Air Risk Maps for Unmanned Aircraft in Urban Environments

The increasing use of Unmanned Aircraft Systems (UAS) over inhabited areas requires the use of a suitable risk assessment. In this paper, we propose the use of air risk maps to assess the risk to people caused by mid-air collision accidents during a UAS flight operation. The proposed risk assessment tool is based on a state-of-the-art mathematical model for determining the rate of mid-air collisions of an unmanned aircraft with general aviation (GA). To evaluate the growing traffic of unmanned aircraft (UA), the model is also exploited to estimate the rate of mid-air collisions with other unmanned aircraft operating in the same airspace. The resulting rate of mid-air collisions is used to estimate the expected frequency of fatalities following mid-air collision accidents, here denoted as air risk. The air risk is computed using a probabilistic approach estimating the number of people involved in the accident, as well as the probability of fatality. Specifically, the air risk is computed for each geo-referenced element of the air risk map by combining several layers, including the population density and sheltering factor, as well as the physical parameters of the aircraft. The proposed risk assessment tool is applied considering the Italian airspace, evaluating both the GA and UA traffic. Further analysis is also conducted to evaluate a future scenario with an increased number of UAS, observing a not negligible air risk.