We developed a microcomputer software package for analyzing and developing evacuation plans around nuclear power stations, the transportation evacuation decision support system—TEDSS. It is designed to help emergency managers make decisions in evacuation planning and operations. The system helps the user prepare detailed evacuation master plans for different scenarios, including evacuation times, best routes, expected traffic bottlenecks, and the allocation of evacuees to different shelters. In an actual emergency, the system helps the user to make decisions as the nature of the disaster changes, such as selecting proper zones to evacuate, estimating evacuation times, and providing routing strategies for the particular emergency. TEDSS has a knowledge base that contains the evacuation expert rules, disaster-related information, and an inference engine, which is a sophisticated simulation model. TEDSS employs graphic displays and system control capabilities to keep it user-friendly, flexible, quick to maintain, and easy to expand and modify.