20 Tanker Endorsement (N) Practice Questions & Answers

Every Tanker Endorsement (N) practice question from the CDL Practice Test, with the correct answer and a short explanation.

Start practice test →

1. Federal rules require a tank vehicle (N) endorsement when a driver hauls a liquid or liquid gas in tanks meeting which rated-capacity thresholds?
- A.An aggregate rated capacity of more than 3,000 gallons, with no limit on the individual tank
- B.Any single tank with a rated capacity of more than 100 gallons, no matter the aggregate capacity
- C.An individual rated capacity of more than 119 gallons and an aggregate rated capacity of 1,000 gallons or more✓ Answer
- D.An individual rated capacity of 119 gallons or less and an aggregate rated capacity of 500 gallons or more
Both thresholds must be met at the same time: each tank must be rated at more than 119 gallons and the tanks together must total 1,000 gallons or more, whether they are permanently or temporarily attached to the vehicle or chassis. The endorsement exists because tanks of that size create liquid surge and a high center of gravity, not because of what the tank happens to hold.
Source: 49 CFR 383.5 (definition of "tank vehicle"); AAMVA Model CDL Manual Sec. 8 introductionReport a problem with this question
2. A driver hauls raw milk in a permanently mounted 6,000-gallon tank. Milk is not a hazardous material. Is the tank vehicle (N) endorsement required?
- A.Yes — the liquid does not have to be a hazardous material for the endorsement to apply✓ Answer
- B.No — the endorsement applies only to hazardous liquids and liquid gases
- C.No — food-grade products are exempt from all endorsement requirements
- D.Only if the vehicle is also required to display placards
The tank vehicle definition turns on how the cargo is carried — a liquid or liquid gas in bulk tanks that meet the capacity thresholds — not on whether the cargo is hazardous. Water, milk and juice tankers surge and roll over the same way fuel tankers do, so they require the same endorsement.
Source: 49 CFR 383.5; AAMVA Model CDL Manual Sec. 8 introductionReport a problem with this question
3. During the inspection of any tank vehicle, which single item is the most important to check?
- A.The mounting height of the fifth wheel
- B.Leaks✓ Answer
- C.The paint and lettering on the tank shell
- D.Steering-axle tire tread depth
Leaks are the top inspection priority on every tank vehicle: you must look under and around the vehicle before loading, unloading or driving. Hauling a liquid or gas in a leaking tank is a crime — you can be cited, stopped from driving further, and held liable for the cost of cleaning up the spill.
Source: AAMVA Model CDL Manual Sec. 8.1.1Report a problem with this question
4. What must you confirm about manhole covers and vents when inspecting a tank vehicle?
- A.The vents are taped over whenever the tank is more than half full
- B.The covers have gaskets and close correctly, and the vents are clear so they can work✓ Answer
- C.The covers are left slightly open so pressure can escape while driving
- D.The covers are welded shut and the vents are plugged to keep odors in
A missing or damaged gasket lets product escape, and a blocked vent stops the tank from equalizing pressure, which can collapse or rupture the shell. That is why the inspection requires intact gaskets, properly closing covers and unobstructed vents before loading, unloading or moving the vehicle.
Source: AAMVA Model CDL Manual Sec. 8.1.1Report a problem with this question
5. You finish loading and notice that one discharge valve is still open and a manhole cover is not latched. What is the correct action?
- A.Leave them open so the load can breathe, but reduce your speed
- B.Drive slowly to the next stop and close them there
- C.Move the vehicle only if the tank is less than half full
- D.Close and secure all valves and manhole covers before the vehicle is moved at all✓ Answer
A tank vehicle must never be driven with open valves or open manhole covers, because product can spill out on the first turn or stop and the surging load is no longer contained. The same pre-trip check must confirm that special-purpose equipment — vapor recovery kits, grounding and bonding cables, the emergency shut-off system and any built-in fire extinguisher — is present and working.
Source: AAMVA Model CDL Manual Secs. 8.1.2-8.1.3; 49 CFR 383.119(g)Report a problem with this question
6. Testing has shown what about tank vehicles and the speed posted for a curve?
- A.Posted curve speeds apply only to cars; trucks may add 5 mph
- B.A tank vehicle can roll over at the posted speed, so curves and ramps must be taken well below it✓ Answer
- C.The posted speed already includes a safety margin for tank vehicles
- D.A tanker is safe at the posted speed as long as the tank is completely full
Much of a tank load's weight rides high above the road, so the vehicle is top-heavy and rolls easily, and tests have shown tankers turning over at the speed posted for the curve. Posted curve and ramp speeds are set for ordinary vehicles, so a tank driver has to slow well below them.
Source: AAMVA Model CDL Manual Secs. 8.2.1 and 8.3.3Report a problem with this question
7. What are the two reasons a tank vehicle needs special care behind the wheel?
- A.A high center of gravity and the movement of the liquid (surge)✓ Answer
- B.Air brake lag and a shorter trailer
- C.Placarding rules and log book limits
- D.A longer wheelbase and heavier tires
Both hazards come from carrying liquid in bulk: the load's weight sits high, which makes the vehicle top-heavy, and the liquid is free to move inside the tank, pushing the vehicle whenever you start, stop or turn. Every tank-driving technique — smooth inputs, slow curves, extra following distance — is aimed at one of these two problems.
Source: AAMVA Model CDL Manual Secs. 8.2.1-8.2.2Report a problem with this question
8. You have brought a partially loaded tanker to a complete stop at an icy intersection. Why can the load still move the truck?
- A.The liquid freezes and expands, pushing the tank ahead
- B.Air pressure trapped in the vents drives the vehicle forward
- C.The surging wave of liquid can shove the stopped truck out into the intersection✓ Answer
- D.Tank vehicles lose all parking brake holding power when loaded
In a partly filled tank the liquid keeps sloshing after the vehicle has stopped, and when the wave strikes the end of the tank it pushes the truck in the direction the wave is moving. On ice there is almost no traction to resist that push, so a fully stopped vehicle can be shoved forward into cross traffic.
Source: AAMVA Model CDL Manual Sec. 8.2.2Report a problem with this question
9. Which braking habits help control liquid surge when bringing a tank vehicle to a stop?
- A.Pump the brakes rapidly all the way to the stop
- B.Use only the trailer hand valve so the tractor brakes stay free
- C.Release the brakes just before stopping so the surge can settle
- D.Brake far in advance, keep steady pressure on the brakes, and do not release them too soon✓ Answer
Early, steady braking keeps the liquid from building one large wave, and holding pressure until the vehicle is completely stopped keeps the returning surge from pushing you forward. Releasing too soon lets that wave move the vehicle, and increasing your following distance is what gives you room to brake this gently.
Source: AAMVA Model CDL Manual Sec. 8.3.2Report a problem with this question
10. What do bulkheads do inside a cargo tank, and what must the driver watch because of them?
- A.They divide the tank into separate smaller compartments, so weight distribution front to rear must be watched✓ Answer
- B.They vent the tank to the atmosphere so no outage is needed
- C.They are heating coils that keep dense liquids flowing
- D.They are perforated plates that eliminate all forward-and-back surge
Bulkheads are solid divisions that create separate tanks within the tank, so filling or emptying one compartment at a time changes how the load sits over the axles. Because of that, the driver must avoid putting too much weight on the front or the rear of the vehicle when loading and unloading.
Source: AAMVA Model CDL Manual Sec. 8.2.3Report a problem with this question
11. How do baffles differ from bulkheads, and which surge do they control?
- A.Baffles seal each compartment completely, eliminating all surge
- B.Baffles are external ribs that stiffen the shell and do not affect the liquid
- C.Baffles are bulkheads with holes; they slow forward-and-back surge, but side-to-side surge still occurs✓ Answer
- D.Baffles are solid walls; they stop side-to-side surge but not forward-and-back surge
The holes in a baffle let liquid pass through only slowly, which damps the front-to-back wave created by starting and stopping. Liquid can still wash across the width of the tank, so side-to-side surge remains — and that is the movement most likely to roll the vehicle over.
Source: AAMVA Model CDL Manual Sec. 8.2.4Report a problem with this question
12. Why are tanks that haul food products such as milk usually smooth bore (un-baffled)?
- A.Sanitation regulations forbid baffles because a baffled interior is too hard to clean✓ Answer
- B.Smooth bore tanks control surge better than baffled tanks
- C.Baffles would freeze the product in cold weather
- D.Food products are too dense for baffles to hold back
Baffles create surfaces and corners that cannot be washed and sanitized reliably, so sanitation rules for food-grade tanks require a smooth interior. The trade-off is that nothing slows the liquid down, so forward-and-back surge is very strong and the driver must start and stop extremely gradually.
Source: AAMVA Model CDL Manual Sec. 8.2.5Report a problem with this question
13. In a baffled tank, which liquid movement is the one most likely to cause a rollover?
- A.Movement of the vapor above the liquid
- B.Forward-and-back surge
- C.Side-to-side surge✓ Answer
- D.Vertical expansion of the liquid as it warms
Baffles have holes that damp the front-to-back wave, but they do nothing to stop liquid from washing across the width of the tank. Since a tanker is already top-heavy, that sideways shift of weight is what tips the vehicle, especially in curves, on ramps and during quick lane changes.
Source: AAMVA Model CDL Manual Sec. 8.2.4Report a problem with this question
14. What is "outage," and why must it be left in a cargo tank?
- A.The empty space left above the load, because liquids expand as they warm✓ Answer
- B.The amount of product lost to leaks during a trip
- C.The unusable liquid left below the discharge valve
- D.The time a tank is out of service for periodic retesting
Liquids take up more volume as their temperature rises, so a tank filled completely could be over-pressurized or force product out through vents and fittings. Different liquids expand by different amounts, which is why the driver must know the outage required for the specific product being hauled.
Source: AAMVA Model CDL Manual Sec. 8.2.6Report a problem with this question
15. Which three things determine how much liquid you may load into a cargo tank?
- A.The number of baffles, the tank's color, and the outside temperature
- B.How much the liquid will expand in transit, the weight of the liquid, and legal weight limits✓ Answer
- C.Trip length, the driver's hours of service, and tire pressure
- D.The tank's retest date, the placard type, and the size of the discharge hose
Expansion sets the outage you must leave, the liquid's weight decides how many gallons fit under the axle and gross limits, and the legal limits themselves cap the total. All three have to be satisfied at once, so whichever is most restrictive is what governs the load.
Source: AAMVA Model CDL Manual Sec. 8.2.7Report a problem with this question
16. You are hauling a dense liquid such as an acid. Why is the tank often only partly filled, and what does that cause?
- A.Partial loads are required so that the baffles can be inspected in transit
- B.A full load would freeze, and a partial load puts the center of gravity below the axles
- C.Dense liquids need extra vapor space for placarding, which removes surge
- D.A full load would exceed legal weight limits, and the partial load increases surge✓ Answer
Heavy liquids reach the legal gross and axle weight limits long before the tank is physically full, so the tank can only be loaded part way. The unavoidable side effect is more empty space for the liquid to move in, so surge is stronger and starts, stops and turns must be even smoother.
Source: AAMVA Model CDL Manual Sec. 8.2.7Report a problem with this question
17. What is the correct technique for taking a curve in a tank vehicle?
- A.Slow down before entering the curve, then accelerate slightly through it✓ Answer
- B.Brake steadily from the entry of the curve all the way to the exit
- C.Enter at the posted speed and brake hard at the middle of the curve
- D.Coast through with the clutch in so the drive wheels cannot spin
Braking inside the curve throws weight onto the front axle and lets the liquid surge sideways while the tires are already using their traction to turn, which invites a skid or a rollover. Slowing first and then applying slight power keeps the vehicle settled through the turn — and remember the posted speed itself is often too fast for a tanker.
Source: AAMVA Model CDL Manual Sec. 8.3.3Report a problem with this question
18. Which statement about stopping distance for tank vehicles is correct?
- A.Wet roads double the normal stopping distance, and an empty tank vehicle may take longer to stop than a full one✓ Answer
- B.A loaded tanker always needs exactly the same distance as an empty one
- C.Wet roads have no measurable effect once the tank is baffled
- D.Empty tank vehicles always stop in half the distance that full ones need
A wet surface cuts the traction available to the tires, roughly doubling the distance needed to stop. An empty tank has less weight pressing the tires onto the road and its brakes and suspension are designed for a loaded vehicle, so the empty rig may actually require more distance — a point many drivers get backward.
Source: AAMVA Model CDL Manual Sec. 8.3.4Report a problem with this question
19. The wheels of your tank trailer begin to skid on a slick road. What should you do?
- A.Accelerate hard to pull the trailer back into line
- B.Take action to restore traction to the wheels rather than braking the trailer with the hand valve✓ Answer
- C.Apply the trailer hand valve firmly to straighten the rig
- D.Steer sharply the other way while braking hard
A skid means the tires have lost their grip, so the fix is whatever restores traction — easing off the brakes or the throttle — before you correct with steering. Braking the trailer alone with the hand valve, over-accelerating, or steering quickly while braking all make it worse and can jackknife or roll a tank vehicle.
Source: AAMVA Model CDL Manual Sec. 8.3.5 (see also skid control, Sec. 2.17)Report a problem with this question
20. A driver hauls gasoline in a 9,000-gallon cargo tank that must display placards. Which set of credentials and markings applies?
- A.Only the hazardous materials (H) endorsement, because placards take the place of the tank endorsement
- B.No endorsement is needed as long as placards are displayed and the driver holds a Class A CDL
- C.Both the tank vehicle (N) and hazardous materials (H) endorsements — issued together as the X endorsement — plus the required placards✓ Answer
- D.Only the tank vehicle (N) endorsement, because the tank is the reason for the placards
The two endorsements cover different risks: N covers handling bulk liquid (surge and a high center of gravity) and H covers the hazardous material itself, so a placarded bulk-liquid load requires both. When they are issued together the license shows the combined X endorsement, and the placarding requirements still apply on their own terms.
Source: 49 CFR 383.93(b) (endorsement types, including X = N + H); AAMVA Model CDL Manual Secs. 8 and 9Report a problem with this question

Practice questions based on the AAMVA/FMCSA model CDL manual. Requirements vary by state — study your state's official CDL manual before your exam. Official CDL info →

1. Federal rules require a tank vehicle (N) endorsement when a driver hauls a liquid or liquid gas in tanks meeting which rated-capacity thresholds?

2. A driver hauls raw milk in a permanently mounted 6,000-gallon tank. Milk is not a hazardous material. Is the tank vehicle (N) endorsement required?

3. During the inspection of any tank vehicle, which single item is the most important to check?

4. What must you confirm about manhole covers and vents when inspecting a tank vehicle?

5. You finish loading and notice that one discharge valve is still open and a manhole cover is not latched. What is the correct action?

6. Testing has shown what about tank vehicles and the speed posted for a curve?

7. What are the two reasons a tank vehicle needs special care behind the wheel?

8. You have brought a partially loaded tanker to a complete stop at an icy intersection. Why can the load still move the truck?

9. Which braking habits help control liquid surge when bringing a tank vehicle to a stop?

10. What do bulkheads do inside a cargo tank, and what must the driver watch because of them?

11. How do baffles differ from bulkheads, and which surge do they control?

12. Why are tanks that haul food products such as milk usually smooth bore (un-baffled)?

13. In a baffled tank, which liquid movement is the one most likely to cause a rollover?

14. What is "outage," and why must it be left in a cargo tank?

15. Which three things determine how much liquid you may load into a cargo tank?

16. You are hauling a dense liquid such as an acid. Why is the tank often only partly filled, and what does that cause?

17. What is the correct technique for taking a curve in a tank vehicle?

18. Which statement about stopping distance for tank vehicles is correct?

19. The wheels of your tank trailer begin to skid on a slick road. What should you do?

20. A driver hauls gasoline in a 9,000-gallon cargo tank that must display placards. Which set of credentials and markings applies?