Developing Twin Cities Arterial Mobility Performance Measures Using GPS Speed Data

The overall goal of this study was to use commercially-available travel speed data to develop arterial street mobility performance measures in the eight-county Twin Cities Metropolitan Area. The research team licensed 2011 historical traffic speed data from INRIX for 1,604 directional-miles of arterial streets, and conflated this speed data with MnDOT traffic volume data on the same street network. Based on prevailing practice, TTI recommended travel speed-based mobility performance measures that compare peak traffic speeds to speeds during light daytime traffic. However, it was recognized that light daytime traffic speeds are not necessarily the goal or target for the performance measures, but simply a convenient and easily-measured reference point. Instead, performance measure target values should be context-sensitive and based upon surrounding land use. Multiple measures should be used to quantify and monitor mobility on arterial streets, including delay per mile, travel time index, and the planning time index (a measure of reliability). The exact mobility performance measures and target values are likely to evolve and be refined as MnDOT and partner agencies gain experience in performance monitoring on arterial streets. At this time, TTI recommends calculating, tracking, and gaining experience with multiple measures, while also determining where these measures can be used to improve agency decisions.