Improving the effectiveness of traffic monitoring based on wireless location technology.

A fundamental requirement for effectively monitoring and operating transportation facilities is reliable, accurate data on traffic flow. The current state of the practice is to use networks of point detectors to gather information on traffic flow at fixed points on the roadway network. Traffic monitoring based on wireless location technology (WLT) offers an opportunity to expand the size of the transportation network being monitored at a lower cost than with point detection. In WLT-based monitoring, the locations of individual wireless devices are sampled anonymously. By tracking a series of positions for devices in vehicles, it is theoretically possible to estimate the average travel speed on a road. Although the concept of WLT-based monitoring is attractive, results have been mixed. Field tests have been successful at locating vehicle positions but have not been able to generate traffic information of the quality or reliability required for most applications. This research explored how WLT-based monitoring could be improved by rigorously examining the problem from a system design perspective. The evaluation focused on two measures of effectiveness: (1) the availability of speed estimates and (2) the accuracy of speed estimates. The performance of WLT-based monitoring systems was evaluated through a combination of controlled testing on simple networks and case studies on simulated real-world networks. Significant main effects and interactions were evaluated in a systematic manner using a test bed that combined microscopic traffic simulation and a model of a WLT-based monitoring system. The results revealed several important issues to be considered when designing and implementing a WLT-based monitoring system. The selection of parameters such as the number of vehicles tracked and frequency between readings needs to be tailored to handle localized traffic and geometric conditions. The results showed that well-designed monitoring systems could produce accurate results although there were some situations where performance could be improved. Guidelines for the design and use of WLT-based systems were generated, and future avenues to improve system performance were noted.