An ant colony algorithm for the time-independent and time-dependent vehicle routing problem with time windows

Abstract

The Vehicle Routing Problem (VRP) determines a set of vehicle routes originating and terminating at a single depot such that all customers are visited exactly once and the total demand of the customers assigned to each route does not violate the capacity of the vehicle. The objective is to minimize the total distance traveled by all vehicles. An implicit primary objective is to use the least number of vehicles The Vehicle Routing Problem with Time Windows (VRPTW) is a variant of VRP in which lower and upper limits are imposed to the delivery time of each customer. The arrival at a customer outside the specified delivery times is either penalized (soft time windows) or strictly forbidden (hard time windows). In the time-dependent VRP, the travel times between the customers vary due to different traffic conditions in time intervals throughout the scheduling horizon beside different road types. In this thesis, both the time-independent and -dependent VRP with hard time windows are addressed. We tackle these problems using an Ant Colony Optimization approach. The performance of the proposed algorithm is tested on the well-known benchmark instances from the literature.