Scheduling last-mile deliveries with truck-based autonomous robots

To reduce the negative impact of excessive traffic in large urban areas, many innovative concepts for intelligent transportation of people and freight have recently been developed. One of these concepts relies on autonomous delivery robots launched from trucks. A truck loads the freight dedicated to a set of customers in a central depot and moves into the city center. Also on board are small autonomous robots which each can be loaded with the freight dedicated to a single customer and launched from the truck. Then, the autonomous robots move to their dedicated customers and, after delivery, autonomously return to some robot depot in the city center. The truck can replenish robots at these decentralized depots to launch further of them until all its customers are supplied. To assess the potential of this innovative concept, this paper develops scheduling procedures which determine the truck route along robot depots and drop-off points where robots are launched, such that the weighted number of late customer deliveries is minimized. We formulate the resulting scheduling problem, investigate computational complexity, and develop suited solution methods. Furthermore, we benchmark the truck-based robot delivery concept with conventional attended home delivery by truck to assess the potential of this novel last-mile concept.