Preliminary study on the transport of hazardous materials through tunnels.

The risk associated to road and rail transportation of some hazardous materials along two routes, one including a significant portion in tunnels, and the other following the same path, but running completely in the open, is assessed. The results show that, for rail transport, no particular risk increase or mitigation is associated to the circulation of the dangerous goods through tunnels; on the contrary, for road transport, a risk increase is generally observed in the presence of tunnels. However, for LPG, the risk curve in the open lies above that in tunnels in the high frequency-low fatality zone, according to the different evolution of the accidental scenarios in the tunnel (assuming no ventilation). The transportation of liquefied nitrogen, not hazardous in the open but potentially asphyxiating in a tunnel, gives rise to a negligible risk when performed by rail, but to a not negligible one, when performed by road. These preliminary results focused on the risk for the exposed population, suggest that it may be unnecessary to limit dangerous goods circulation through rail tunnels, while, at least for some types of dangerous goods, the circulation through road tunnels may be allowed/forbidden based on the results of a specific risk analysis.