22 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. Under the federal CDL rules, when must a driver hold the N (tank vehicle) endorsement?
- A.When hauling liquid in any tank with an individual rated capacity over 50 gallons, whatever aggregate total is carried on the trip
- B.When hauling liquid in a tank of any rated capacity, and the shipping paper shows the material as hazardous on that run
- C.When hauling liquid in a tank with an aggregate capacity over 3,000 gallons, however the individual tanks happen to be rated
- D.When hauling liquid in a tank with an individual rated capacity over 119 gallons and an aggregate of 1,000 gallons or more✓ Answer
49 CFR 383.5 defines a tank vehicle by capacity alone: each tank must have an individual rated capacity of more than 119 gallons and the tanks must total 1,000 gallons or more. Because the trigger is capacity and not hazard, the endorsement can be required for a completely harmless liquid.
Source: 49 CFR 383.5 (definition of "tank vehicle"); 49 CFR 383.93(b)(3)Report a problem with this question
2. A driver hauls only milk in a 6,000-gallon tank trailer. Is the tank vehicle endorsement required?
- A.No, the load carries no placards, and the endorsement requirement always follows the placarding rules
- B.No, milk is a food product, and tanks built for food products are exempt from the endorsement
- C.Yes, the requirement rests on the tank's rated capacity, not on whether the liquid is hazardous✓ Answer
- D.Yes, but only while the tank trailer is permanently mounted and not set on the frame for one trip
The definition in 49 CFR 383.5 turns on rated capacity, so a non-hazardous food product such as milk falls under it just as gasoline does. A 6,000-gallon tank easily clears both the 119-gallon individual and 1,000-gallon aggregate figures, so the N endorsement applies.
Source: 49 CFR 383.5 (definition of "tank vehicle"); 49 CFR 383.93(b)(3)Report a problem with this question
3. Two 800-gallon portable tanks of liquid are chained to a flatbed for a single trip. How does the endorsement rule treat them?
- A.They do not count, because neither tank by itself reaches the 1,000-gallon figure the rule applies to a container
- B.They count only if piping joins the two tanks so the liquid can move between them while the vehicle is moving
- C.They count, because the rule covers tanks attached temporarily as well as permanently, and together they exceed 1,000 gallons✓ Answer
- D.They do not count, because portable tanks strapped to a deck are treated as freight rather than as part of the vehicle
49 CFR 383.5 says the tanks may be "either permanently or temporarily attached" to the vehicle or chassis, and the 1,000-gallon test is an aggregate of all the tanks. Each 800-gallon tank is over 119 gallons and the two together are 1,600 gallons, so the endorsement is required.
Source: 49 CFR 383.5 (definition of "tank vehicle": permanently or temporarily attached)Report a problem with this question
4. What is the most important thing to look for when inspecting a tank vehicle?
- A.Tread depth, measured with a gauge in every major groove of the steer tires and the trailer tires
- B.Placard placement, confirmed on all four sides and turned 45 degrees so each sits on point
- C.Leaks, checked under and around the tank shell, its valves, pipes and connections✓ Answer
- D.Brake lining wear, judged by pulling each slack adjuster by hand and measuring its travel
The model CDL manual's tank section states that leaks are the single most important item, because a driver may not legally operate a leaking cargo tank at all. Tires, brakes and placards still matter, but a leak stops the trip before it starts.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Inspecting Tank Vehicles)Report a problem with this question
5. Inspecting the top of a cargo tank, what must the driver confirm about the manhole covers and the vents?
- A.That the covers have their gaskets and close correctly, and that the vents are clear and not clogged✓ Answer
- B.That the covers are welded shut and the vents plugged, so nothing can escape while the tank is in motion
- C.That the covers sit slightly open and the vents are removed, so pressure can escape freely as the load warms up
- D.That the covers carry the rated capacity stamp and the vents show the identification number of the liquid
The manual's tank inspection list requires that manhole covers have gaskets and close properly and that vents are kept clear. A clogged vent lets pressure or vacuum build inside the shell as the liquid heats or is drawn off, which can damage the tank or force product out.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Inspecting Tank Vehicles: manhole covers and vents)Report a problem with this question
6. After loading, you find a discharge valve open and one manhole cover unlatched. What should you do?
- A.Note both items on the post-trip inspection report and correct them once the load has been delivered
- B.Close the valve and latch the cover before the vehicle moves, then check both again at the first stop✓ Answer
- C.Leave the valve open to relieve pressure and secure only the cover, since venting prevents a rupture in transit
- D.Drive slowly to the nearest scale and have the operator witness the valve being closed there
An open discharge valve or an unlatched cover is a spill waiting to happen, and federal rules bar operating a vehicle likely to cause an escape of cargo. The defect must be corrected before the wheels turn, and the manual tells drivers to re-check valves and covers during the trip as well.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Inspecting Tank Vehicles); 49 CFR 392.9(a)Report a problem with this question
7. Which pair of characteristics makes a tank vehicle harder to handle than most other commercial vehicles?
- A.A high center of gravity together with the surge of the liquid moving inside the shell✓ Answer
- B.A short wheelbase together with the extra wind drag of the round tank shell
- C.A high center of gravity together with the lag built into the air brake lines
- D.A low center of gravity together with extra weight riding on the steering axle
The manual names two problems unique to tanks: a high center of gravity, because much of the weight rides well above the road, and liquid surge, because the load itself moves. Together they make the vehicle easy to roll over and hard to stop or steer smoothly.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Driving Tank Vehicles: high center of gravity and liquid surge)Report a problem with this question
8. A curve carries a posted advisory speed of 40 mph. How should the driver of a loaded tank vehicle treat that sign?
- A.Slow to well below 40 mph before the curve, since advisory speeds are set for cars✓ Answer
- B.Hold a steady 40 mph through the whole curve, since advisory speeds already allow for heavy vehicles
- C.Enter above 40 mph so that momentum carries the load through before it can shift sideways
- D.Enter at 40 mph and brake steadily inside the curve to hold the liquid toward the rear head
Posted advisory speeds are calculated for passenger cars, which have a low center of gravity and a load that does not move. A tank vehicle with a high center of gravity and liquid surge can roll at the posted figure, so the manual tells tank drivers to take curves well below it.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Driving Tank Vehicles: curves and posted speeds)Report a problem with this question
9. What is the correct technique for taking a curve in a tank vehicle?
- A.Brake firmly all the way through the curve and accelerate only past the exit
- B.Hold a steady speed into the curve and then shift to a lower gear at its midpoint
- C.Slow down before entering the curve, then accelerate gently once you are in it✓ Answer
- D.Coast into the curve out of gear so the drive wheels cannot push the tank out
Braking or shifting inside a curve throws the liquid sideways and unsettles a high-riding load just when the tires are already working hardest. Slowing first and then adding gentle throttle keeps the rig stable and pushes the vehicle through the turn under control.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Driving Tank Vehicles: curves)Report a problem with this question
10. You have stopped a partly loaded smooth-bore tanker at a red light. What can liquid surge do?
- A.Raise tank pressure enough to open the safety relief vent on top of it
- B.Pull the vehicle backward and lock its drive wheels until the liquid settles
- C.Lift the steering axle clear of the road for a moment after every stop
- D.Push the vehicle forward after it has fully stopped, out into the intersection✓ Answer
In a smooth-bore tank nothing slows the liquid, so it keeps travelling forward after the vehicle has stopped and slams into the front head. The manual warns that this wave of moving weight can shove a stopped truck out into an intersection.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Liquid Surge; un-baffled smooth bore tanks)Report a problem with this question
11. Which habit does most to limit the effect of liquid surge on a tank vehicle?
- A.Pumping the brake pedal on the approach so the liquid stops in a series of steps
- B.Shifting to neutral before each stop so engine drag cannot add to the forward surge
- C.Braking hard and late, using the trailer hand valve to settle the load just before stopping
- D.Braking smoothly and early, keeping enough following distance that hard stops are rare✓ Answer
Surge is driven by sudden changes in speed, so the cure is to change speed gradually, which requires space to work in. The manual also warns that the trailer hand valve is a testing device only and must never be used to slow or hold a rig, because it can overheat or skid the trailer.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Driving Tank Vehicles); Combination Vehicles section (trailer hand valve)Report a problem with this question
12. How do bulkheads differ from baffles inside a cargo tank?
- A.Bulkheads are the outside rollover rails, while baffles are the vents fitted on top of the shell
- B.Bulkheads are solid walls dividing the tank into compartments, while baffles are perforated✓ Answer
- C.Bulkheads are the manhole covers themselves, while baffles are the internal product piping
- D.Bulkheads are perforated walls inside one compartment, while baffles divide the whole tank into sections
Bulkheads are solid dividers that create separate compartments, which is why a compartmented tank can carry different products or be loaded to balance weight. Baffles are bulkheads with holes in them: the liquid passes through, but more slowly, which damps the wave.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Bulkheads and Baffled Tanks)Report a problem with this question
13. In a baffled tank, which liquid movement do the baffles control and which do they not?
- A.They cut down both motions equally, so a baffled tank handles like a dry van
- B.They cut down forward-and-back surge, but they do little about side-to-side surge✓ Answer
- C.They cut down side-to-side surge, but they do little about forward-and-back
- D.They cut down surge only while full, and do nothing on a partly loaded tank
Baffles are vertical walls set across the tank, so they stand in the way of liquid travelling lengthwise but not of liquid moving across the shell. That is why a baffled tank is much calmer under braking yet still rolls easily in a turn.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Baffled Tanks)Report a problem with this question
14. Why are tanks that haul milk and other food products normally built without baffles?
- A.Sanitation rules apply, and the inside of a baffled tank is too hard to clean✓ Answer
- B.Baffles would let the product freeze against the tank walls in cold-weather hauling
- C.A smooth-bore shell lets a greater volume be loaded within the same legal weight
- D.Food liquids are so light that baffles would make no difference to the handling
Sanitation regulations for food transport require a shell that can be washed out completely, and baffles create pockets and seams that cannot be cleaned reliably. The trade-off is that these smooth-bore tanks give the strongest forward-and-back surge of all.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Un-baffled / smooth bore tanks)Report a problem with this question
15. In a baffled tank, which liquid movement poses the greater rollover threat?
- A.Backward movement under acceleration, which the baffles load onto the rear axle
- B.Forward movement into the front head, which the baffles gather at the nose
- C.Upward sloshing against the walls as the tank crosses rough or broken road
- D.Side-to-side movement, which the baffles do not restrain, above all in turns✓ Answer
Baffles are set crosswise, so they do nothing to stop liquid sliding toward one side of the shell. When that weight shifts outward in a turn on top of an already high center of gravity, the rig can go over, which is why the manual singles out side-to-side surge as the rollover danger.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Baffled Tanks: side-to-side surge and rollover)Report a problem with this question
16. Why must a driver leave outage — empty space — when loading a cargo tank?
- A.Liquids expand as they warm up, and a completely full tank leaves no room✓ Answer
- B.The vapor given off by the product has to be recovered in that space
- C.Air at the top cushions the surge and stops the load moving in turns
- D.Loose liquid at the top keeps the load's center of gravity lower
Liquids take up more room as their temperature rises, and a tank loaded to the brim in cool weather has nowhere for that extra volume to go. Outage is the deliberate empty space left for expansion, and different liquids expand by different amounts, so the required outage varies.
Source: AAMVA Model CDL Manual, Tank Vehicles section (Outage)Report a problem with this question
17. Which three factors together decide how much liquid may be loaded into a cargo tank?
- A.The pump's flow rate, the weight of the liquid, and the width of the loading hose
- B.The amount the liquid will expand, the weight of the liquid, and legal weight limits✓ Answer
- C.The number of baffles fitted, the length of the trip, and the rating of the steer tires
- D.The size of the manhole, the outside air temperature, and the material of the shell
The manual lists three limits on how much you may load: the outage needed for expansion, the weight of the particular liquid, and the legal weight limits for the vehicle and its axles. Whichever limit is reached first is the one that controls the load.
Source: AAMVA Model CDL Manual, Tank Vehicles section (How Much to Load)Report a problem with this question
18. A dense liquid such as an acid brings the tank to its legal weight while the shell is only part full. What follows from that?
- A.The part-full shell means the outage requirement no longer applies to that load
- B.The part-full shell ends surge, because the liquid cannot climb the tank walls
- C.The part-full shell lowers the center of gravity enough to remove any rollover risk
- D.The part-full shell allows strong surge, so braking and steering must stay gentle✓ Answer
Surge needs room to develop, and a shell that is only partly filled gives the liquid the most room to run. A heavy product therefore produces the worst handling of all: legal on the scale, but with a load that slams forward at every stop and sideways in every turn.
Source: AAMVA Model CDL Manual, Tank Vehicles section (How Much to Load: weight of the liquid)Report a problem with this question
19. How does an empty tank vehicle compare with a loaded one in stopping distance?
- A.The empty tank may need a longer distance, since light axles have less traction✓ Answer
- B.The empty tank needs the same distance, as brakes are sized for the load
- C.The empty tank stops shorter on wet roads and longer on dry pavement
- D.The empty tank always stops shorter, simply because it weighs far less
Braking power depends on the grip between tire and road, and an empty rig presses its tires down with far less force. With stiff suspension and brakes sized for a loaded weight, the wheels lock and bounce easily, so an empty tank can take longer to stop than a full one.
Source: AAMVA Model CDL Manual, Speed Management (empty vehicles and traction); Tank Vehicles sectionReport a problem with this question
20. The wheels of your tank trailer begin to skid while you are braking. What should you do?
- A.Steer sharply toward the skid and hold the brakes until the trailer settles down
- B.Release the brakes to let the wheels roll again, then slow with light pressure✓ Answer
- C.Apply the trailer hand valve alone so that only the trailer brakes stay on
- D.Press the brakes harder to pull the trailer back in line behind the tractor
A locked wheel has almost no sideways grip, which is exactly why the trailer swings out. Releasing the brakes lets the wheels turn again and restores traction so the trailer can follow the tractor; braking harder or using the hand valve only keeps the wheels locked.
Source: AAMVA Model CDL Manual, Combination Vehicles section (trailer jackknife / trailer skid)Report a problem with this question
21. A driver hauls 8,000 gallons of gasoline in a cargo tank. Which credentials does the job require?
- A.A CDL carrying the hazardous materials endorsement by itself, since the hazard governs
- B.A CDL carrying the doubles/triples and tank endorsements, as fuel delivery requires
- C.A CDL carrying both the tank and hazardous materials endorsements, combined as the X endorsement✓ Answer
- D.A CDL carrying the tank endorsement by itself, since a tank is what the load rides in
Gasoline in a large cargo tank triggers both rules at once: the tank endorsement because of the capacity, and the hazardous materials endorsement because the load is placarded. 49 CFR 383.93 provides the X endorsement as the single code that covers both, and the hazmat side also requires a TSA security threat assessment.
Source: 49 CFR 383.93(b)(3) and (b)(4) (tank and hazardous materials endorsements; combined X endorsement)Report a problem with this question
22. Before leaving, you find liquid dripping from a valve on your loaded cargo tank. What does the rule require?
- A.Catch the drip in a container and go on, emptying the container at every rest stop
- B.Keep the vehicle parked; a leaking tank must be repaired before the trip starts✓ Answer
- C.Deliver the load first, since the product is going to be unloaded at the terminal anyway
- D.Drive at reduced speed to the nearest repair shop and report the leak on arrival
The manual states flatly that it is never acceptable to drive a leaking tank, and for hazardous cargo 49 CFR 177.854 forbids moving a leaking package at all. A driver who moves one can be cited, placed out of service and held responsible for the cost of the cleanup.
Source: 49 CFR 177.854(a) (no movement of leaking packages); AAMVA Model CDL Manual, Tank Vehicles section (Inspecting Tank Vehicles)Report 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 →