What 178.337-17(a) means in plain language
An MC331 tank is a specific type of pressure vessel used to transport certain hazardous materials by road. The regulation requires that this tank carry a permanent metal identification plate affixed to it. This plate serves as proof that the tank was manufactured and tested to Department of Transportation standards, and it records critical information about the tank's specifications, test dates, and authorized contents.
When an inspector finds an MC331 tank without this metal plate—whether it's been removed, is missing, corroded beyond readability, or never installed—the vehicle is cited under 178.337-17(a). The plate isn't just paperwork; it's physical evidence that the tank is legal to use for hazmat transport. Without it, inspectors cannot verify that the vessel meets safety requirements.
What our enforcement data actually shows
This violation is extremely rare in roadside enforcement. Across our database of 13 million+ inspection records, we've recorded only 7 citations for a missing MC331 metal identification plate throughout all-time history. In the last 12 months, we've seen zero citations for this code, and in the last 90 days, zero citations as well.
None of the 7 all-time citations resulted in an out-of-service order. The OOS rate for 178.337-17(a) is 0.0%—meaning every cited driver was allowed to continue operating. This stands in sharp contrast to the all-FMCSR average OOS rate of 31.4%. The near-total absence of out-of-service action reflects that inspectors typically treat a missing plate as a correctable defect rather than an immediate safety emergency, though the violation must still be addressed.
By citation volume, 178.337-17(a) ranks #2312 out of 3,036 FMCSR codes. This low frequency means you're in a very small group of drivers who have received this citation.
Who gets cited most
Our inspection records show that no state dominates citations for this code. The 7 all-time citations are distributed across multiple carriers, each with a single citation: LAMPTON-LOVE INC, 48FORTY SOLUTIONS LLC, KTI EXPRESS LLC, DEL GAS CORP, WINDSTAR TRUCKING LLC, MANVIR TRUCKLINES INC, and VILLA BROTHERS LONG HAULING LLC. The rarity of this violation means there is no meaningful pattern of repeat offenders or regional concentration.
Vehicle makes cited include FORD, FRHT (Freightliner), INTL (International), and others, but again, each represents only a single citation in our database, so no specific truck type is disproportionately associated with this violation.
How severe is this compared to similar codes
This citation sits at the low-severity end of hazmat inspection violations. Compare it to other codes in the Hazardous Materials category:
- 177.834A-HMC (General loading/unloading hazmat) has logged 3,954 citations with a 99.2% OOS rate—a dramatically different enforcement posture.
- 177.817(a) (Placarding violation) shows 2,274 citations with a 75.1% OOS rate, reflecting serious concern about hazmat identification in transit.
- 172.602(c)(1) (Maintenance/accessibility of Emergency Response information) has 1,464 citations with a 0.0% OOS rate, matching the zero OOS rate you received.
The absence of out-of-service action for a missing metal plate suggests that federal inspectors view it as a documentary or maintenance issue—important to correct, but not an immediate operational hazard in the way that improper loading, placarding, or emergency response failures are treated.
How to avoid it
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Before you accept a tank vehicle for hazmat service: Walk around the MC331 tank and verify that the metal identification plate is securely mounted and legible. The plate should be permanently affixed, typically near the top or along the side of the tank, and it must display the manufacturer's name, the tank's date of manufacture, and test certification dates. If the plate is missing, cracked, or unreadable, do not depart; report it to your carrier's maintenance team or fleet manager immediately.
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Document the plate condition during your pre-trip: Take a photo or note the plate's location and readable text. This creates a record that the tank was compliant when you began your trip. If an inspector stops you and claims the plate is missing or obscured, you have contemporaneous evidence.
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Check for corrosion and rust: Even if a plate is present, salt spray, moisture, or prolonged exposure can corrode the metal or obscure the lettering. During seasonal transitions or after traveling through wet conditions, inspect the plate area for rust or deterioration that might render it unreadable in the inspector's eyes.
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Communicate with your maintenance department: If your fleet operates multiple MC331 tanks, ensure that your maintenance logs include regular verification that all plates are present and legible. A single missing or corroded plate can ground a vehicle during a roadside inspection, so preventive maintenance is far cheaper than downtime.
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Understand your tank's history: If you're assigned a tank vehicle that's new to you or has been in storage, ask your dispatcher whether the tank has been recently inspected or certified. Some tanks in long-term service may have aging plates that are harder to read; proactive recertification or plate replacement by the tank manufacturer keeps you compliant.