Colorado to add transponder-tracking technology to I-70

| 6/26/2006

The state of Colorado is planning to launch a traffic advisory system that will use motorists’ toll transponder information.

The program will estimate travel times on Interstate 70 between State Highway 470 and Copper Mountain, and will broadcast announcements via electronic signs located every 15 miles along the roadway, the Denver Post reported.

CDOT Spokeswoman Stacey Stegman told the Post that the system is not capable of collecting personal information or monitoring speeders, and that the system’s private data is dumped from the system every two hours.

Colorado isn’t the first state to use transponder info. to monitor traffic flow.

On May 30, the San Francisco Bay Area’s Metropolitan Transportation Commission and the California Department of Transportation announced that the traffic information Web site,, would begin using up-to-the-minute traffic information on State Routes 1 and 92 between Half Moon Bay and the Interstate 280 junction.

The program’s traffic information network was launched in March 2004 on Interstates 80, 680 and 880, and has been expanded several times since. With the addition of State Routes 1 and 92, the network now includes the entire length of Interstates 280, 580, 680, 780, 880, 980 and 238; and State Routes 13, 24, 37, 85, 87 and 242; as well as extensive coverage of Interstate 80, U.S. 101, and State Routes 4, 17, 84 and 237.

The Web site bases its traffic information on three systems, one of which is the monitoring of toll transponders passing through special roadside electronic readers, which then calculate the speed at which the vehicle was traveling and average it with other vehicles’ information in the area to determine the speed of traffic.

Two other systems, including an in-ground counter system supplied by Caltrans and a remote radar system, are merged with the transponder data to create accurate traffic speed information.

“We know that the same toll tag has passed Point A and Point B, and we can calculate the time that it took to travel between the two points, so we get very accurate information,” Metropolitan Transportation Commission Spokesman John Goodwin told Land Line.

Goodwin said because the transponder-tracking system uses encryption to keep drivers’ speed information, it cannot be used to track individual motorists or to ticket speeders.

“We have no way of identifying individual drivers, or individual vehicles belonging to the toll tags, so it’s absolutely anonymous,” Goodwin said. “In fact, with the FasTrak toll tags, the only time we know where you or your vehicle is, is at the toll plaza itself.”