Commercial Vehicle - Transponder Program

Photo of the transponder

The transponder program allows trucks to bypass weigh stations by electronically verifying a truck's legal weight, safety rating, and credentials as the truck continues down the road at freeway speeds.

An integral part of making the program work is the use of a transponder. A transponder is a small electronic device that attaches to the inside of the vehicle’s windshield. Here is how the transponder works:

  • Each transponder has a unique serial number that is assigned to a specific vehicle in the database.
  • As the vehicle approaches a weigh station there are two roadside antennas.
  • The first antenna reads the transponder serial number, identifies the vehicle and checks the status of the motor carriers safety rating and the vehicle’s credentials.
  • The vehicle weight is calculated as the vehicle crosses the weigh in motion device and is verified against the vehicles registered gross vehicle weight.
  • Based on the safety rating, credential and weight check the second antenna sends a signal back to the transponder.
  • A green light indicates the checks were all satisfactory and the vehicle may bypass the weigh station.
  • A red light indicates the driver needs to report to the weigh station for closer inspection.

After receiving a red or green light on the transponder, the light will continue to flash intermittently for approximately 15 minutes. There is nothing wrong with the transponder. This is built in protection for the carrier in case the driver is pulled over by law enforcement. The transponder signal allows the officer to verify the signal that was transmitted.


Transponder Administration