Electric vehicle routing problem – a nested two level approach

Some of the main constraints of electric vehicles are related to their battery, in terms of energy capacity, time to recharge, weight and cost. One of the most important consequences is a limitation in driving range, which especially impacts commercial vehicles. Therefore in order to plan routes for this kind of vehicle, it is necessary to precisely estimate the energy required to drive and plan for charging whenever needed. This paper introduces the Two-stage Electric Vehicle Routing Problem (2sEVRP) that considers detailed information about the paths when estimating energy consumption and planning the routes. First, a method to calculate cost parameters for the road network is outlined including topography, speed, powertrain efficiency and the effect of acceleration and braking at traffic lights and intersections. Second, an integrated two-stage approach is described, which finds the best paths between pairs of nodes and then finds the best routes including battery and time-window constraints. Energy consumption is used as cost function including payload and auxiliary systems. The road cost parameters are aggregated to generate the path cost parameters that are used in the routing problem. In this way all the details of the paths are taken into account when computing energy demand for the routes. Last, numerical experiments were conducted with the road network from Gothenburg-Sweden and high-fidelity vehicle model simulations, focusing on trucks for urban distribution of goods. The results indicate that time and energy estimation are signeficantly more precise than existing methods. Consequently it is possible to generate important savings and be sure that the planned routes are feasible.