Optimal Method of Information Collection Cycle for GPS-Equipped Probe Car

The Global Positioning System (GPS) equipped probe car is now widely used as a new traffic information mobile detector. It has the advantages of high accuracy, wide coverage, and real time. Most of the former research focuses on optimization of map matching or collection cycle for a single vehicle. Yet, the influence of probe car sample size on collection cycle is rarely discussed. This paper provides an optimal method of collection cycle based on certain sample size. Travel time is used as the optimal parameter. By calculating the average absolute relative errors of individual link travel time (ILTT), a reasonable collection cycle range of a single vehicle is determined. Then, the relationship of sample size, collection cycle, and road coverage rate is discussed, and the sample size under the required road coverage rate can be obtained. Finally, using daily probe car data in Chengdu as an example, on the basis of reasonable collection cycle range for a single vehicle, the optimized collection cycle is determined according to the existing sample size.