Resilience analysis of road tunnels subject to refurbishment work.

After some tragic fire events, Directive 2004/54/EC was issued to ensure a minimum safety level for tunnels belonging to the Trans-European Road Network longer than 500 m. Nowadays, most of the Italian road tunnels are still not in compliance with the minimum safety requirements, thus refurbishment works are often planned. By developing a traffic macro-simulation model, this paper aims at assessing the resilience of an existing twin-tube motorway tunnel when one of its tubes is partially or completely closed due to planned activities. Several scenarios were investigated, also considering the availability or not of an alternative itinerary in the surrounding transportation network. The average vehicles’ speed was used as a functionality parameter, while the resilience metrics were the resilience loss, the recovery speed, and the resilience index. The findings showed higher resilience losses for complete closure rather than partial closure of the tube under planned refurbishment works. The implementation of digital technologies, such as variable message signs, might reduce the resilience loss of the tunnel system. This research might represent a reference for tunnel management agencies in the choice of the most appropriate traffic control strategy to improve tunnel resilience in the event of planned activities.