Field Operational Test Using Anonymous Cell Phone Tracking for Generating Traffic Information

Abstract

This paper presents some preliminary results from an on-going field operational test using anonymous tracking of cellular phones to generate traffic information. The test is being conducted in Tampa, Florida in cooperation with a major telecommunications carrier using location technology originally developed for locating emergency calls from cell phones. The location technology generates moderately accurate cell phone positions allowing the development of a traffic surveillance system that could generate travel information for all roads in a street network. Travel time measurements produced over a 24-hour period by the traffic monitoring system were archived and aggregated into 5-minute intervals. The percentage of roads monitored in each 5-minute interval was calculated. The numbers of measurements in each time period were compared to desired sample sizes for different degrees of accuracy and confidence. Over 24 hours, the traffic monitoring system produced measurements for 98.7% of all freeways and major surface streets in the study area. Between 10:00 am and 10:00 pm, the system produced data for an average of 76% of all the freeway miles in every 5-minute interval. With phones from a single carrier, the number of measurements was sufficient to generate average speeds accurate within 5 mph with 95% confidence for 38.1% of the freeways and within 10 mph with 95% confidence for 71.5% of the freeways in every 5-minute interval between 10:00 am and 10:00 pm. While the volume of measurements is sufficient for a good traffic monitoring system, further work is needed to empirically confirm the accuracy of the generated traffic data.