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Short answer: yes, and possession is enough. Under 49 CFR 392.71 you may not use a radar detector in a commercial motor vehicle, and you may not operate a CMV that is equipped with or contains one. Unplugged in a side pocket still counts. This is federal, so it applies in all 50 states regardless of local law.
Which vehicles this covers
| Weight | 10,001 lbs or more, used in interstate commerce |
|---|---|
| Passengers, paid | More than 8 including the driver, for compensation |
| Passengers, unpaid | More than 15 including the driver |
| Hazmat | Any vehicle carrying placarded hazardous materials |
If your vehicle meets any one of those, the rule applies to you.
The fine is not the problem. The CSA points are.
Most write ups stop at the dollar figure. For anyone driving for a living, that is the least important part.
| Consequence | Detail |
|---|---|
| CSA points | 5 points in the Unsafe Driving category |
| Civil penalty | Up to $4,812 for a driver |
| Carrier liability | The rule also prohibits carriers from requiring or permitting a driver to violate it |
A fine is paid once and forgotten. CSA points attach to the carrier’s Unsafe Driving score, and that score is what shapes inspection frequency, insurance pricing and whether shippers want to work with the carrier at all. Five points from something as avoidable as a detector in the glovebox is a bad trade for any driver, and an expensive one for a small fleet.
If you are an owner operator, both halves land on you.
The mistake that catches people out
Drivers who run a detector in their personal car often leave it in the cab without thinking, or keep it stowed for use on days off. The regulation does not care. It covers a vehicle that contains a detector, so a boxed unit behind the seat is the same violation as one mounted and running.
The other common assumption is that state law decides this. It does not. State law governs your private car. The federal rule sits on top for commercial vehicles, which is why a detector that is entirely legal in your own vehicle is still prohibited in your truck in the same state.
What is allowed instead
- Crowdsourced alert apps. Waze and similar report police sightings and detect nothing, so they fall outside the rule.
- Speed limit aware navigation. Most modern units warn you against the posted limit.
- A dash cam. Legal in a CMV and considerably more useful after an incident. See our dash cams for semi trucks guide.
Related reading: radar detector laws by state and laser jammer laws by state.
Frequently asked questions
Are radar detectors illegal in commercial vehicles?
Yes. 49 CFR 392.71 prohibits using a radar detector in a commercial motor vehicle, and prohibits operating a CMV that is equipped with or contains one. It applies nationwide, in every state, territory and on tribal land, regardless of state radar detector law.
Does the detector have to be switched on?
No. Possession is the violation. A detector that is unplugged, boxed, or sitting in a side pocket still counts. The regulation covers a vehicle that is equipped with or contains a radar detector.
Which vehicles count as commercial motor vehicles?
Broadly, vehicles of 10,001 lbs or more used in interstate commerce, vehicles carrying more than 8 passengers for compensation, vehicles carrying more than 15 passengers without compensation, and any vehicle carrying placarded hazardous materials.
What is the penalty?
A violation carries 5 CSA points in the Unsafe Driving category. Civil penalties for a driver can reach $4,812. The carrier is also liable, since the rule prohibits carriers from requiring or permitting a driver to violate it.
Do state laws override the federal rule?
No. State law decides whether a radar detector is legal in a private passenger car. The federal rule applies on top of that for commercial vehicles, so a detector that is perfectly legal in your own car is still prohibited in your truck.