If you haul gasoline or diesel, the placards are required and the numbers are specific. Gasoline is UN 1203, a Class 3 flammable liquid. Diesel ships as UN 1993 or UN 1202, also Class 3. Aviation turbine fuel is UN 1863. Any cargo tank carrying these needs a red FLAMMABLE placard on all four sides with that four-digit identification number showing, and for a tank truck that holds true no matter how little product is aboard.
The four-digit numbers that belong on your rig
Every hazardous material moving on the road has a UN identification number and a hazard class assigned in the 49 CFR 172.101 table. For the products a jobber runs out of a bulk plant, the numbers are short and worth memorizing.
- Gasoline, UN 1203. Class 3 flammable liquid. Aviation gasoline (avgas) carries the same UN 1203.
- Diesel fuel, UN 1993 or UN 1202. Class 3. UN 1202 is the entry for diesel fuel, gas oil, and light heating oil; UN 1993 covers flammable liquids not otherwise specified and is also used for diesel on many shipping papers.
- Aviation turbine fuel (Jet A, Jet A-1), UN 1863. Class 3 flammable liquid.
- Fuel oil, UN 1202 or UN 1993. Heavier heating oil delivered to homes and burners.
All of these sit in Class 3, so the placard is the red diamond with the flame symbol and a 3 at the bottom. The four-digit number identifies the exact product for first responders.
When placarding is required, and why your tank truck almost never gets a pass
The rule people quote is the 1,001-pound threshold in 49 CFR 172.504. It works like this. The hazard classes split into two tables. Table 1 materials (explosives, poison gas, and a few others) require placards at any quantity. Class 3 flammable liquids like gasoline and diesel sit in Table 2, and Table 2 materials only trigger placarding once the aggregate gross weight on the vehicle reaches 1,001 pounds or more.
That threshold matters for a pickup carrying a few drums or totes. It rarely helps a fuel hauler, because of the exception written into 172.504(c): the under-1,001-pound relief does not apply to bulk packagings. A cargo tank is a bulk packaging. So a bobtail or a transport carrying gasoline or diesel must be placarded even when it is running nearly empty. If there is regulated product in the tank, the placards go up. This is the point most people get wrong when they read the 1,001-pound number and assume a light load lets them skip it.
For the difference between the two trucks doing this hauling, see transport vs bobtail fuel delivery.
Where the UN number actually goes
Displaying the placard is only half of it. On a cargo tank you also have to show the identification number, and 49 CFR 172.332 and 172.336 give you two ways to do it. You can put the four digits across the center of the placard itself, or you can display them in black on an orange panel placed right next to the placard. Either way the number shows on both sides and both ends of the tank.
There is a wording option worth knowing. Under 49 CFR 172.542, a gasoline cargo tank may carry the word GASOLINE on the flammable placard in place of FLAMMABLE. A fuel oil tank may show FUEL OIL. This is optional. A plain red FLAMMABLE placard with the correct UN number is always compliant.
Mixed loads: gasoline and diesel in the same bobtail
Most delivery rigs are compartmented and carry more than one product on a run. Gasoline and diesel are both Class 3, so the truck wears FLAMMABLE placards, and each product still needs its identification number shown. In practice the rig displays 1203 for the gasoline compartment and 1993 or 1202 for the diesel, on the sides near the compartment that holds each product. The ends of the tank follow the ID number rules in 172.336 for multi-product loads. If you are ever unsure how to mark a specific split load, the fastest answer is your cargo tank builder or your compliance vendor, because the placement depends on your tank's compartment layout.
Propane and other products play by different rules
Not every fuel a jobber moves is a Class 3 liquid. Propane is UN 1075, a Class 2.1 flammable gas, and it wears a FLAMMABLE GAS placard, not the liquid placard. If propane is part of your book, the marking and handling rules diverge from your gasoline and diesel fleet. That side of the business is covered in propane and LP-gas distribution. The takeaway is simple: match the placard and the UN number to the actual product class, and never carry a gasoline placard on a load it does not describe.
The placard is one line on a longer compliance list
Placarding rarely fails on its own at a roadside inspection. It fails alongside the paperwork. A placarded load needs shipping papers that name the product, its UN number, class, and packing group (49 CFR 172.200), plus emergency response information and an emergency contact. PHMSA and DOT enforce this, and civil penalties for hazmat violations run into the tens of thousands of dollars per violation. A missing placard, a wrong UN number, and an incomplete manifest are three separate findings on the same stop.
The pattern I see in the back office is that the placarding itself is fine and the records behind it are scattered across a driver's clipboard, a dispatcher's spreadsheet, and a filing cabinet. When an inspector or an auditor asks for the shipping paper on a specific delivery from four months ago, the scramble is where the cost shows up. Compliance gaps are one of the quiet drains covered in where fuel margin leaks, and clean delivery records are the cheapest insurance against them. This is one place where the right back-office system earns its keep by tying each delivery to its product, UN number, and paperwork automatically.
FastDragon builds that back office for fuel jobbers and marketers, so every delivery ticket, product code, and compliance record lives in one place instead of three. If pulling a clean shipping-paper trail for any past load is harder than it should be, that is worth a conversation.
Questions people ask
Does a driver need a hazmat endorsement to drive a placarded fuel truck?
Yes. Once a load requires placards, the driver must hold a Hazardous Materials Endorsement (HME) on their CDL, which involves a TSA background check and a written knowledge test. This is separate from the placarding rule itself, but the two go together: if the rig is placarded, the driver behind it needs the endorsement.
Does an empty tank truck still have to be placarded?
Usually, yes. A cargo tank that last carried gasoline or diesel and has not been cleaned and purged of vapor and residue is still treated as containing hazardous material, so the placards stay up. The tank has to be emptied and cleaned to the standard in the regulations before the placards can come off.
Do local farm or short-haul deliveries qualify for any exemption?
The materials of trade exception in 49 CFR 173.6 relieves small quantities carried in support of a business, but it is written around limited amounts and does not cover a bulk cargo tank hauling fuel for delivery. A tank truck delivering gasoline or diesel does not fit that exception and is placarded like any other hazmat load.
Who writes and enforces these placarding rules?
The rules live in the federal Hazardous Materials Regulations at 49 CFR, administered by PHMSA. Enforcement on the road is handled by DOT and FMCSA inspectors and by state officers at weigh stations and roadside stops. Both the placard and the shipping paperwork are checked at the same inspection.