<title>Vehicle-based versus fixed-location measurements for traffic surveillance in IVHS</title>

Abstract

Many recent IVHS deployments feature vehicle probes as prominent sources of information about traffic conditions either in addition to or in place of traditional fixed location measurement devices such as inductive loop detectors. A number of other technologies now being considered for traffic surveillance that are deployed in fixed locations are reviewed and are found to provide the same kinds of information as more complex probe vehicle data collection systems. Recent experience with both fixed location and vehicle-based incident detection systems is summarized. Several incident detection algorithms calibrated with both fixed location and vehicle-based traffic measurements from a simulation of a signalized arterial street for a soon to be launched IVHS demonstration are introduced. The performance of these algorithms, some of which use data from only one source while others use data from both sources, is compared. While the fixed location measurements appear to be superior to the probe reports for detecting incidents when used alone, incidents detected by the respective algorithms do not completely overlap. Algorithms using both sources of data perform substantially better than either single-source algorithm, indicating that there is value in collecting information using both methods.