The Passive Final Approach Spacing Tool (pFAST) Human Factors Operational Assessment Katharine K. Lee, and Beverly D. Sanford Abstract Decision-support tools to assist air traffic controllers in the current terminal and en-route air traffic environments have been developed at NASA Ames Research Center in conjunction with the Federal Aviation Administration. These decision-support tools, known collectively as the Center-TRACON Automation System (CTAS), provide decision-making assistance to air traffic controllers through computer-generated advisories. One of the CTAS tools developed specifically to assist terminal-area air traffic controllers is the Passive Final Approach Spacing Tool (pFAST), which has been tested extensively in simulation and operationally. In 1996, pFAST underwent an operational assessment at the Dallas/Ft. Worth, Texas, Terminal Radar Approach Control (TRACON) facility. Engineering results showed an increase in throughput and runway balancing efficiency. Human factors data collected during the operational assessment showed that controller self-reported workload was not significantly increased or reduced by pFAST. Rather, controllers reported that the levels of workload remained largely the same. However, significant differences in the nature of controller coordination and communication were identified. Controller ratings indicated that pFAST was acceptable. This report describes the human factors data that were collected during the 1996 pFAST Operational Field Assessment and describes the controller-reported levels of acceptance, usability, and suitability in the operational environment. An emphasis on the effects of pFAST on the coordination and communication between the controllers is provided. The lessons learned from the perspective of human factors in the field testing process are also discussed, along with comments on the development of future air traffic control automation.