What 172.331 means in plain language
FMCSR 172.331 covers the proper marking of bulk packages during transport. When you're carrying hazardous materials in bulk form—whether in tank trucks, cargo tanks, or portable tanks—those containers must display the correct identification and warning markings so that emergency responders, other drivers, and inspection officers can immediately recognize what's inside.
The regulation requires that bulk packages meet specific marking standards depending on the material class and hazard type. This isn't about faded placards or worn labels—it's about ensuring the bulk container itself is marked according to DOT hazmat rules. Missing markings, incorrect markings, or markings applied to the wrong part of the tank all violate this code.
If you haul propane, acids, bulk chemicals, or other regulated materials, your tank must carry the proper DOT markings before it leaves the yard and every time it's on the road.
What our enforcement data actually shows
Across our 13 million roadside inspection records, 172.331 has been cited 33 times all-time, with 12 citations in the last 12 months and 1 in the last 90 days. This makes it rank #1763 out of 3,036 FMCSR codes by citation volume—a relatively uncommon violation.
However, when officers do cite this code, the consequences are serious. Our data shows a 54.5% out-of-service rate for this violation. That's significantly higher than the all-FMCSR average of 31.4%, meaning more than half of drivers cited for 172.331 had their vehicle pulled from service on the spot. This reflects the safety-critical nature of hazmat markings: inspectors treat improper bulk package markings as a direct safety risk and act accordingly.
The relatively low citation count combined with the high OOS rate suggests this violation is caught less frequently than some others, but when it is caught, enforcement is swift and strict.
Who gets cited most
Our inspection records show enforcement of 172.331 is concentrated in a small number of states. In the last 180 days, Texas led with 4 citations, 2 of which resulted in out-of-service orders (50.0% OOS rate).
Looking at carriers across all-time data, USA LOGISTICS INC (USDOT 1892938) appears twice in our citation records for this code. Other carriers cited include ESTES EXPRESS LINES, NOVA MUD INC, SUBURBAN PROPANE LP, and FRED GARRISON OIL CO, each with single citations. Our data shows fleets operating in bulk hazmat transport see these violations occur, though the overall frequency remains low. This pattern reflects the specialized nature of bulk package transport—violations are more concentrated among carriers actively hauling hazmat in bulk form.
How severe is this compared to similar codes
To understand where 172.331 sits in the hazmat enforcement landscape, look at related codes in the Hazardous Materials category:
177.834A (General loading/unloading of hazmat) has been cited 3,954 times with a 99.2% out-of-service rate—vastly more frequent and almost always resulting in vehicle removal.
172.502(a)(1) (Placarding general requirements) has 1,820 citations with an 18.5% OOS rate—more common than 172.331 but much less likely to trigger an out-of-service order.
172.516(c)(6) (Placard damaged, deteriorated, or obscured) shows 1,796 citations but only a 1.6% OOS rate, indicating inspectors view physical damage to placards as less severe than missing or incorrect markings on bulk containers.
The data indicates that 172.331 occupies a middle tier: rarer than general placarding violations, but treated more seriously when cited. Your 54.5% OOS rate exceeds most marking-related codes and approaches the severity of active hazmat loading and unloading violations.
How to avoid it
Since 172.331 enforcement is rare but harsh, the best strategy is prevention through pre-trip inspection and carrier compliance processes:
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Inspect your bulk container before every departure. Walk around the tank and verify that all required DOT markings are present, legible, and properly positioned. Check that the product ID number, hazard class labels, and any required placards match your bill of lading. Don't assume markings from the last load are still correct.
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Know your material classification. Bulk hazmat marking requirements vary by product class. Before loading, confirm with your dispatcher or safety manager what markings your specific commodity requires. Propane, acids, and flammable liquids have different marking rules.
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Verify markings during pre-inspection. Our records show that when 172.331 violations appear alongside 172.504A (Placarding for Table 1 materials) and 180.340 violations in the same inspection, the issue often stems from incomplete or inconsistent hazmat documentation. Cross-check your shipping papers against your tank markings before rolling.
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Report worn or missing markings to your carrier immediately. If you notice markings fading, peeling, or becoming obscured during your trip, contact dispatch and request repair or replacement before your next inspection. Don't assume you can continue—a 54.5% OOS rate means inspectors are acting on this.
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Document your pre-trip inspection. Keep a photo or written record of your tank's markings before departure. This protects you if weather, road debris, or wear causes damage mid-route and gives you proof the markings were correct when you left.
Bulk hazmat is a specialized business with specialized rules. The low citation count means most drivers get it right, but the high OOS rate confirms that regulators prioritize enforcement when markings are wrong. Treat your pre-trip marking check as seriously as you treat your brake inspection.