Wireless Location Technology–Based Traffic Monitoring: Preliminary Recommendations to Transportation Agencies Based on Synthesis of Experience and Simulation Results

There has been a growing interest in using anonymous tracking of wireless devices as a way to generate travel time and operational data cost-effectively. Unfortunately, there are relatively few independent quantitative evaluations of these systems. Evaluations that do exist are often not widely available, so agencies often enter into deployment agreements with a limited understanding of the abilities and limitations of this technology. This paper provides an overview of the results of past deployments of wireless probe monitoring systems. It also discusses a simulation study of the predominant type of system on the market today, handoff-based monitoring systems. Past deployments show that early-generation systems encountered significant problems in generating accurate speed estimates. More recent tests using handoff-based technology have shown improvement in data quality at some sites, but there are not enough data to characterize fully whether those systems can consistently provide useful operational data. The simulation study indicates that the way in which the cellular network topology overlays the roadway network could be a critical determinant of overall system effectiveness. Simulation results indicate that often with simulated handoff-based systems speeds can be estimated to within 5 mph.