POSITIONAL ACCURACY OF GLOBAL POSITIONING SYSTEM AND CELLULAR PHONE TRACKING FOR PROBE VEHICLES

The paper presents the evaluation results of two technologies, Global Positioning System (GPS) and cellular phone tracking for vehicle probes to collect traffic data. A custom software package was developed to conduct the technology evaluation. The software, the Travel Information Probe System (TIPS) maps positions of probes of arbitrary accuracy to an embedded geographic information system (GIS) to determine the path the probe vehicle took. Once the path has been determined, the software calculates the travel time for each road segment traversed. The simulation study of road data from two counties in the San Francisco Bay Area suggests that GPS and cellular technologies are capable of producing travel time information for nearly all roads. A technology with 20-meter accuracy can produce data for 99.2% of surface street segments and 98.9% of the freeway segments in the two counties studied. While low accuracy location technologies may not be suitable for freeway surveillance due to difficulties distinguishing between freeways and frontage roads, they may still be very effective for traffic surveillance on major surface streets