What 393.87B means in plain language
When cargo extends beyond the rear of your vehicle or hangs over the sides, federal safety rules require you to mark it with warning flags. These flags alert other drivers that your load is wider or longer than the truck itself, giving them crucial distance to navigate safely around you.
The regulation covers any load projection—whether it's a few inches of lumber, a pipe bundle, or equipment. The flags themselves must be visible and properly positioned so that oncoming and following traffic can see them in daylight and low-visibility conditions. Inspectors check that flags are present, securely attached, and positioned where they'll actually be seen. Missing flags, flags that have fallen off, or flags attached in places that don't warn approaching drivers all count as violations.
What our enforcement data actually shows
Across 13 million inspections in our database, 393.87B has generated 117 all-time citations, with 71 citations in the last 12 months and 16 in the last 90 days. This ranks the code at #1374 out of 3,036 FMCSR codes by citation volume—it's not one of the most common violations, but it's still actively enforced.
The out-of-service rate for 393.87B is 2.6%, meaning only 3 of the 117 citations resulted in your vehicle being placed out of service. That rate is substantially lower than the all-FMCSR average of 31.4%, indicating that inspectors typically cite this as a correctable defect rather than an immediate safety threat that grounds the truck.
The enforcement trend over the past 12 months shows variability month to month. May 2025 saw 9 citations, August had 7, and January 2026 had 9 with 1 out-of-service placement. This pattern suggests enforcement is consistent but not concentrated in any single season.
Who gets cited most
Our inspection records show Texas leads all states with 28 citations in the last 180 days, accounting for roughly half of all recent citations. Within Texas, the out-of-service rate stands at 10.7%—notably higher than the national 2.6% rate for this code—meaning inspectors in Texas have been more likely to ground vehicles for this violation. Illinois and North Carolina each recorded 2 citations in the same period, both with 0% out-of-service rates.
At the carrier level, our data shows fleets such as Stretch Transport LLC (USDOT 4258827) with 3 all-time citations for this code. Joe F Perry (USDOT 1789143), T Vines Trucking (USDOT 1799202), and several others each have 2 citations on record. These numbers reflect exposure to enforcement—not negligence—and suggest that carriers handling longer or wider loads should prioritize flagging procedures in their pre-trip routines.
How severe is this compared to similar codes
Vehicle maintenance codes span a wide range of enforcement intensity. Consider these peer violations:
393.9(a) — Inoperable required lamps has seen 660,737 citations with a 15.4% out-of-service rate. That's roughly 5,700 times more common than 393.87B and carries a significantly higher risk of being grounded.
396.3(a)(1) — Inspection/repair/maintenance general generated 236,919 citations and a 45.3% out-of-service rate—the highest among vehicle maintenance codes. Missing or improper flagging is far less likely to result in an out-of-service placement.
393.11 — Lighting devices/reflectors (179,734 citations, 1.8% OOS rate) is also a visibility-related code but nearly 1,500 times more frequent than 393.87B. The lower OOS rate on that code suggests that minor lighting defects are treated as correctable, similar to flagging violations.
In context, 393.87B is a low-volume, low-severity citation with minimal out-of-service risk.
How to avoid it
Missing or improperly positioned warning flags are entirely preventable with a disciplined pre-trip routine:
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Measure your load before departure. If cargo extends more than a few inches beyond the rear bumper or beyond the widest part of your trailer, flagging is required. Don't rely on guesswork; use a tape measure at the loading dock.
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Inspect flags visibly and physically. During your walk-around, verify that flags are present, securely fastened, and not torn or faded. Our inspection data shows common co-occurring violations include brake and coupling defects, suggesting that inspectors checking flagging are also examining other trailer systems—so a thorough walk-around catches multiple hazards at once.
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Position flags where traffic will see them. Flags should be at the outermost point of the projection, high enough to be visible from the driver's seat of an oncoming vehicle. Don't tuck them where they'll be hidden by the cargo or the truck body.
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Carry spare flags and fasteners. If a flag comes loose during transit, you'll need to replace it before the next inspection. Many carriers whose vehicles show up frequently in our data—particularly those running loads on Peterbilts, Kenworths, and Frieghtliners—operate in high-inspection areas like Texas. Having backup flags on hand avoids a citation during a routine roadside check.
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Confirm flagging after shifting cargo. If you stop and adjust or redistribute your load, verify that flags are still in place and properly positioned. Vibration and wind can loosen even well-installed flags.
This violation is rare enough that a single citation is unlikely to trigger serious CSA consequences, but it's common enough in Texas and among carriers handling projecting loads that building it into your pre-trip discipline is worth the 30 seconds it takes.