Houston TranStar, which has been collecting travel time and segment speed data using vehicle probe data since 1995, has an extensive coverage area that envelops most local commuters' daily freeway routes. However, expanding the existing Automated Vehicle Identification (AVI) system would be cost-prohibitive except for high-volume freeways. The partners of the Houston TranStar consortium needed a new method to measure speeds and travel times on arterial roadway systems and rural freeways. Instead of using co