GRASP with a New Local Search Scheme for Vehicle Routing Problems with Time Windows

The NP-Hard Vehicle Routing Problem with Time Windows (VRPTW) is one of the major transportation problems. In this paper, a Greedy Randomized Adaptive Search Procedure (GRASP) for VRPTW is discussed for minimizing the fleet size and the travel distance. There are two phases within each GRASP iteration: construction phase and local search phase. In the construction phase, the initial solution is computed by applying an adaptive randomized greedy function. In the local search phase, the search procedure is applied to the constructed initial solution obtained by the construction phase for an improvement. In this paper, we propose an improved solution technique by using new local search ideas and new lower bounding procedures. In addition, we report computational results and address some practical issues in this area.