Assessing URET Benefits for Airspace Users: A Quasi-Experimental Approach

Air traffic control organizations around the world are trying to develop automation tools to help controllers manage increasing workload and to enable user preferred routes. This paper focuses on such a tool: User Request Evaluation Tool (URET), which is a decision-support tool for en-route controllers. URET is a prototype of an automated conflict probe. Based on flight plans and actual radar tracks, the URET system models aircraft trajectories and predicts possible conflicts. It also enables controllers to check clearances for conflicts prior to their issuance. This tool is intended as a strategic decision-support tool for the D-side controller. When implemented in the Air traffic control system, tools like URET can affect many aspects of system performance, from controller workload, to safety, to the quality of service provided to users. The purpose of this paper is to determine the impact of URET on users--more specifically on flight times experienced by users. To do so, we employ statistical methods that compare changes in flight times before and after URET implementation for two sets of flights. One set includes flights that traverse the airspace where URET is implemented; the other includes flights that do not use that airspace. Results suggest that URET reduces flight times for flights using the URET airspace. Departure delay, rather than airborne time, is the flight time component that is most strongly affected, with a decrease of 0.5-3 minutes per flight depending on the analysis approach and time period analyzed. Airborne time reductions are in the range of 0.2-0.5 minutes per flight under one analysis approach, and statistically insignificant under the other approach. These results imply that much of the benefit from URET is non-local and derives from mechanisms other than more direct routing through URET airspace, which has been the focus of most earlier benefits studies.