Norway has just experienced their 6th large scale fire the last 6 years, and this is the forth fire that can directly be linked to high gradient, in or before the tunnel. The Norwegian Public Roads Administration is well aware of these facts. Today, regulations and requirements for tunnel gradient in the tunnel are more stringent than ever, and there are several cases where the projects must return to the drawing board and begin to design a tunnel that gives a lower climb in the tunnel.
So how is the overall safety picture
Risk is the probability of an event occurring and consequence of such an event. Probability is linked to, among other things, traffic volume, traffic congestion and special features in tunnels.
Consequences can be significantly worse in the event of a road tunnel, and the characteristics of the tunnel will also affect this. Fire emergency preparedness in the area can also affect the consequences of fire in tunnels. Smoke is the main problem of a fire and the opportunity to reach another safe zone, which is not affected by smoke, is essential for the consequences of the incident.
Fire in a modern building will give those in the building a reasonable opportunity to escape to another safe zone. In a tunnel, you have to escape from your location to the portal outside of the tunnel. If there is an escape tunnel, this can be used. For long one-tube road tunnels this may be several kilometers away! Often an unreasonable prerequisite for safeguarding the principle of self-rescue.
Learning from the last fire
The Accident Investigation board wrote the following statement after the last fire in Oslofjordtunnelen (may 2017):
Course of events, fire location and type of vehicle was similar to the fire in 2011. Findings were made to suggest that engine breakdown caused this fire as well. This will be investigated further in the preliminary investigations. Fire extinguishing and evacuation seems to have worked as intended at this fire, and the damages on other road users were not severe. Installed aids and evacuation chambers seems to have contributed to this outcome.
Much indicates that the use of technology to detect fire early, initiate early closure, alert those in the tunnel about evacuation and led light leading to evacuation rooms have been good measures to reduce the consequences of fire in such a tunnel. In this case the road tunnel manager define evacuation rooms (with no access to the outside) to be a safe zone, and an effective measure to make sure that the principle of self-rescue is maintained. This is the first tunnel in Norway with evacuation rooms. There are restrictions in the tunnel safety directive, and such evacuation rooms shall not be build is stated in the directive.
The learning points for this fire will definitely give a discussion about how to design effective counter measures for tunnels with special characteristics like high gradient. Norwegian Public Roads Administration have started a survey to investigate key challenges with evacuation rooms and the NPRA will document if these rooms can be used in road tunnels in the future.