The goal of this thesis is to improve pilot understanding of the Traffic alert and Collision Avoidance System (TCAS) by changing the Traffic Situation Display (TSD). This is supported by two objectives. The first objective is to create an integrated, realistic air traffic environment. This serves as an experimental platform for testing and evaluating future TCAS TSDs. The simulator environment includes a desktop flight simulator, background air traffic simulator, and intruder aircraft. The intruder aircraft uses seven dimensional waypoints to robustly follow trajectories and cause specific resolution advisories. Second, the relative benefits of, and potential concerns with, new TCAS TSDs are explored using a structured, iterative design process with subject matter ex- perts (SMEs). Incremental changes to the TSD were implemented into the simulator environment. SMEs evaluated the displays and potential points of confusion were identified. Several display features are discussed and implemented for future evaluations. These include boundary lines of TCAS variables depicted on the TSD and on a vertical situation display, speed lines which vary with the TCAS estimate of time to closest point of approach, and a prediction of the safe altitude target during a resolution advisory. Scenarios which may be confusing or misleading are discussed. These scenarios may be ameliorated or exacerbated by display features. This information is useful to guide both design and certification or operational approval and is a starting place for future TCAS experiments.