Accepted Manuscript This is an Accepted Manuscript of the following article: Nævestad T O, Meyer S. A survey of vehicle fires in Norwegian road tunnels 2008–2011. Tunnelling and Underground Space Technology. 41 (March), 2014, 104-112. 0886-7798 The article has been published in final form by Elsevier at http://dx.doi.org/10.1016/j.tust.2013.12.001 © 2013. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ It is recommended to use the published version for citation. The final publication is available in Tunneling and Underground Space Technology, Vol 41, pp. 104-112; https://doi.org/10.1016/j.tust.2013.12.001 Vehicle fires in Norwegian road tunnels 2008-2011 Tor-Olav Nævestad and Sunniva Meyer Institute of Transport Economics, Gaustadalléen 21, NO-0349 Oslo, Norway, Tel.: +47 22573800, fax: +4722609200, E-mail address, corresponding author: [email protected] Abstract Norway is one of the countries that constructs the most road tunnels, and there are well over 1,000 in the country. The aim of the study is to map the prevalence and describe the characteristics of vehicle fires in Norwegian road tunnels 2008-2011. The average number of fires in Norwegian road tunnels is 21.25 per year per 1,000 tunnels, and the average number of smoke without fire is 12.5 per year per 1,000 tunnels. The fires and the instances of smoke without fire do usually not involve harm to people or the tunnels. Of the 135 fires and instances of smoke without fire, we know that 8 involved minor injury to people and that 3 involved serious personal injury and 5 involved death. The present study provides two important findings. The first is the fact that the causes of fires in heavy and light vehicles are different. Technical problems are the most frequent cause of fires and instances of smoke without fire in heavy vehicles, while single vehicle and collisions are the most frequent cause of fires in vehicles weighing less than 3.5 tonnes. The second important finding of the study is that undersea tunnels are substantially overrepresented in the statistics of fires in Norwegian road tunnels. There are 31 undersea road tunnels in Norway. These have a high gradient, defined as over 5 %. In addition, there are 10 tunnels that are not underwater, but still have a high gradient. These 41 road tunnels, which together constitute 4% of road tunnels in Norway, had 44% of the fires and the instances of smoke without fire in the period 2008-2011. Heavy vehicles were overrepresented in these fires, and technical problems were the most frequent cause. 1. Introduction 1.1 Aims and methods Norway is one of the countries that constructs the most road tunnels (Amundsen & Ranes 1997). There are well over 1,000 in the country. Road tunnels are usually at least as safe as or safer than similar roads in the open air without junctions, exits, pedestrians and bicyclists (Amundsen & Engebretsen 2009). Road tunnels do nevertheless deserve attention from a traffic safety perspective, because of their disaster potential related to vehicle fires. 1 Road tunnel fires make up a substantial potential for catastrophe on the Norwegian road network. Although international research indicate that vehicle road tunnel fires seldom occur, these incidents constitute a particular risk, as they usually involve substantial release of smoke and heat (PIARC 2008; Stene, Jenssen, Bjørkli & Bertelsen 2003). Although the vehicle accident risk is lower in road tunnels than it is on the remaining road network, the catastrophe potential related to tunnel fire is higher (Jenssen, Bjørkli & Flø 2006: 16). This is indicated by the three catastrophic road tunnel fires in Central-Europe at the turn of the century; in the Mont Blanc tunnel, the Tauern tunnel in 1999 and in the St. Gotthart tunnel in 2001 (Stene, Jenssen, Bjørkli & Bertelsen 2003). The aim of the study is to map the prevalence and describe the characteristics of vehicle fires in Norwegian road tunnels 2008-2011. The following fire characteristics are examined: 1) time of the fire 2) location of the fire, 3) scope of the fire: people and vehicles involved, personal injuries, vehicle and tunnel damages and for how long was the tunnel closed? 4) how was the fire extinguished?, 5) how was the road traffic centrals alerted about the fire?, 6) cause of the fire and 7) undersea tunnels. The project is based on the following data sources: 1) “Merkur” (2001-2008) and “Vegloggen” (2008-today), that are the Norwegian road traffic centrals’ (RTC) systems for recording road incidents, 2) road traffic central personnel, 3) Norwegian Public Roads Administration (NPRA) personnel working with road tunnel safety, 4) fire services in all municipalities with road tunnels and 5) news archives 1.2 Previous research on road tunnel accidents and fires Road tunnels have fewer accidents per vehicle/km than comparable road stretches in the open air, as several accidents occurring out on roads in the open air seldom occur in road tunnels (Amundsen & Engebretsen 2009). The accident severity of the most common road tunnel accident is, however greater than the severity of accidents occurring on open air roads (Nussbaumer & Nitsche 2008). The vehicle accident risk and severity differs greatly in different tunnel zones (Amundsen & Engebretsen 2009). The vehicle accident risk of the entrance zones of road tunnels (e.g. the first 100 metres) is often 3-4 times higher than it is further into the tunnels, while the accident severity is highest in the central zone of road tunnels. The high entrance zone accident risk is probably due to impaired light conditions in tunnels compared with open air (a “black hole effect”), which make drivers lower their speed, and change lateral position (Amundsen 1994; Sagberg, Hakkert, Larsen, Leden, Schmotzer & Wouters 1999). Road users braking as they enter road tunnels may induce a higher accident risk. Road tunnels comprise a “poor sensory environment” compared with roads in the open air, and this may lead to, monotony lowered driver attention, disorientation and/or fear (Jenssen et al 2006: 26). The lack of references in road tunnels may also make drivers’ assessments of speed and distances poor. Finally, drivers rate 2 road stretches in the open air higher than tunnels when asked about desirable road environments. Undersea tunnels are rated lowest among road users (Jenssen et al 2006: 12). Amundsen and Engebretsen (2009) have studied accidents in Norwegian road tunnels 2001-2006 and conclude that the three most common accident types in road tunnels are: collisions between vehicles driving in the same direction 43 % (rear end or changing lanes), single vehicle accidents 35 % and head on collision 15 %. A previous analysis of Norwegian tunnel accident data 1992-96 conclude that rear end collision is the most common road tunnel accident type, occurring twice as often in tunnels as in the remaining road network (Amundsen & Ranes 1997). Norwegian studies indicate that heavy vehicles are overrepresented in road tunnel accidents. The share of heavy vehicles involved in road tunnel accidents (22 %) is twice as big as the traffic amount and accident share on roads in the open air would imply (Amundsen 1996). The steep inclination of undersea road tunnels seems to involve a higher vehicle fire risk for heavy vehicles, as their brakes may overheat driving down into tunnels, and as their engines may overheat driving up and out of the undersea tunnels. This argument is underlined in the investigation report of the fire brigade of ”Søndre Follo” (2011) following the Oslofjord tunnel fire 23.06.2011. According to this report, the undersea Oslofjord tunnel experienced 11 fires in the three years preceding the 23.06.2011 fire. Eight of the fires were in heavy vehicles, while three of the fires were in personal cars. Two thirds of the fires in the heavy vehicles were caused by overheated brakes, while one third was caused by overheated engines (Søndre Follo Brannvesen 2011: 9). SAFETEC’s risk analysis following the 23.06.2011 Oslofjord tunnel fire suggests that foreign lorries seem to have a higher risk of vehicle fires in Norwegian undersea road tunnels (SAFETEC 2011). The foreign lorries have two axles, weaker engines and they are generally older than Norwegian lorries. The demands on the foreign lorries increase when they are used in hilly terrain with heavy loads. This applies to Scandinavian terrain in general, but especially steep undersea road tunnels. Scandinavian lorries are better adapted to the Scandinavian topography. They are equipped with three axles and have more powerful engines, reducing the risk that they are over loaded in hilly Scandinavian terrain. Additionally, Scandinavian lorry drivers are probably more experienced with and more competent with regard to driving on Norwegian roads. As a consequence, they probably apply the brakes more correctly driving downhill in road tunnels, minimizing the risk of overheated brakes (SAFETEC 2011). A 1992 publication from the NPRA sums up the road tunnel fire research to conclude that the risk of road tunnel fire is 0,01 instances of fire per 1 million vehicle hours. These data indicate that most of the fires occur in cars, and that the fires usually are extinguished by the driver or by other people. The 1992 publication from the NPRA asserts that the most frequent causes of vehicle tunnel fires are defects in the electric system, or the petrol supply. Moreover, it is reported that the fires seldom cause personal injuries (NPRA 1992: 2). 3 International research indicates that the most common causes of vehicle road tunnel fires are mechanical or electrical defects in vehicles (PIARC 2008: 61).