Sustainable vehicle-routing problem with time windows by heterogeneous fleet of vehicles and separated compartments: Application in waste collection problem

This study aims to solve a sustainable vehicle routing problem (VRP), where special characteristics such as mixed close and open routes, and several servicing depots in different areas are considered for achieving to real life conditions. Fleets of vehicle are heterogeneous, and specified capacity for each type of waste is assumed in this paper. Vehicles have different attributes such as limitations on traveling time, fixed and variable cost, and amount of pollutants emitted to an environment. For achieving a sustainable collection network, economic, environmental, and social aspects should be considered, simultaneously; therefore, in this paper three different objective functions are optimized at the same time. The first one minimizes the cost of collecting wastes from customers’ location. The second one minimizes the pollutants emitted from vehicles while they are collecting wastes, and finally the third one minimizes violation from servicing time limitations. A new mathematical mixed integer programming model is developed for solving this problem, and the problem is tackled by CPLEX solver and augmented ɛ-constraint method. Moreover, AHP technique is applied in order to help us to choose the best decision. Finally, sensitivity analysis is done on some important parameters.