Influence of Vertical Sensor Placement on Data Collection Efficiency from Bluetooth MAC Address Collection Devices

The consumer electronics industry has made extensive use of the Bluetooth wireless protocol in many portable devices. A substantial number of these Bluetooth devices broadcast a unique identifier in the form of the media access control (MAC) addresses. These MAC addresses can be captured electronically and the same matching algorithms used in traditional license plate studies can be used to estimate segment travel time and origin-destination matrices. This paper briefly illustrates how these data can be used to estimate arterial link travel times and empirically illustrates the sensitivity of sample size to sensor placement. A controlled experiment with fixed lateral mounting and varying vertical mounting heights is then conducted to develop design recommendations for mounting Bluetooth monitoring devices. The paper concludes by recommending a Class I Bluetooth detector mounting height of at least 8 ft above the pavement grade. Based on a 24-h empirical data set on I-65 in Indianapolis, we found that 7.4% of the vehicles within 30' and 6.6% of the vehicles between 102' and 114' had a discoverable MAC address.