Traffic-based resilience assessment on urban road tunnel affected by fire accident

Fire accidents could significantly disrupt the operation of urban roads, especially when they occur at critical routes, such as tunnels. However, due to a lack of systematic studies on the traffic demand affected by tunnel fires, it is challenging to properly define an indicator on traffic performance during accidents, as well as investigate the development of traffic performance in the disruption and recovery stage. In this paper, a traffic-based resilience assessment model was proposed, considering both the accident duration and distribution of traffic demand. In this model, the influence of factors, such as tidal traffic flow and traffic capacity could be intuitively reflected. Besides, the disruption and recovery process of traffic performance could be accurately predicted. Firstly, the methodology for developing the proposed resilience assessment model was discussed in details. Subsequently, a case study focusing on a cross-river tunnel in Shanghai was conducted to exhibit the application. Then, the evolution of performance curves and resilience assessment under different conditions, such as time of fire accident, fire intensity and distribution of traffic demand were investigated. Finally, effectiveness of two measures on improving traffic resilience, including enhancing overall efficiency of emergency services and conducting traffic managements in time was discussed. The results indicate that resilience decreases when fire accidents occur during holidays, or at times when traffic demand is high. Besides, taking traffic managements in time could significantly enhance resilience, with potential improvements of up to 57.5%. This study contributed to the research on recovery of tunnel traffic under fire conditions and future studies on urban road traffic resilience.