Sürdürülebilir gıda tedarik zincirlerinde zaman pencereli ve eşzamanlı toplama-teslimatlı kapasite kısıtlı bir araç rotalama problemi

The aim of our study is transportation planning in perishable food supply chains. We model this problem as the vehicle routing problem with simultaneous pickup and delivery, and soft time windows for perishable products (VRPSPD-STW-P). The objective is to minimize the total costs, consisting of variable transportation costs, vehicle-related fixed costs, food quality degradation costs, and time-window violation costs. We formulate the problem as a mixed-integer linear programming model. Moreover, we propose heuristic and metaheuristic algorithms in the methodology to solve the VRPSPD-STW-P. Our methodology comprises two phases: obtaining initial solutions in the first phase and improving these solutions by a genetic algorithm in the second phase. In these phases, we first employ a method based on the clustering of nodes for the vehicles and different routing heuristics to generate the best routes for the vehicles; that is, solving the problem as an m-traveling salesperson problem with simultaneous pickup and delivery (m-TSPSPD). Then the solution of the problem m-TSPSPD is checked for feasibility taking into account the vehicle capacities and tour lengths; the feasible routes are then the solutions for the vehicle routing problem with simultaneous pickup and delivery (VRPSPD). Finally, the VRPSPD solution is evaluated considering the time window and quality constraints (VRPSPD-STW-P). Our solution methodology yields promising solutions in much less computational time than the solutions generated by the exact solution procedures.