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January 26, 2020

 Road tunnels and technology in an operational perspective
Arild Petter Sovik, Tunntech Global News

Steeper tunnels can cause serious vehicle fires

Written by  Nov 09, 2017

Heavy vehicles are overrepresented in the statistics of fire in Norwegian road tunnels, and this is especially true for steeper tunnels. Technical problems was a more than twice a frequent cause of fires and instances of fires in heavy vehicles, than in light vehicles says the Institute of transport economics, Norwegian Centre of Transport Research. 40% of the fires in tunnels happens in tunnels with higher incline than 5%. 

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 a high incline over 5%, 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 gradient. 

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 incline/decline. Norwegian Public Roads Administration have started a survey to investigate key challenges with evacuation rooms and they will document if these rooms can be used in road tunnels in the future. 


  • A survey of vehicle fires in Norwegian road tunnels 2008–2011(the Institute of transport economics, Norwegian Centre of Transport Research).
  • Vehicle fires in Norwegian road tunnels 2008-2015 (the Institute of transport economics, Norwegian Centre of Transport Research).
  • Accident Investigation Board Norway

Weblink: https://www.toi.no/publications/vehicle-fires-in-norwegian-road-tunnels-2008-2015-article34094-29.html 

Last modified on Monday, 04 December 2017 15:42
Arild Petter Sovik

Editor, Tunntech Global News

E-mail:  arild.sovik@tunntech.no
Phone:  +47 950 88 793


News coverage based on many years of experience from key positions in the industry. Former National Tunnel Manager at the road authorities (NO), senior principal development manager at a major tunnel contractor company (NO) and experience from a wide number of activities in national and international networks. 


Website: www.sovikconsulting.no
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