Project Details

Free flow speed (FFS) is used as an input for many key performance measures, such as travel time reliability and congestion measures for interstates and arterials. While traffic practitioners generally agree on the idea that FFS should be estimated under good weather conditions and without incidents, some studies suggest that driver behavior is always in a compromised status under the influence of both internal and external conditions. FFS calculated using different methods can yield varied, inconsistent results. In response to VDOT operational needs, it is imperative to develop consistent free flow speed estimation methods for performance measures. In response, this project will develop a set of methodologies to (1) compare commonly available FFS estimation methods on interstates, (2) evaluate how FFS estimates affect performance measurements on the interstate network, and (3) explore the usage of probe data for arterial FFS estimation.