Bluetooth is a standard wire-replacement communications protocol primarily designed for low power consumption, with a short range (power-class-dependent) based on low-cost transceivers integrated into each device. Because the devices use a radio (broadcast) communications system, they do not have to be in full visual line of sight of each other. Bluetooth was designed for exchanging data over short distances (using short-wavelength radio transmissions in the ISM band from 2400–2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Bluetooth uses a radio technology called frequency-hopping spread spectrum, which chops up the data being sent and transmits chunks of it on up to 79 bands.
There are currently over 30,000 members in the Bluetooth SIG, with Bluetooth included in over 90% of all mobile phones shipped. More than 3 billion new devices a year supporting Bluetooth are manufactured. Bluetooth has truly ubiquitous reach.
Bluetooth has been proven as a highly effective and cost-efficient means of determining travel time, speed, origin-destination and other valuable data points through Bluetooth probes identifying discoverable Bluetooth devices at multiple locations. This method has been researched in academic circles for years with the first reports coming out in 2008. Since that time research and validation has added to the robustness of the overall approach. From re-identifying the Bluetooth unique identifier (MAC) with a synchronized time stamp, longer periods of data can be collected than traditional license plate readers or floating car studies.
In order to most effectively collect Bluetooth data highly reliable field devices must be utilized. Similar to other wireless devices not all Bluetooth radios are created equal. In academic and commercial testing having a full power radio, as provided by BlueMAC devices, allows for higher volumes of data points with consistent captures and matched trips.
Collecting data with the intention of having data is a meaningless goal. Because of this and in conjunction with the best possible captures and matches, a dynamic and robust software suite must be utilized to ensure the data is used in a manner which reliably answers the questions being asked. The system begins with the obvious goal of providing ongoing and consistent travel time and speed data, while enabling additional questions to be answered through analytics. In BlueMAC’s years of experience with Bluetooth technology we have seen a desire from agencies worldwide to have access to dynamic origin-destination, path of travel, travel time reliability and a number of other aggregated data reports. By requiring more than standard travel time and speed data, our customers are ensured the ability to utilize the data being collected at the highest rate of return on investment.
Bluetooth as a technology has certain limitations that must be acknowledged. First and foremost, the technology is only getting a sampling of the roadway traffic. This sampling averages between 15% and 20% with the BlueMAC solution although we have seen sample rates as high as 50%+. Based on academic research, the commonly held rate to achieve valid data is 3-5% and anything higher increases confidence in the data. That being said no agency should expect the technology and its use in traffic data to be able to provide volumes or classifications without applying advanced statistical analysis algorithms. With regards to the BlueMAC system there are means to track intersection delay built into the system. The calculation method utilizes the BlueMAC system reporting all MAC address reads for all Bluetooth devices in range. Because of this our customers can look at the time from first seen to last seen and provide an intersection delay number. The one shortcoming of this method is that like all wireless technologies all barriers, even glass, limit the range of the device. Due to range variability the intersection delay reported numbers should be an estimated number – noting they are part of what our customers get built-in with BlueMAC. This is where utilizing Bluetooth in conjunction with other ITS solutions is key.