Regulating Hazardous Materials Transportation by Dual-Toll Pricing and Time-Dependent Network Design Policies
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This dissertation develops three models for regulating hazardous materials (hazmat) transportation, addressing the applications of dual-toll pricing and time-dependent network design policies. The first part concentrates on the application of toll pricing as a policy tool to mitigate the risk of hazmat shipments by imposing separate tolls for the hazmat carriers and the regular vehicles. Two models are considered. The first model is a bi-level dual toll pricing problem under the consideration of nonlinear travel delay function. Despite the non-convexity of the first stage problem, a two-stage solution procedure that assures obtaining valid dual tolls is suggested. The second model is a general dual toll pricing problem minimizing the transport risk as well as the paid tolls which necessitates applying a single-level solution approach. A decomposition based heuristic algorithm utilizing a non-linear programming scheme is developed for its solution. A case study on the application of the two proposed frameworks is presented for the road network of city of Sioux Falls, SD. The second part develops the time-dependent hazmat-network design problem providing the regulator with the time-dependent road closure policy for reducing hazmat transport risk, and allowing the carriers to postpone their trips towards minimizing the transportation cost. The bi-level framework of the problem is formulated as a single-level alternative-based model, with an alternative comprising of a route and a departure time from the origin. A column-generation-based heuristic algorithm embedding two sub-problems is proposed for solving the problem. To directly address the carriers' concerns surrounding the economic viability of the produced design polices, a set of constraints are incorporated into the model to restrict the regulator's legislation power. Two case studies on the networks of cities of Buffalo, NY and Sioux Falls, SD are carried out to illustrate the viability of the proposed algorithm as well as the capability of the model in generating mutually acceptable design policies for the carriers and the regulator. The third part expands the effectiveness and the applicability of the design polices generated by the second model. Two extensions are considered; the time-based road-closure policies are restricted to be consecutive, and waiting at intermediate nodes is allowed in generating routing and scheduling decisions of the carriers. The first extension is incorporated by introducing sets of constraints to the original model. To allow stopping en route in the decisions of the carriers pertaining to the second extension, a label setting algorithm which allows imposing complex constraints on waiting and driving times is proposed. A case study on Buffalo, NY presents the findings under different versions of the time-dependent hazmat-network design problem.