We discuss the design and implementation of Traffic Reporter, a PC-based, graphical, interactive, real-time, advanced traveler information system created to meet the information needs of Puget Sound area commuters. Traffic Reporter's goal is to influence commuter behavior and decision making so as to improve the efficiency with which commuters use available transportation facilities.This project began by studying commuter behavior and traffic needs in the Puget Sound area. We conducted extensive on-road surveys of Seattle motorists, with smaller, in-depth follow-up surveys. We identified four types of commuters, three of which are likely to respond to various types of traveler information. We then used this understanding of commuter behavior to design and develop a working prototype of Traffic Reporter.This paper describes the design and development of Traffic Reporter, how the current system works, and plans for future development.