What 392.71(a) means in plain language
FMCSR 392.71(a) prohibits drivers from using or equipping a commercial motor vehicle with a radar detector. This means you cannot operate a CMV that has a radar detector installed or in use, whether you're actively using it or it's simply mounted in your cab.
The regulation applies to all radar detection devices—including standalone units, smartphone apps, or integrated systems that alert you to speed enforcement equipment. The rule is straightforward: if you're driving a CMV, a radar detector cannot be part of that vehicle's equipment or operation.
This is a safety and compliance standard. The Federal Motor Carrier Safety Administration treats radar detector use as incompatible with the professional operation of commercial vehicles, regardless of the legality of such devices in passenger vehicles in your state.
What our enforcement data actually shows
Our inspection records show that 392.71(a) citations are relatively uncommon in the enforcement landscape. Across 13 million roadside inspections in our database, we have recorded 2,232 all-time citations for this violation, ranking it #515 out of 3,036 FMCSR codes by citation volume.
Notably, there have been zero citations for this code in the last 12 months and zero in the last 90 days. This recent absence suggests either improved compliance among drivers or a shift in enforcement priorities.
When 392.71(a) citations do occur, they are never placed out of service—the OOS rate is 0.0%. This contrasts sharply with the all-FMCSR average OOS rate of 31.4%. In other words, inspectors cite this violation but do not remove the vehicle from service, meaning you can typically continue operating after receiving the citation.
Who gets cited most
The data in our database indicates that certain carriers and vehicle types have seen more 392.71(a) citations than others. Our records show fleets such as United Parcel Service Inc with 14 citations and High Speed Demand Inc with 5 citations in this category.
Freight trucks dominate the citation records by vehicle make. The FRHT platform leads with 198 citations, followed by PTRB with 158 citations and Freightlin with 150 citations. Kenworth and Peterbilt models also appear frequently, with 64 and 74 citations respectively.
This distribution likely reflects the volume of freight and parcel delivery operations in the trucking industry, which naturally represent larger segments of the commercial vehicle population on inspected roadways.
How severe is this compared to similar codes
392.71(a) sits in the Unsafe Driving category alongside several high-volume violations. To put citation frequency in context:
- 392.2 (Operating a CMV while ill or fatigued) has generated 1,208,164 citations with a 0.8% OOS rate—more than 540 times the citation volume of 392.71(a), yet a comparable OOS outcome.
- 392.2-SLLEQP (operating while fatigued) shows 72,352 citations and a 2.4% OOS rate, meaning enforcement in that area carries slightly higher physical removal likelihood.
- 392.2-SLLS2 (speeding 6–10 mph over limit) generated 72,337 citations with a 0.0% OOS rate—similar to 392.71(a) in that citations rarely result in out-of-service placement.
The key takeaway: 392.71(a) violations are enforced infrequently relative to other unsafe driving codes, and when they are cited, the consequence is administrative citation rather than immediate vehicle removal.
How to avoid it
Complying with 392.71(a) is straightforward but requires intentionality:
-
Remove or disable any radar detection equipment before operating a CMV. This includes dashboard-mounted units, windshield-mounted devices, and smartphone apps that serve radar detection functions. Do not assume a device is legal in a passenger car and therefore acceptable in a commercial vehicle—the federal rule is absolute.
-
Inspect your cab during pre-trip inspection. Check for any detection hardware, whether hardwired or portable. If you inherit a truck from another driver, verify that no radar detector is concealed in the glove box, under the seat, or behind the visor.
-
Understand that state legality does not override federal regulation. Even in states where radar detectors are legal for private vehicles, FMCSR 392.71(a) applies uniformly to all commercial motor vehicles. Compliance is a federal mandate, not a state-by-state choice.
-
Do not attempt to circumvent enforcement radar or laser speed measurement. The prohibition on radar detectors reflects a broader expectation that commercial drivers will maintain lawful speeds through attention to posted limits and road conditions, not through countermeasures.
Since citations for this violation have not been recorded in the last 90 days, enforcement may be sporadic. However, that does not mean the rule is no longer enforced or that compliance is optional. Treat it as a fixed compliance requirement and remove any radar detection equipment from your vehicle immediately.