Investigation of Bluetooth-Based Travel Time Estimation Error on a Short Corridor

摘要

Travel time data have been notoriously difficult to collect. Although recent advances have madethe task easier with license plate matching, toll tag data and aggregate GPS data from privatevendors, many entities seek to further simplify the task by exploiting short range communicationprotocols, such as Bluetooth. Bluetooth travel time estimates are now being considered to feed avariety of applications, such as user information systems. As Bluetooth-based travel time datacollection increases in popularity, investigating the errors that are characteristic of this detectiontype becomes more important. The issue of error on short corridors in particular is of interest, asthe “zone to zone” nature of Bluetooth sensors implies that shorter corridors will have greatertravel time errors. This study tests nine varying configurations of Bluetooth detectors on a 0.98mile long segment. Three types of antennae and three different sensor arrangements are tested todetermine the effects of these variables on travel time error.The collected travel time data is compared to license plate reader data, which, due to itsrelatively small, vehicle-only, detection zone is taken as the ground truth travel time. The resultssuggest that a larger detection zone is desirable, despite the apparent loss of accuracy, as thehigher matching rates obtained by the system will improve sample size and reduce random errorrates. A pair of Bluetooth detectors mounted on opposing sides of the roadway, (with a 7dBiantenna on one and a 9dBi antenna on the other) at each end of the corridor resulted in thesignificantly less error than other combinations of mounting locations and antennae. Findings ofthis study are helpful to transportation professionals attempting to understand the errorsassociated with the Bluetooth-based travel time data collection technology and configure thesensors to mitigate the errors.