Bimodal traffic evacuation management for road tunnels considering social fairness: CTM-based model

This study focuses on vehicle and pedestrian traffic management in freeway tunnels during emergencies such as fire propagation caused by traffic accidents. Such accidents can result in traffic breakdowns in a short time and a limited space, leading to severe health and safety issues. This study establishes a parsimonious bimodal tunnel evacuation management strategy that can provide real-time evacuation instructions by combining real-world historical traffic data and a cell transmission model (CTM). To exploit the evacuation capability of road tunnels with both vehicle cross and passenger passages, an equivalent cellular traffic network of a road tunnel and its escape facilities is first developed for bimodal evacuation. Simultaneously considering efficiency and social fairness in an emergency evacuation, a risk evaluation function is initially established and embedded in a system optimal objective function. The rationale of the proposed compact system models and the mechanism of effective traffic management measure generation is validated based on a real freeway tunnel emergency happened in Melba and Mullum-Mullum tunnels in Melbourne, Australia. The results suggest that the proposed CTM-based model has twinned the bimodal traffic characteristics and the flexibility to balance the evacuation efficiency and social fairness consideration in road tunnels under emergency conditions.