Preliminary study on the transport of hazardous materials through tunnels

Long distance road and rail transportation of hazardous materials in Europe often include the passage through tunnels. Generally speaking, road and rail transportation of such products is ruled by ADR and RID codes, respectively; however, these documents do not provide any indications related to the passage of vehicles carrying dangerous goods through tunnels. As a matter of fact, a study concerning road tunnels (OECD, 1997) showed that, in most of the 21 investigated Countries, no general code exists, but only a few regulations relevant to specific tunnels: hazardous materials are divided into classes, whose passage in the tunnel may be free, limited or forbidden. It is clear that the subject is rather complex and that a sound approach to the problem should be based on risk analysis. In fact, forbidding to hazardous materials the passage through tunnels, from one hand will increase the safety of tunnel users, but, on the other one, will submit to additional risk the population living or travelling along the alternative (and, usually, long) route followed by the vehicle to avoid the passage through tunnels; generally, these alternative paths will cross a number of urban sites where the consequences of an accident may affect a greater number of people with respect to tunnel users. The paper will present some comparison between the transport of different hazardous materials along possible alternative road and rail route including or not including tunnels, based on the calculation of the respective societal risk curves. To this end a software for risk assessment and management, TrHazGis (Bubbico et al, 2004), will be used. The tool, which presently include all needed information (probabilities and impact areas of the accidental scenarios, local incident rates, weather conditions, on-route and off-route population) for open sections, will be modified to account for the values of these parameters in tunnels. In particular, the impact areas will be calculated for some tunnels typologies using simplified models (OECD, 2003), and specific values of incident rate, accidental scenarios probabilities and on-route population will be estimated. The study will give useful information to properly select minimum risk routes for hazardous materials transportation, when the passage through tunnels may be involved