A Two-echelon Vehicle Routing Problem with time-dependent travel times in the city logistics context

The fast rates at which urban population is growing coupled with increasing demands expressed within cities have given rise to challenging freight transportation problems. The Two-echelon Vehicle Routing Problem (2E-VRP) has been proposed as a scheme to tackle city-related problems. To better evaluate its pertinence in large congested city areas, this work addresses a version of the 2E-VRP in which synchronization is required among the two echelons. Besides, it considers time-dependent travel times at both echelons as well as time windows at customers. Other characteristics such as open routes at second echelon offer a degree of flexibility on the efficiency of the distribution specially when dealing with outsourcing schemes. The primary goal is to minimize the number of vehicles. Meanwhile, travel and waiting times, as well as penalties for late deliveries are minimized as a secondary objective. A two-phase metaheuristic approach is proposed to solve the problem on existing benchmarks; as well on a new set of instances based on real information from the city of Bogota, provided by an industrial partner. The experiments prove that including time-dependent travel times is of utmost importance for practical applications.