The optimization of preventive upgrading interventions on the bridges of a highway network in an earthquake prone area is tackled. The bridges are assumed to be the vulnerable elements of the network, whose main purpose is to connect two sites. If the probability of collapse of each bridge under an earthquake of given intensity is known, the topology of the network allows us to calculate its reliability, i.e., the probability of maintaining the connection between the source node and the destination node. To increase the reliability, preventive upgrading interventions must be designed: the main purpose of this study is to present a procedure, based on dynamic programming, which is able to distribute the interventions among the bridges so that, for a given total amount of employed resources, the increase in reliability is maximized. The applicability of the procedure is demonstrated by some complete numerical examples. Alternative choices of the objective function and other further developments are also discussed.
