Transponder support & questions

Find technical support and answers to your questions about transponders, including troubleshooting tips and other helpful information.

Transponders identify commercial vehicles so the legal weight, safety rating and registration information can be verified as the commercial vehicle approaches the weigh station. This process allows safe and legal carriers to continue driving so officers can focus on high-risk carriers.

Adding a transponder

Purchase a transponder

Register a transponder (WA, ID, SD, NY & CT)

Registering transponders in other systems

Provide the transponder number and commercial vehicle information.

Registering PrePass transponders in Washington

Requests to register a PrePass transponder must come directly from PrePass.

Multiple transponders

  • Having multiple transponders in a commercial vehicle is not recommended.
  • A single transponder should be registered for all electronic screening systems.


Bypass minimum requirements

  • Current commercial vehicle registration
  • USDOT Number of the Carrier Responsible for Safety
  • Carrier safety score of 74 or below (WSP discretion)
  • All required taxes and fees must be paid
  • Commercial vehicle and load must have a legal height and weight

Common red light reasons

  • Overweight, over axle weight, or overheight
  • Carrier safety score of 75 or above
  • Expired commercial vehicle registration.
  • The transponder is not registered correctly (still assigned to an old VIN)
  • Random pull-in rate set by officers at the weigh station
  • Special emphasis, federal government inspections, or other mandated inspections

Preventing red lights

  • Center the commercial vehicle in the Weigh-In-Motion (WIM) lane
  • Maintain a steady highway speed of around 55 miles per hour
  • Provide at least a three second gap between vehicles
  • Secure tarps so the wind does not trip the over-height detector
  • Avoid dark, metallic window tinting that can interrupt the transponder signal
  • Avoid metallic windshield visors that can interrupt the transponder signal
  • Use only one transponder in your commercial vehicle
  • CB radios may cause an interruption of the signal to the transponder

No light

A battery issue or the transponder location typically causes no lights in Washington. Transponders can be placed in the following locations:

  • Near the center of the windshield
  • On the passenger side of a divided windshield
  • Either three to six inches from the top or just above the dashboard
  • Try to keep it a couple inches away from any metal

Transponder information

Follow In-Cab signal

  • If the transponder light does not match the roadside sign, follow the In-Cab signal

Transponder Number

The transponder number is located on the device near the barcode:

  • 20xxxxxx or (xxx)54xxxxxxx
  • 24xxxxxx or (xxx)60xxxxxxx (typically gray)
  • 28xxxxxx or 67xxxxxxx (typically black)
  • 2Exxxxxx or 77xxxxxxx (typically white)


  • Transponders have a three to five year average battery life (depending on use)
  • Transponders do not have replaceable batteries
  • Once the transponder stops working, you will need to purchase a new transponder
  • Do not return non-working transponders purchased from us to WSDOT
  • Follow your regional guidelines for lithium ion batteries when disposing a transponder
  • To unregister before disposing of, email or fax the transponder number with a request to delete/cancel to the contact information below

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.