A customized bi-objective location-routing problem for locating post offices and delivery of post parcels

One of the most important problems for distribution companies is to find the best locations for depots and to find proper routes for transportation vehicles to optimize their supply network. This study intends to develop a model for the problem of location-routing in post offices. So, a new bi-objective locationrouting problem for locating town post office and routing parcels is defined. This problem is modeled through the mixed-integer mathematical programming. The aim of the proposed model is to select potential post offices and to find optimal routes for transportation vehicles whiletime constraints are taken into account. The proposed model is applied in a real case study including eight main post area and 21 regional offices in Tehran, Iran. A goal programming approach is proposed to solve this bi-objective optimization model. An optimization Software is used to code and solve the associated mathematical model. Some required parameters of the model such as demands are estimated using Geographical Information System (GIS) and simulation methods. The results of proposed model including the objective functions, decision variables, and proposed routing of vehicles have been compared with the existing practical solutions. Sensitivity analysis on main parameters of the proposed models is accomplished and the results are analyzed. This comparison illustrates the efficacy and applicability of our proposed approach.