Risk Assessment for Transportation of Hazardous Materials Through Tunnels

Two vehicle collisions involving hazardous materials (HM) occurred in 1999 in the tunnels of Mont Blanc between Italy and France and in Tauern, Austria. These collisions showed that the consequences of such crashes are catastrophic for both the motorists in the tunnel and the tunnel itself. This paper presents a methodology to help decision makers estimate the risk associated with the transportation of HM through tunnels and identify remedial measures to minimize unacceptable risk levels. A risk assessment procedure is used to identify the societal risk of the tunnel. If the risk is above an acceptable level, alternative routes are considered, and the overall risk is estimated for both the route with the tunnel and the alternative routes. The route with the minimum risk is established. If the route of minimum risk is through the tunnel, then risk reduction measures are introduced and the risk assessment methodology is implemented to verify the result. The full implementation of the methodology is demonstrated in a case study. The characteristics of the tunnels, the type of HM, and the characteristics of the traffic and accident risk at each tunnel are accounted for. Given an estimate of risk for a tunnel produced by the analytical procedure used in this paper, the applicable regulatory criteria at a given location are found to substantially affect the required response. The response may vary from "no restriction to HM traffic," to "remedies required," to "total restriction of HM type X is advised" for the subject tunnel. The case study considers several remedial actions and assesses their impact on risk and subsequent recommended actions.