What 390.21(g) means in plain language
FMCSR 390.21(g) addresses vehicle marking and identification requirements for commercial motor vehicles. The regulation requires that certain information be displayed on or affixed to your vehicle in a manner that meets federal standards. This falls under the broader vehicle marking rules that ensure trucks and their operations can be properly identified and tracked by enforcement officers and the public.
The specific requirement covers how and where identification must be applied to your vehicle. Violations occur when the required marking is missing, illegible, improperly positioned, or fails to meet the dimensional and material standards set out in the regulation. Even if the information itself is correct, placement or visibility issues can result in a citation.
What our enforcement data actually shows
Across our 13 million+ real roadside inspection records, 390.21(g) has been cited only 32 times all-time, making it ranked #1775 of 3,036 FMCSR codes by citation volume. In the last 12 months, we recorded just 1 citation, and none in the last 90 days. This code is extremely rare in roadside enforcement.
None of the 32 all-time citations resulted in an out-of-service order—the OOS rate is 0.0%. This stands in stark contrast to the all-FMCSR average OOS rate of 31.4%, indicating that 390.21(g) violations are typically treated as administrative or correctable defects rather than safety-critical failures. When inspectors encounter this violation, they document it but do not immediately remove the vehicle from service.
Who gets cited most
Our inspection records show that NORTON TRANSPORT INC (USDOT 925129) has the most citations for this code with 3, followed by TOMI EXPRESS LLC (USDOT 4045827) and RYDER TRUCK RENTAL INC (USDOT 16130), each with 2 citations. The remaining carriers in our top-10 list each have 1 citation. The distribution is highly dispersed—this is not a code that clusters within a few carriers or fleets.
How severe is this compared to similar codes
390.21(g) sits within the General/Admin category alongside several high-volume peer codes. The most frequently cited similar codes are 390.21TB2-DOT with 74,663 citations and 0.0% OOS rate, and 390.21T(b) with 61,097 citations and 0.0% OOS rate. Even 390.21(a) (Vehicle marking requirements) generates 25,872 citations—nearly 800 times more than 390.21(g)—yet maintains a 0.0% OOS rate as well.
This pattern tells you that marking and identification violations as a family are treated leniently in enforcement. They are correctable defects. Your citation is not indicative of a serious safety problem; it is an administrative finding that you are expected to remedy and document.
How to avoid it
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Pre-trip: inspect all required markings — Walk around your vehicle before departure and verify that all DOT numbers, carrier identifiers, and hazmat placards (if applicable) are present, fully legible, and securely fastened. Use a flashlight to check at night or in dim light; fading or obscured text is a common citation trigger.
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Check mounting hardware and fasteners — Ensure that any placard holders, decals, or painted markings are not peeling, cracked, or hanging loose. Movement or vibration during transit can loosen or degrade markings; secure them firmly with weatherproof hardware.
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Verify compliance with dimensional requirements — Markings must meet specific height, contrast, and font standards. If you have recently had signage replaced or repositioned, confirm with your carrier's safety department that the new installation meets 390.21(g) specs before hitting the road.
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Document corrections immediately — If an inspector cites you or you discover a marking defect during pre-trip, photograph the vehicle before and after repair. Keep records with your logbook or driver file; this creates a clear record for your carrier and helps you respond to any follow-up inquiries.