Probabilistic risk optimization of road tunnels

Probabilistic methods of risk optimization are applied to identify the most effective safety measures considered in the design of 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 of societal and economic consequences may provide valuable information enabling a rational decision concerning effective safety measures in road tunnels. A general procedure is illustrated by the optimization of a number of escape routes using the concept of life quality index. It appears that the discount rate and specified life time of a tunnel affect the total consequences and the optimum arrangements of the tunnel more significantly than the number of escape routes. Further investigation of relevant input data including societal and economic consequences of various hazard scenarios is needed.