Travel Time Estimation on the San Francisco Bay Area Network Using Cellular Phones as Probes

Current traffic travel time estimates are largely based on road sensors embedded in the pavement. Today technical developments in cellular positioning and the spread of wireless phones provide the opportunity to track cell phone equipped drivers as traffic probes. The Federal Communication Commission Phase II mandate for Enhanced-911 (E-911) requires that wireless carriers must provide the location of a 911 wireless call by October 1, 2001 to the Public Safety Answering Point (PSAP), within approximately 125 meters, or under one-tenth of a mile in the majority of situations. The motivation of this research is to evaluate the feasibility of using cell phones as traffic probes for the Bay Area network. A review of cellular positioning techniques, an analytical model, as well as a simulation model show that accurate travel times estimates can be obtained. Assuming that at least 5% of freeways travelers are equipped with a cell phone, one can predict a 95% accuracy in freeway link travel time estimates. The E-911 mandate will be the driving force to implement such cellular positioning. However, the production, or adaptation, and warehousing of traffic information from the cell-phones-as-probes can be tailored for the requirements of traffic authorities and information service providers and may become an important business opportunity. The report also advocates the joint field evaluation of GPS, cellular and conventional systems, to allow the identification of the best mix of technology for future implementations. The possible institutional role of the PATH organization to foster a quicker deployment of these technologies in California is also presented in this report.