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RFID Readers Installed at U.S.-Mexican Bridges to Help Ease Traffic Congestion

To better measure traffic flow, the Texas Transportation Institute and private R&D organization Battelle have installed a system that reads government-issued passive UHF tags attached to the windshields of northbound commercial traffic.
By Claire Swedberg
According to Rajbhandari, between 50 and 80 percent of trucks passing through the borders are equipped with some type of RFID transponder. The tags have a variety of purposes and origins. As part of the Free and Secure Trade (FAST) program, for example, some freight carriers attach TransCore's eGo passive ultrahigh-frequency (UHF) transponders to their trucks' windshields. The tags, provided by CBP, comply with multiple air-interface protocols, including the American Trucking Associations (ATA) protocol. Similarly, the Texas Department of Public Safety (DPS) is using the passive eGo tags to help identify the trucks passing through its safety-inspection facility.

Thus, in 2007, TTI and Battelle offered Texas DOT a solution using those existing transponders for tracking traffic movement across the BOTA, in order to measure and store data about crossing times for commercial vehicles.


Rajat Rajbhandari, a TTI research engineer
By leveraging the existing vehicle transponders, Rajbhandari determined that a system could be put in place without requiring anything on the part of those traveling across the borders (such as acquiring tags). The research team installed TransCore's Encompass 4 passive UHF RFID readers to capture the unique identifiers of those transponders at two locations. The first reader was installed at a point located approximately 1.5 miles before U.S.-bound trucks reach the Mexican inspection station, where drivers' paperwork is examined by Mexican officers. In this case, the interrogator's location is intended to capture the "worst-case scenario"—that is, the point at which traffic may begin to slow during the heaviest congestion. The second reader location was installed after two inspection processes in Texas (first by CBP, to inspect for unauthorized cargo, and then by DPS, to ensure that each truck meets road-safety requirements). In that way, readers could capture the time it took the vehicle to travel from 1.5 miles prior to the first inspection site, in Mexico, through the final inspection location in the United States.

Readers were installed at the two locations in 2009, each wired to three antennas installed above three lanes. As a vehicle with a TransCore eGo passive tag passes under the reader antenna (active RFID tags, such as those used by some types of toll transponders, can not be read by this system), the reader captures the tag's unique identifier, links it with a timestamp and location data, and then forwards that information to software designed by TTI, residing on a server dedicated for this purpose. In the software, the tag ID numbers are stored anonymously—that is, they are not linked to the identity of the driver or trucking company. When the tag passes the second reader—on the U.S. side of the border, at the point at which trucks exit the inspection station run by DPS—the length of time that has passed since the first read is calculated in the software for that ID number. The software then determines an average crossing time every 15 minutes, based on the travel time of all vehicle transponders, and that data is transmitted to the back-end server via a GPRS cellular connection, and stored there.

The system became operational in July 2009. In August 2010, with additional funding from FHWA and with CBP's approval, TTI and Battelle installed an additional reader at CBP's primary inspection facility, at the same crossing, in order to provide more granular data indicating how long the trucks had to wait after completing the Mexican inspection process, with the reader capturing transponders' IDs as trucks arrived to pass through CBP inspection booths.

The system reads between 600 and 1,000 transponders daily. In most cases, the tags are read at all three locations. In some cases, however, one read might be missed—typically because a vehicle is moving too quickly—in which case, the information is discarded.

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