Solving a NewVehicle Routing Problem Considering Safety in Hazardous Materials Transportation: AReal-case Study

Transportation of hazardous materials plays a significant role in economic activities in developing as well as developed countries because of the need of industrial plants to these materials. In many cases, production plants of hazardous materials are far from the consumers, wheretransportation of materials affects the safety of the people involved. In this paper, besides minimizing the cost of related transportation, reduction of accident probability as minimizing the risk of hazardous materials transportation, is also considered. The  importance of required time formaterials delivery is another main objective. The above issue is categorized in a vehicle routing problem with time windows (VRPTW). In this paper, a newmulti-objective mathematical model is presented and solved by the use of a well-known evolutionary algorithm, NSGA-II. Related computational results are compared by results of Lingo software using the ε-constraint method in small-sized test problems. A number of numerical investigations to evaluate the quality of solution sets versus time in large sizes are performed on various test instances. Results obtained by NSGA-II were compared based on two comparison metrics, namely spacing and quantity, in order to show the efficiency of the proposed NSGA-II. Finally, a real-case study was considered for shipping theChlorinegas capsulesfrom the Water & Wastewater Company to municipal water treatment facilities in Tehran.