Workload Equity in Vehicle Routing with a Medium-Term Perspective

In the vehicle routing literature, equity for drivers is mostly considered on a daily basis. In this work, we extend the literature by addressing equity on a longer term. We consider a time horizon of a few weeks and a test-bed routing problem motivated by healthcare logistics, with customer demand progressively revealed. Having unbalanced routes at some periods (days) is accepted, but some degree of equity is imposed on the complete horizon. We propose five solution frameworks with different levels of control on equity. A dedicated branch-and-price algorithm is used to solve the daily routing problem and is adapted for the different solution frameworks. Numerical experiments are conducted on a benchmark of realistic instances to evaluate how addressing equity this way impacts the routing cost, equity and feasibility