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A New Method of Risk Assessment when Fighting Tunnel Fires

by Marcus
Risk Assessment when Fighting Tunnel Fires

This article looks at a new method of risk assessment when fighting tunnel fires.

Fires in road tunnels can be very serious and difficult to fight. In addition to the necessary resources, there must also be proper incident planning. SP has carried out an investigation into how best these problems can be solved.

We suggest a classification system that takes account of the time taken for the rescue services to reach the site, possible accident scenarios, the type of tunnel and the traffic situation. This classification system can provide important assistance to road authorities when holding discussions with fire and rescue services before the construction of a tunnel.

Important safety aspect

The serious tunnel fires that have occurred in Europe have concentrated attention on the problems that the fire and rescue services face when tackling fires in road tunnels. They need to be capable of adjusting their response to suit different conditions. Very little research into this has been conducted to date, although it is widely accepted that this is an important safety area, not just for the fire and rescue services but also for tunnel users, tunnel operators and tunnel owners.

Risk Assessment when Fighting Tunnel Fires

An exercise in the Southern Link tunnel in Stockholm.

Image: Risk Assessment when Fighting Tunnel Fires

In our investigation we studied accidents that had occurred in road tunnels. From this we could identify four accident scenarios, with the choice depending on whether the fire had started in an individual vehicle, or as a consequence of a collision between vehicles. The risk of a large, extensive fire is considerably greater if it is the result of a collision. The types of vehicles involved are also significant. For each accident scenario, we have developed different potential heat release rate curves. The reason for distinguishing between accident scenarios and fire scenarios is that there are several different parameters that determine which fire scenario is the most likely. The scenarios will be used as input data for assessing the risks and opportunities for tackling fires in the particular tunnel concerned. Tunnels in which there is a substantial risk of a catastrophic fire require more comprehensive countermeasures in order to reduce the risks of serious consequences.

This can be done both by taking steps to reduce the risks of an accident, or by limiting the consequences of a fire through appropriate planning, tactics, resources or physical installations/services.

Four classes

We therefore suggested four classes of tunnels in order to assess the risks associated with fire fighting in road tunnels. The choice of class depends on the type of traffic (large vehicles, types of loads, queue formation), the type of tunnel (unidirectional or bidirectional traffic), the physical equipment installed in the tunnel (sprinklers, ventilation), the time taken for the fire and rescue services to reach the site, possible accident scenarios and fire scenarios. All these factors are considered in order to decide the class to which the tunnel belongs. The lowest risk class presupposes that the fire and rescue services are capable of tackling all types of fires. Installation of a sprinkler system can affect the class rating of the tunnel. Tunnel owners and fire and rescue services can use the classification system in their discussions to select appropriate physical safety systems and to make assessments concerning the necessary response times and strategies.

One of the authors of SP Report 2010:10, Effective Fire fighting Operations in Road Tunnels, Hak Kuen Kim, works for the fire and rescue services in South Korea, but took part in SP’s work of the study when working with SP as a guest researcher.

Article from Brandposten magazine from SP Technology

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