Collision risk assessment between aircraft and obstacles in the areas surrounding airports.

The topographical features of a site and the anthropogenic artefacts inside and outside the airport boundaries influence the infrastructure use. Objects penetrating the obstacle limitation surfaces (OLS) or standing outside those surfaces have to be mapped and risk-assessed because they could be a hazard to air navigation. This study aims to quantify the risk of collision between aircraft and obstacles in the airspace. There are no available procedures in the literature: the authors supposed that the obstacle type and the examined OLS affect the collision risk. The proposed risk values and amplification factors derive from interviews with technicians. The methodology has been implemented in an existing airport with 589 penetrating obstacles: the results highlight that 69.8% of obstacles imply a negligible risk, and 3.7% require further analyses by the competent aviation authority. In this study, buildings and pylons penetrating the Transitional Surface are the most hazardous obstacles.