What 172.336(c) means in plain language
When you transport hazardous materials, your vehicle must display proper identification numbers in the locations and formats specified by federal rules. Code 172.336(c) requires that you follow a specific table of provisions for where and how those ID numbers appear on your truck and placards.
This isn't about having the right hazmat label or placard—it's about the exact placement and visibility of the identification numbers that inspectors use to verify what's actually in your tank or cargo. If an inspector stops you and finds those numbers missing, illegible, or positioned incorrectly according to the table, you'll be cited for this violation.
What our enforcement data actually shows
Across our database of 13 million+ roadside inspection records, we have documented 32 all-time citations for 172.336(c). In the last 12 months, there were 0 citations, and in the last 90 days, 0 citations as well. This makes 172.336(c) one of the least-cited FMCSR codes—ranked #1775 out of 3,036 codes by citation volume.
When citations are issued, the severity is moderate. Our data shows a 46.9% out-of-service rate for this violation. That's higher than the all-FMCSR average of 31.4%, meaning roughly 15 out of every 32 citations resulted in the vehicle being placed out of service. However, the extremely low citation count means this violation is rarely encountered in routine inspections.
Who gets cited most
Our enforcement records do not include geographic (state-level) breakdowns detailed enough to name specific top states. However, at the carrier level, the data shows that TFORCE FREIGHT INC (USDOT 121058) appears most frequently in our citation records for this code, with 4 citations. DANIEL CANO GARCIA (USDOT 3709951) had 2 citations, and several other carriers—including MID THUMB TRUCKING CO, B & B OIL CO INC, and KENDRICK OIL CO—each had 1 citation on record. This pattern reflects the rarity of the violation rather than systematic non-compliance by any single fleet.
Vehicle makes cited for this violation include a mix of tanker and freight equipment: PTRB and VOLV models each had 4 citations, while KW units had 3. This suggests the violation can occur across various hazmat transport configurations.
How severe is this compared to similar codes
Other hazardous materials codes in the same regulatory family show much higher citation and out-of-service rates. For example, 177.834A (general loading/unloading hazmat violations) has 3,954 citations with a 99.2% out-of-service rate, and 177.834(a) has 3,839 citations with a 97.9% OOS rate. Those violations directly endanger cargo and personnel, so the enforcement response is severe.
Code 177.817(a) (placarding violations) sits in the middle, with 2,274 citations and a 75.1% out-of-service rate. By contrast, 172.516(c)(6), which addresses damaged or obscured placards, has 1,796 citations but only a 1.6% out-of-service rate—suggesting inspectors view display defects on a spectrum of severity. Your 172.336(c) citation falls between these examples: uncommon, but when cited, enforced with a moderate OOS rate that reflects concern about visibility and compliance.
How to avoid it
Before you load:
- Review the placard and identification number table in 49 CFR 172.336 before each hazmat run. Know exactly where ID numbers must appear on your vehicle.
- Walk your truck from all four sides during pre-trip. Check that all required ID numbers are present, legible, and positioned per the table.
- On tankers and cargo tanks especially, ensure numbers are not faded, covered by dirt or ice, or obscured by cargo straps or equipment.
- If your vehicle uses removable placards or ID numbers, confirm they are secured and will not shift or fall off during transit.
During operations:
- Do not cover identification numbers with tarps, chains, or other equipment, even partially.
- After fueling or transfers at hazmat facilities, do a quick visual walk-around to confirm nothing shifted or became obscured.
- If road dirt or weather reduces visibility, stop in a safe location and clean the numbers before proceeding to your next stop.
Equipment selection and maintenance:
- If you operate a PTRB, VOLV, or KW unit regularly, add a pre-trip checklist item specifically for ID number inspection on those makes.
- Use permanent, high-contrast ID number affixes rather than paint-on numbers when possible—they last longer and remain legible through seasons.
- Keep spare adhesive-backed ID numbers in your cab so you can replace a damaged one if you spot it between scheduled maintenance.