Accuracy of Travel Time Estimation Using Bluetooth Technology: Case Study Limfjord Tunnel Aalborg

Bluetooth Technology (BT) has been used as a relatively new cost-effective measurement tool for travel time. However, due to low sampling rate of BT compared to other sensor technologies, the presence of outliers may significantly affect the accuracy and reliability of travel time estimates obtained using BT. In this study, the concept of outliers and their impact on travel time accuracy are discussed. Four different estimators, namely Min-BT, Max-BT, Med-BT and Avg-BT, were used to estimate travel times using BT. By means of various estimation methods, it is tried to evaluate the impact of estimation method on the accuracy of estimated travel time using BT. Two sources of Floating Car Data (FCD) were used as the ground truth in order to quantify and evaluate the accuracy of travel time profiles obtained by BT. Three aggregation techniques including arithmetic mean, geometric mean and harmonic mean were used to construct the travel time profile using BT dataset. In order to quantify the impact of sample size on accuracy of travel time estimates, a series of sensitivity analyses are conducted. Results show that Min-BT and Med-BT are more robust in the presence of outliers in the dataset and can provide more accurate travel time estimates compared to Max-BT and Avg-BT. Moreover, implementing harmonic mean and geometric mean for travel time profile construction could significantly improve the accuracy of estimates obtained by BT.