A drone-assisted last-mile delivery framework for shipment prioritization in post-disaster and high demand periods

The aftermath of a disaster can observe increased demands for online purchases and deliveries due to a decreased local supply. The increased demands may then induce delays in item delivery. Natural disasters may also result in epidemics and critical medical situations. Thus, the deliveries can include both life-essential items, such as medicine or medical equipment, and non-essential items, such as toys or decor products. Similar circumstances may be induced by other abnormal situations, such as pandemics or wars. It is then important to prioritize shipments to ensure early delivery of life-essential products at the expense of delaying non-essential items. In this work, we introduce a framework to prioritize shipments with application on drone-assisted last-mile deliveries. While the framework is general and can be used in different last-mile delivery types, the selection of drone-assisted deliveries is important for post-disaster situations to allow for contactless deliveries in case of epidemic outbreaks, and to reach destinations inaccessible by vehicles due to damaged roads and infrastructure. We consider different priority levels ranging from high priority to low priority items. High priority items must be delivered as soon as possible, medium priority items must be delivered within a certain time frame, and low priority items can be delivered after the high and medium priority conditions are met. We introduce a mixed integer program to model the drone-assisted last-mile deliveries with the prioritization scheme and propose a solution framework to systematically solve the problem. Finally, we illustrate the benefits of the model through numerical cases and simulations, and discuss its implications.