MODELING THE IMPACTS OF WEATHER AND DEMAND UNCERTAINTIES ON UAVS FLEETS AND EMISSIONS

Growing e-commerce volumes and consumer expectations of free and faster shipping are pushing the adoption of new delivery vehicles. New driverless air and ground vehicles are being launched and tested to deliver products or services by traditional package delivery companies or to support innovative ideas in retail, groceries, and healthcare. For the delivery of time-sensitive supplies, drones may provide the means to bypass many obstacles experienced by ground transportation vehicles. However, drones are subject to their own set of constraints, like weather conditions and limited range, that limit the likelihood of successful deliveries. Drones are increasingly being utilized to deliver medical supplies, and the COVID-19 pandemic has accelerated this trend. Drones arrive quickly by taking more direct paths and avoiding ground-based obstructions. However, drones are not completely reliable and may also experience failures and delays. For consumer products, delivery delays are an inconvenience, but for some time-sensitive deliveries like medical supplies delays are likely to cause severe health impacts or even fatalities. The number of drones needed when there is demand uncertainty is highly dependent on charge times, use of battery swapping, and population in the service area. Additional consideration should also be given to potential mechanical failures and maintenance schedules. It is important to note that failures due to extreme weather conditions cannot be addressed by simply having more available drones. Extreme weather conditions, which will result in a failed delivery for one drone, will result in a failed delivery for any other drone because drones cannot operate under extreme weather conditions. Wind is a key constraint for drone deliveries. Successful drone deliveries are highly influenced by wind speeds, wind direction, and precipitation rates; however, the ambient temperature may mostly be ignored for short delivery distances. Furthermore, there is an access and equity question associated with a drone’s ability to deliver to some areas. For example, airports are often restricted flight zones that allow for no drone operations. Such areas are also areas with higher proportions of lower-income communities. Future research could examine where a delivery system could be employed and what ground delivery systems are required locally to adjust for access differences. Another important aspect is the sustainability of drone deliveries. In terms of energy and emissions efficiency there is no vehicle type that dominates across the board. Drones are more efficient in time constrained and low-density delivery scenarios. Road autonomous delivery robots (RADRs) are more efficient than E-vans when delivering to relatively low number of customers. New air and ground autonomous vehicle types may reduce carbon emissions significantly but they may not necessarily reduce on-road travel. For some autonomous vehicles the reduction of on-road travel is also accompanied by additional travel on sidewalks (SADRs) or air travel (drones). In summary, drones or Unmanned Aerial Vehicles (UAVs) can significantly improve the reliability of time-sensitive deliveries in urban and rural areas as well as reducing carbon emissions. Policy makers and regulators should seriously consider their benefits as well as potential safety risks related to malfunction or mid-air collision