Commercial GPS-based travel time datasets have been acquired and a wide range of modeling-related uses for it both at the MPO and statewide levels within Ohio are being contemplated. These include model validation at corridor level, development of new “speed tables,” and buffer indexes for travel time reliability for estimating project benefits. The speed table development and validation of some MPO models previously has been accomplished with small-sample floating-car surveys.

Uses and potential pitfalls with these data to watch for will be presented, including problematic relationships to traffic volume and time of day, and the discovery of some “biased” values in the data for traffic modeling purposes when compared to other sources (spot speed monitoring sites as well as the floating car surveys). A more limited but continuing role for the traditional data sources is also recommended given such biases and limited GPS-based data available on some functional classes of roads.