You might be familiar with the name Bluetooth® as a way of wirelessly talking on your cell phone. More generally, it’s a personal area network that connects devices wirelessly over short distances.
Researchers at the Texas Transportation Institute (TTI) are using Bluetooth technology for a host of applications involving traveler information, traffic management and planning systems. Currently these data are collected using toll tags, GPS, license plate recognition and cellular phone networks, which can be expensive and inefficient. Data collection by Bluetooth presents a viable alternative.
How the Technology Works
Each Bluetooth device has a unique identifier called a Media Access Control (MAC) address, which the device transmits within a short range.
“A motorist with a Bluetooth-enabled device drives by a road sensor, and the sensor reads the MAC address,” says Darryl Puckett, a TTI research scientist investigating uses of Bluetooth technology. “Further down the road, another sensor reads the MAC address again, and the system matches it to the first reading.” Software then determines how long it took to travel from one reader to the other and calculates the average speed.
Privacy is an important concern. MAC addresses are not directly associated with a specific user and do not contain any personal information. Users can also disable the Bluetooth function of their device to prevent it from being read.
The benefits of this anonymous wireless address matching (AWAM) system are many. A large percentage of the population has Bluetooth devices, so the technology is easy and nonintrusive for motorists. The roadside readers are low cost and low maintenance, using standards-based, non-proprietary equipment and protocols.
Applying the Technology
Funding from the University Transportation Center for Mobility (UTCM) assisted TTI researchers in developing a full, end-to-end solution for AWAM, with the following features:
- roadside hardware and software for reading and forwarding MAC addresses,
- host software for calculating real-time and historical travel time and speed data, and
- analysis and graphics capability to view current and historical data graphically.
Millions of motorists cross the U.S.-Mexico border every day, often with long delays. Current methods of determining delay — usually by visual estimates or motorist survey — are unreliable.
“Deployment of Bluetooth technology at the border is geared toward obtaining crossing times of passenger vehicles, which can then be used to accurately estimate wait times,” says Rajat Rajbhandari, TTI associate research engineer. “This project was the first of its kind to use Bluetooth technology to gather traffic information in Texas.”
Researchers collected data at three ports of entry in the El Paso, Texas, region: the Bridge of the Americas, Ysleta and Paso Del Norte. The study confirmed that Bluetooth technology could be used to measure U.S.-Mexico border crossing times. A follow-up project will deploy Bluetooth sensors at the Ysleta port of entry in El Paso and compute the crossing time in near real time.
“We’re also working on deployment of RFID [radio frequency identification] technology at border crossings in El Paso, Laredo, Pharr and Arizona to get crossing times of commercial vehicles,” says Rajbhandari. “Crossing time information for both passenger and commercial vehicles is crucial to understand the operational and planning aspects of international border crossings.”
Travel time data can help commuters choose when and what route to travel and help planners identify congested segments for operational or infrastructure improvements. TTI has worked on several projects in Texas:
- Houston commuters can check the TransStar website to see how long it will take to get to work. The partnership between Houston TranStar and TTI is investigating whether AWAM can expand this coverage to arterials.
- AWAM proof-of-concept demonstrations with the City of Houston, the Texas Department of Transportation (TxDOT) and Harris County on urban arterials showed that Bluetooth device penetration is sufficient to collect high-quality travel time data.
- In a project for TxDOT, TTI collected travel times and speeds on identical roadway segments using a toll tag reader system and the AWAM system, with comparable results.
- TTI has deployed the AWAM system at several west Houston intersections to monitor travel time for a network of urban arterials.
- TTI demonstrated the AWAM system on parallel routes to U.S. 75 North Central Expressway between Dallas and Richardson.
“I see this technology as an exciting, innovative way to obtain traffic information in places where we would not otherwise be able to gather data because of the cost,” says David Fink, a TxDOT transportation operations engineer with Houston TranStar. “Other technologies can be up to eight times more expensive than using Bluetooth technology. In some cases this is just cost-prohibitive.”