Risk analysis and optimization of road tunnels

Probabilistic methods of risk optimization are applied to identify the most effective safety measures applied to road tunnels. The total consequences of alternative tunnel arrangements are assessed using Bayesian networks supplemented by decision and utility nodes. It is shown that the probabilistic optimization based on the comparison of societal and economic consequences may provide valuable information enabling a rational decision concerning effective safety measures. A general procedure is illustrated by the optimization of a number of escape routes. It appears that the discount rate and specified life time of a tunnel affect the total consequences and the optimum arrangements of the tunnels more significantly than the number of escape routes. The optimum number of escape routes is also significantly dependent on the ratio of cost of one escape routes and acceptable expenses for averting a fatality. Further investigation of relevant input data including societal and economic consequences of various hazard scenarios is needed.