Conflict probability based strategic conflict resolution for UAS traffic management considering Reasonable-Time-To-Act principle

This paper introduces a strategic conflict resolution method for Unmanned Aircraft System Traffic Management (UTM) that incorporates conflict probability estimation. The method discusses a two-step conflict detection process and three conflict resolution approaches: First-Come First-Served (FCFS), Reasonable Time To Act (RTTA), and an optimisation technique. The conflict detection process begins with coarse screening, which identifies intersecting Operational Volumes (OV) with potential conflicts, followed by precise conflict probability estimation. Intersections exceeding the predefined probability threshold from safety perspective are classified as conflicts, while others are deemed acceptable. By reallocating take-off time slot, the conflict resolution approaches have different priorities: the FCFS method adheres to traditional practices, the RTTA concept prioritises fairness, and the optimisation technique enhances efficiency. Numerical experiments are conducted in three-dimensional airspace environment under varying traffic densities. Six representative case studies linked by two threads, i.e., efficiency and fairness, thoroughly assess the proposed methods. Results indicate that integrating conflict probability significantly reduces delays, and further reductions can be achieved through the optimisation technique. The fairness issue inherit in the FCFS rule for flight processing is effectively addressed through the implementation of the RTTA principle.