Improving The Accuracy Of Bluetooth Based Travel Time Estimation Using Low-Level Sensor Data

Bluetooth sensors have a large detection zone compared to other static Vehicle Re-Identification Systems (VRIS). Although a larger detection zone increases the probability of detecting a Bluetooth-enabled device in a fast-moving vehicle, it increases the probability of multiple detection events triggered by a single device. This could lead to location ambiguity and reduced accuracy of travel time estimation. Therefore, the accuracy of travel time estimations by Bluetooth Technology (BT) depends upon how location ambiguity is handled by the estimation method. The issue of multiple detection events in the context of travel time estimation by BT has been considered by various researchers. However, treatment of this issue has remained simplistic so far. Most previous studies simply used the first detection event (Enter-Enter) as the best estimate. No systematic analysis for exploring the most accurate method of estimating travel time using multiple detection events has been conducted. In this study different aspects of BT detection zone, including size and its impact on the accuracy of travel time estimation, are discussed. Moreover, four alternative methods are applied; namely, Enter-Enter, Leave-Leave, Peak-Peak and Combined to estimate travel time. These methods were developed based upon various technical considerations related to multiple detection events. A controlled field experiment was conducted to evaluate the accuracy of alternative methods through comparison with the ground truth travel-time data measured by GPS. Results show that the accuracy of Combined and Peak-Peak methods are higher than others and employment of first detection-event does not necessarily yield the best travel time estimation.