If the often-predicted increases in demand for air transportation materializes, there is every indication that the traffic handling capacities of many of today's airports will have to be increased to meet the demand and reduce airfield congestion. One method that has been suggested by airport planners is the design of high speed exit taxiways in airports. However, within the past five years, particular interest has been raised about the performance of these exits. Redesign of the exits or new proposals have been called for. This thesis investigates the level of performance of high speed exit taxiways in two Canadian airports. It examines the various factors that may contribute to deter from the best performance and makes recommendations about necessary changes. Results of data collected show that pilots may be overestimating their speeds on the exits. It was also found that pilot's deceleration on the runway follows a non-uniform profile. This means that pilot behavior is similar to automobile drivers who reduce their speeds near highway exits in order to shoot for the exits at their anticipated speeds. It also appears that existing high speed exits may be about 30 - 60% effective, because observed speeds lie between 30 - 45 mph. A model is developed which will help in evaluating high speed exits in existing airports. The model is also used to develop new design principles for exit transition and circular curves. The new design principles incorporate speed-changing and turning movements into the transition curve. It also makes use of superelevation on the curves.