Virtual speed sensors using transit vehicles as traffic probes

In this paper, we present algorithms that use transit vehicles as probes for determining traffic speeds along freeways and other primary arterials. We describe a system of "virtual" probe sensors that measure transit vehicle speeds using automatic vehicle location system (AVL) tracking data. Examples showing the correlation between probe data and inductance loop spend trap data are presented. In addition, virtual sensor data, produced using transit vehicles as probes, is compared with inductance loop speeds during incidents identified in the DOT incident log. These comparisons demonstrate the effectiveness of virtual sensors based on using transit vehicles as traffic probes.