Impact Mitigation of Tunnels Maintenance Works on Highway Performance

Major maintenance interventions on highways (e.g., for the safety improvement of tunnels and viaducts) involve the presence of work zones for extended periods of time and along wide sections of the infrastructure. These interventions lead to supply changes, especially a reduction in capacity, causing a decrease in the performance of the transportation system, which users experience with increased traffic congestion and economic losses in terms of productivity. This paper aims to demonstrate that proper traffic management and work zone planning allow for a significant reduction of such impacts. In relation to traffic management, possible solutions consist of diverting traffic flows onto alternative routes (if possible, using primary roads) or keeping them in the remaining lanes along the work zone. In terms of work zone planning, leverage can be applied, on the one hand, through the design of the work zone layout and maintenance scheme and, on the other, through the duration and scheduling of the interventions. The methodology proposed in this paper is based on traffic simulation models in order to assess different maintenance scenarios under varying demand levels (i.e., during the rush hour and off-peak hours, weekdays and weekends, summer and winter months) and vehicular compositions (i.e., percentage of heavy vehicles), with the goal of identifying the scenario that minimizes the impacts on users. Modelling evidence on a real case study of tunnel maintenance interventions on an Italian highway is reported, discussing the policy implications on the basis of quantitative indicators, such as level of service, duration of delays, length of queues, and economic impacts.