Time-varying travel times in vehicle routing

Models and algorithms for vehicle routing are usually based on known constant travel times between all relevant locations, an assumption that is far from reality, particularly for urban areas. But the consideration of travel times that vary with the time of day poses two serious problems: the adaptation of the algorithms and the procurement of reliable data about the behavior of the travel times in the road network. This article describes the derivation of travel time data from modern traffic information systems. It presents a general framework for the implementation of time-varying travel times in various vehicle-routing algorithms. Finally, it reports on computational tests with travel time data obtained from a traffic information system in the city of Berlin.