A drone fleet model for last-mile distribution in disaster relief operations

facilities, the disruption of health systems and the breakdown of already on-going treatments in case of emergency. Contaminated water and poor sanitation conditions combined with low vaccination coverage often leads to water, air- and vector borne diseases, e.g. cholera, hepatitis or malaria, as it was observable in the diarrhoea outbreak in the Cup of Horn crisis in 2011. In addition to these circumstances, aid agencies are often confronted with poor or inexistent infrastructure that is further disrupted in case of disasters. As the supply via trucks and helicopters is not applicable in these regions, alternative means of transport have to be taken into consideration. Unmanned aerial vehicles (UAVs), or drones, are receiving increased attention by humanitarian organizations as they can support overcoming last-mile distribution problems, i.e. inaccessibility to cut-off regions. This paper considers drone application in last-mile distribution in humanitarian logistics and presents an optimization model focusing the delivery of multiple packages of lightweight relief items (e.g. vaccine, ready-to-use therapeutic food packages, etc.) via drones to a certain number of remote locations within a disaster prone area. The objective of the model is to minimize the total traveling distance (or time/cost) of the drone under capacity and energy constraints while recharging stations are installed to allow the extension of the operating distance of the drone. Different priority policies could also be implemented. The model is solved as an integer linear program and illustrated with different scenarios.