Integrated dual toll pricing with network design for hazardous materials transportation

The goal of this paper is to propose an effective traffic control policy for hazardous materials (hazmat) vehicles to enhance public safety with minimal sacrifice in terms of traffic efficiency, by managing traffic flows in tollways and freeways together. To devise such a policy, a two-stage simulation-based optimization approach is proposed considering two different policies simultaneously: 1) Network Design (ND) which restricts hazmat transportation from freeways in densely populated areas; and 2) Dual Toll Pricing (DTP) which levies toll on hazmat vehicles as well as regular vehicles in tollways. Besides, an Agent-Based Simulation (ABS) technique is adopted in the proposed approach to evaluate the suggested policy under realistic traffic conditions on a highway. The proposed two-stage approach allows us to reduce a large search space involved in the considered optimization: the first stage categorizes freeways into two classes (i.e., restricted and unrestricted roads) via ND to reduce road risk caused by accidents of hazmat vehicles, and the second stage executes DTP to minimize the total traveling cost of both regular and hazmat vehicles. The proposed approach has been implemented in AnyLogic® ABS software with a real traffic data of San Antonio, Texas. In addition, Particle Swarm Optimization (PSO) has been used to find the optimum ND and DTP policies under the AnyLogic® ABS model. The experimental results reveal that the proposed simulation-based optimization approach is able to efficiently reduce the risk of hazmat transportation regarding both tollways and freeways.