Method of generating strategic guidance information for driving evacuation flows to approach safety-based system optimal dynamic flows: Case study of a large stadium

In previous evacuation flow planning, a system optimal dynamic traffic assignment (SO-DTA) did not consider the exogenous costs caused by potential traffic accidents. A traffic accident, which might occur as a result of traffic congestion, will impact an evacuation process because of accident-related delays experienced by the downstream vehicles. This paper establishes a safety-based SO-DTA linear programming model in which the generalized system cost incorporates both the travel time and the accident-related delay. The goal is to minimize the generalized system cost under the cell transmission setup. Furthermore, the authors provide strategic guidance information that considers both the objective of the decision maker and the route choice behavior of the evacuees. Mathematically, the authors propose an unconstrained non-linear programming model aimed at minimizing the gap between the safety-based flows and the stochastic real-world evacuation flows, to provide strategic travel time information to be published on variable message signs (VMS). In the case study, the authors found that the safety-based SO-DTA model can reduce congestion and improve the evacuation efficiency; the stochastic real-world evacuation flows, guided by strategic information, can approach the safety-based flows.