Haul bulk liquids and gases safely — surge, high center of gravity, outage, and inspection.
Knowledge test only. There is no federal entry-level driver training requirement for the N endorsement, so no training certification is needed — you study, then you take your state's written test.
N.1
When you need the N endorsement
You need the N endorsement to haul liquids or gases in a permanently mounted cargo tank of large rated capacity, or a portable tank above the regulatory threshold. It is the tank and the bulk liquid that trigger it, not the product itself.
How you do it
1Confirm the vehicle has a bulk tank.
2Check the tank's rated capacity against the threshold.
3Carry the N endorsement whenever you move that vehicle loaded.
Check yourself
Can you explain what makes a vehicle a "tank vehicle" for endorsement purposes?
The short version
The N endorsement covers bulk liquid and gas tanks — know it applies before you drive one.
N.2
Liquid surge
Liquid in a partly filled tank moves. When you stop, the wave of liquid surges forward and can shove the truck into an intersection; it also rocks the vehicle after stops and during turns.
How you do it
1Expect surge whenever the tank is not full or empty.
2Brake gently and early.
3Stay alert after you stop — the surge can push you forward.
Check yourself
What happens to the liquid when a partly loaded tanker stops quickly?
The short version
Partly filled tanks surge — brake early, leave room, and expect a push after stopping.
N.3
Baffled vs. smooth-bore tanks
Baffles are bulkheads with holes that reduce front-to-back surge but do nothing for side-to-side surge. Smooth-bore tanks, often used for food products for sanitation reasons, have no baffles and the strongest surge of all.
How you do it
1Know which type you are driving.
2Treat smooth-bore tanks with extra caution.
3Never rely on baffles to control side-to-side motion.
Check yourself
Why is a smooth-bore tanker especially hard to control?
Liquids expand as they warm, so you must leave empty space — outage — so the tank does not overfill. Different liquids expand by different amounts. Dense liquids can also hit legal weight limits before the tank is physically full.
How you do it
1Leave the required outage for the product.
2Account for how much the liquid expands.
3Check weight — a heavy liquid may max out weight before volume.
Check yourself
Why can't you always fill a tank to the top?
The short version
Leave outage for expansion, and watch weight limits with dense liquids.
N.5
High center of gravity and rollover
Tankers carry weight high, giving a high center of gravity and a real rollover risk. Most tanker rollovers happen on curves and ramps at speeds that feel safe but are not.
How you do it
1Slow well below posted limits on curves and ramps.
2Make gentle steering inputs.
3Never over-correct or brake hard mid-curve.
Check yourself
Where do most tanker rollovers happen, and why?
The short version
A high center of gravity rolls tankers on curves and ramps — slow down and steer smoothly.
N.6
Inspecting a tank vehicle
Tank inspections add items normal trailers do not have: the tank shell for leaks and dents, manhole covers and vapor vents, valves and hoses, and any special-purpose equipment. Leaks are both a hazard and a legal violation.
How you do it
1Check the tank body, seams, and connections for leaks.
2Verify covers, vents, and valves are secure and working.
3Inspect hoses and special equipment before loading.
Check yourself
Name two tank-specific items you must inspect.
The short version
Inspect the shell, covers, vents, valves and hoses — a tank leak fails the trip.
Thresholds, distances and specific rules vary by state and change over time. Confirm everything here against your current state CDL manual before you test.