Covering vehicle routing problem: application for mobile child friendly spaces for refugees

The world is facing a large-scale refugee crisis because of the ongoing war in Syria, and it is important to improve refugees' life conditions from a humanitarian point of view. In order to analyse the living conditions of refugees, we conduct fieldwork in a district in Ankara, Turkey, and interview refugees, the local population and humanitarian practitioners from several organizations. Among the many challenges refugees face, we observe that addressing the problems of refugee children is critical. Thus, in this study, we focus on increasing the efficiency of the education services provided to refugee children. We investigate a service provided via mobile trucks that supply informal education and psychological support to children. By analysing the operational dynamics of these trucks, we introduce two problems to the logistics literature, which we refer to as the covering vehicle routing problem and the covering vehicle routing problem with integrated tours. In the first problem, we either visit or cover all nodes, such that every node not in one of the tours is within a predetermined distance of any visited node. In the second problem, we generate smaller tours for covered (or unvisited) nodes originated at the visited ones. We first propose mathematical models for the problems and then introduce heuristic methods to overcome the computational challenge of the second problem. In the computational study, we compare the optimal solutions obtained using the models with a solution of real-life application. We then test the models and heuristics on medium and large real data sets gathered from Turkey and conduct sensitivity analysis on the model parameters.