Transponder program & benefits

Learn about the transponder program, which allows commercial vehicles to bypass weigh stations by electronically verifying the legal weight, safety rating, and credentials as the commercial vehicle continues down the road at freeway speeds.


A transponder used for commercial vehicle bypass weigh stations

A transponder used for
commercial vehicle bypass
weigh stations.

About transponders

Transponders are an essential part of making the electronic screening program work. A transponder is a small electronic device attached to the inside of the windshield with a unique serial number. The transponder serial number is specific to a commercial vehicle in our database.

  • Roadside equipment is located approximately ½ mile before the weigh station.
  • An antenna reads the transponder serial number to identify the commercial vehicle and look up the registration/cab card.
  • Weigh-in-motion scales in the road calculate the weight and axle distances of the commercial vehicle.
  • Electronic screening software checks the motor carrier’s safety rating, commercial vehicle registration information, weight, and height for violations.
  • The second antenna sends a signal back to the transponder.
  • Green lights indicate no violations. The commercial vehicle may bypass the weigh station.
  • Red lights indicate a possible violation. The commercial vehicle needs to report to the weigh station for a closer inspection.
  • If the transponder light does not match the roadside signs, follow the in-cab signal.
  • If the transponder has no light, follow the roadside signs.

A red or green light will continue to flash intermittently for approximately 15 minutes. There is nothing wrong with the transponder. The flashing light 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.



  • Law enforcement can focus resources on high-risk and non-inspected carriers.
  • Fewer commercial vehicles pulling in and out of weigh stations reduces the risk of collisions.


  • Improves productivity and efficiency of motor carriers and drivers.
  • Carriers can save time and money by not idling at the weigh station.
  • Reduces diesel usage and carbon dioxide emissions.
  • Reduces costly paperwork for government and motor carriers through automated reporting and record-keeping.


  • Improves enforcement efficiency by targeting high-risk carriers.
  • Improves the accuracy, integrity, and verification of credentials through sharing of commercial vehicle data between states and the Federal Motor Carrier Safety Administration (FMCSA).
  • Standardizes data exchanges and streamlines work for participating motor carriers, drivers, and regulators.
  • Allows motor carriers to quickly obtain information from governing and enforcement agencies.

Slow down – lives are on the line. 

In 2023, speeding continued to be a top reason for work zone crashes.

Even one life lost is too many.

Fatal work zone crashes doubled in 2023 - Washington had 10 fatal work zone crashes on state roads.

It's in EVERYONE’S best interest.

95% of people hurt in work zones are drivers, their passengers or passing pedestrians, not just our road crews.