Optimizing synchronized truck-drone delivery with priority in disaster relief

Rapid delivery of emergency supplies is of vital importance in disaster relief, and innovative means of delivery has been actively explored. Recently, a novel delivery approach that takes advantage of both trucks and drones is emerging in the commercial field. This synchronized truck-drone delivery (STDD) mode can benefit from the large capacity of trucks as well as the speed and flexibility of drones, which makes it promising for sending ungently-needed supplies to disaster-stricken sites, especially the areas severely damaged and thus inaccessible by trucks. This paper attempts to optimize the synchronized truck-drone paths for quick responses in disaster relief, when accounting for the priority of different disaster-stricken sites. We propose an integer programming model and develop exact algorithm to solve small-scale problems. For large-scale problems, we propose an algorithm based on dynamic programming. We verify that the STDD mode is more efficient than truck-only delivery. Further numerical analysis suggests that a drone with higher speed and longer endurance is not always the best choice. The efficiency of rescue efforts relies on careful calibration of the speed ratio of the drone to the truck and the maximum flight distance of the drone. Finally, the application of the model is illustrated by a case study of the 2008 earthquake at Wenchuan County in Sichuan Province of China.