible in the case of a fire accident involving dangerous goods while a passenger train is approaching on the adjacent track.

Threats can spread along the tunnel, towards an oncoming passenger train. In the event of such a fire, it is crucial to ensure that passengers can reach an exit before conditions become dangerous. This must be accurately investigated.

RT: Can you outline the main common elements of such an accident?

MC: The sequence of a tunnel derailment of a train carrying dangerous goods can be outlined according to key events (or subevents), like a tank derailment, providing mechanic shocks to the vessel and leading to a leakage of flammable gas or liquid, which can consequently all the formation of a pool of condensed gas or liquid, before initiating a fire involving the flammable liquid itself, which can arise from the sparks and hot spots created by the mechanical dynamics involved in the derailment, or from the electric power supply, if present.

The expected HRR peak values, in the case of pool fires in a railway tunnel involving significant amounts of flammable liquids, can be roughly estimated to be in a range of 50MW–200MW; nevertheless geometric characteristics of the tunnel, the pavement or the trackbed ballast layer where the liquid accumulates and the tanks capacity can significantly influence the HRR curve.

RT: Do you think the financial climate is having an impact on any aspects of fire safety regulation?

MC:Safety regulation determines the acceptable safety levels for a country, but, of course, economic conditions do have a direct influence on fundamental variables like the traffic volume and, consequently, on the "price" of safety.

Safety regulation in my opinion should not follow the economic trend, but lead to a constant enhancement of the level of safety. Dangerous situations can be determined after any recession, while traffic volumes return to previously higher values.

RT: In your opinion, what are some of the top technologies and strategies for fire prevention and suppression to protect rail tunnels?

MC: Regarding passenger trains, systems aimed at automatically driving the train toward the closest "safe point" when a fire is detected, together with appropriate fire compartments and materials, can be a top strategy.

In the case of freight trains, the best technologies would include the enhancement of any measure aimed at reducing the expected frequency of such events of ignition in tunnels (caused by possible leakage of flammable gas or liquid, or derailment). Advanced detection technologies can help in this sense, but even more important are appropriate guidance and codes of practice relating to maintenance procedures.

RT: Are there any outdated technologies that should be discarded? If so, what are they?

"Large fires are definitely one of the biggest risks for rail transportation in tunnels."

MC: Taking into account the resources of the country will generally indicate if they are outdated. Some older technologies are still being used, which may compromise safety and increase the level of risk.

Personally, I think that any technology related to signalling systems should be replaced with newer and safer systems as a priority, in order to avoid hazards arising from the failure of such subsystems, usually followed by catastrophic consequences.

RT: How can Europe's safety legislation be improved?

MC: I see a lack of facilities for socially vulnerable groups; those with disabilities, children and young people. Moreover I would like to see an effort at encouraging inter-modal or co-modal transport solutions.

RT: What would you like to see legislators across Europe do to enhance rail safety procedures and reduce accident levels?

MC: EU Directive 2008/57/EC, through the introduction of TSIs (technical specification for interoperability) and the procedures arising from the 2004 directive concerning the process of authorisation for placing in-service subsystems and vehicles could also lead to an enhancement of railway safety levels.

Nevertheless, the development of appropriate procedures to further reduce the human factor that can affect maintenance activities should continue to be encouraged.

RT: Do you think rail safety overall has improved across Europe and what has been the impact of tunnel technology on this?

MC: Accident statistics seems to show that overall safety has improved, with tunnel configurations like the double bore and the double bore with service tunnel (although expensive) significantly contributing to increased rail safety.

Arena International's second annual Fire Protection and Safety in Tunnels event will be held 26-27 October in Milan.