Practice questions written from the official CDL manual. Correct answers and explanations are shown below each question. (Turn on JavaScript for the interactive practice and exam-simulation modes.)
1. What generally defines a 'tank vehicle' that requires a tank endorsement?
- AA vehicle hauling liquid or liquid gas in a tank with an individual rated capacity of more than 119 gallons and an aggregate of 1,000 gallons or moreCorrect
- BAny truck that carries hazardous materials of any kind
- CAny vehicle with a trailer longer than 40 feet
- DA vehicle that carries only dry bulk cargo like grain or sand
Why: A tank endorsement is required to haul a liquid or liquid gas in a tank (or tanks) with an individual rated capacity of more than 119 gallons and a combined (aggregate) capacity of 1,000 gallons or more. The cargo does not have to be hazardous for this rule to apply.
Based on: CDL Manual §8 — Tank Vehicles (Endorsement Requirements)
2. What is 'liquid surge' in a tank vehicle?
- AA sudden spike in engine oil pressure
- BThe buildup of vapor pressure inside a sealed tank
- CThe back-and-forth or side-to-side movement of liquid in a partially filled tankCorrect
- DA surge of electrical current from the trailer lights
Why: Liquid surge is the wave-like movement of liquid inside a partially filled tank. When the vehicle changes speed or direction, the liquid keeps moving, which can strongly affect how the vehicle handles.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Liquid Surge)
3. Why are tank vehicles especially likely to roll over?
- AThey have a high center of gravity because the liquid load sits up highCorrect
- BTheir tires are always underinflated
- CThey are lighter than other commercial vehicles
- DThey have no brakes on the trailer axles
Why: Tank vehicles carry a lot of weight up high, giving them a high center of gravity. This makes them top-heavy and easy to tip. Tests show tankers can roll over at the speeds posted for curves, so drivers must slow well below those limits.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (High Center of Gravity)
4. When a tank truck comes to a stop, how can a strong forward liquid surge affect it?
- AIt pulls the truck backward and stalls the engine
- BIt has no effect once the brakes are applied
- CIt can push the truck forward, for example into an intersectionCorrect
- DIt automatically locks the trailer brakes
Why: As the truck slows, the liquid wave surges forward and hits the front of the tank. This push can shove the vehicle in the direction the wave is moving, sometimes pushing a stopped truck out into an intersection. It is especially dangerous on slippery roads.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Liquid Surge)
5. What are bulkheads in a liquid tank?
- ARubber seals around the manhole cover
- BThe metal steps used to climb on top of the tank
- CVents that release vapor pressure
- DSolid walls that divide a large tank into several smaller separate tanksCorrect
Why: Bulkheads are solid dividers that split one large tank into several smaller tank sections. Because each section is separate, the driver must pay attention to how the load is spread out for proper weight balance front to back.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Types of Tanks)
6. What is a baffled tank?
- AA tank with no internal dividers at all
- BA tank made only for dry bulk cargo
- CA tank cooled by an external refrigeration unit
- DA tank with bulkheads that have holes, letting liquid flow through while slowing surgeCorrect
Why: Baffled tanks have bulkheads with holes in them. The holes let liquid pass from one part of the tank to another but slow the liquid down. This helps control the forward-and-back surge as the vehicle speeds up or slows down.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Baffled Tanks)
7. Which surge do baffles in a baffled tank do little to prevent?
- AForward-and-back surge
- BSide-to-side surgeCorrect
- CVapor pressure surge
- DSurge caused by braking
Why: Baffles help control forward-and-back surge, but they do little to stop side-to-side surge. Side-to-side movement of the liquid can still cause a rollover, so drivers of baffled tanks must steer and corner smoothly.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Baffled Tanks)
8. What is an unbaffled (smooth bore) tank?
- AA tank with baffles every few feet
- BA tank with no bulkheads or baffles inside at allCorrect
- CA tank divided into three separate compartments
- DA tank used only for compressed gas
Why: An unbaffled or 'smooth bore' tank has nothing inside to slow the liquid. These are often used to haul food products like milk, because baffles are hard to keep clean and sanitary. Without baffles, the forward-and-back surge is very strong.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Unbaffled Tanks)
9. Why do many tanks that haul milk and other food products have smooth bores (no baffles)?
- ABaffles make the tank too heavy to be legal
- BSanitation rules make baffles hard to clean, so smooth bores keep food products cleanCorrect
- CSmooth bore tanks are cheaper to build only for gasoline
- DBaffles are illegal on any food tanker
Why: Baffles have many surfaces that are hard to clean. Because food products like milk must be kept sanitary, these tanks are usually smooth bore with no baffles. The trade-off is that surge is very strong, so the driver must be extra careful.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Unbaffled Tanks)
10. What is 'outage' when loading a liquid tank?
- AThe time a tank spends empty between loads
- BA power failure at the loading terminal
- CThe empty space left at the top of the tank to allow the liquid room to expandCorrect
- DThe amount of liquid that leaks out during transport
Why: Outage is the empty space you leave at the top of a tank. Liquids expand as they warm up, so you must leave room for that expansion. Filling a tank completely with a warming liquid could cause it to overflow or burst.
Based on: CDL Manual §8.3 — Safe Driving Rules (Outage)
11. Why must you leave outage (extra space) in a liquid tank instead of filling it to the top?
- ABecause liquids expand as they warm and need room to growCorrect
- BBecause a full tank is illegal in every state
- CBecause the vapor must be pumped out first
- DBecause the tank is weighed only when half full
Why: Liquids expand (take up more space) as their temperature rises. If a tank were filled completely, the expanding liquid would have nowhere to go and could overflow or damage the tank. Different liquids expand different amounts, so they need different outage.
Based on: CDL Manual §8.3 — Safe Driving Rules (Outage)
12. Do all liquids require the same amount of outage?
- AYes, exactly 10 percent for every liquid
- BNo, but only water needs any outage at all
- CYes, all liquids need the same fixed space
- DNo, different liquids expand by different amounts and need different outageCorrect
Why: Different liquids expand by different amounts as they warm, so they require different amounts of outage. That is one reason a driver must know what is being hauled and how much room to leave.
Based on: CDL Manual §8.3 — Safe Driving Rules (Outage)
13. Besides outage, what three things must you consider to figure out how much liquid to load in a tank?
- ATire brand, engine size, and paint color
- BThe weather forecast, the driver's weight, and fuel price
- CThe amount the liquid will surge, the driver's schedule, and the tank's age
- DLegal weight limits, the weight (density) of the liquid, and the amount that will surgeCorrect
Why: To decide how much to load you must consider: how much the liquid will expand (outage), the legal weight limits, and how heavy the liquid is. A dense, heavy liquid may reach the legal weight limit before the tank is anywhere near full.
Based on: CDL Manual §8.3 — Safe Driving Rules (How Much Can You Load?)
14. Why might a tank carrying a very heavy (dense) liquid, such as some acids, be only partly full?
- ABecause the liquid reaches the legal weight limit before the tank is fullCorrect
- BBecause acids cannot be hauled in a full tank by law
- CBecause a half-empty tank surges less than a full one
- DBecause dense liquids evaporate too quickly to keep the tank full
Why: Some liquids are so heavy (dense) that a full tank would be over the legal weight limit. To stay legal, the driver loads only enough to meet the weight limit, which may leave the tank far from full.
Based on: CDL Manual §8.3 — Safe Driving Rules (How Much Can You Load?)
15. How should you use the brakes when driving a loaded tank vehicle?
- AWait until the last moment, then brake as hard as possible
- BPump the brakes rapidly to keep the liquid still
- CBrake smoothly and far in advance of a stop, and increase your following distanceCorrect
- DCoast in neutral and use only the parking brake
Why: Because of surge and the high center of gravity, tank drivers should start braking far ahead of a stop, apply the brakes smoothly, and keep extra following distance. Sudden, hard braking can cause surge or a skid.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Smooth Driving / Braking)
16. How should you handle starts, stops, turns, and lane changes in a tank vehicle?
- AMake them as quickly as possible to save time
- BMake them gently and smoothly to avoid setting the liquid movingCorrect
- COnly worry about smoothness when the tank is completely full
- DUse hard steering inputs so the trailer follows tightly
Why: Smooth driving keeps the liquid from surging. Make gentle starts, stops, turns, and lane changes. Sudden or jerky moves can start the liquid surging, which can pull the vehicle off course or cause a rollover.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Smooth Driving)
17. How should you take a curve or exit ramp in a loaded tank vehicle?
- AAt the posted speed limit for the curve, since it is set for all vehicles
- BFaster than posted so surge does not build up
- CWell below the posted speed, because tankers can roll over at those speedsCorrect
- DAt any speed, as long as the tank has baffles
Why: Posted curve speeds are set for ordinary vehicles. Because a tanker is top-heavy, it can roll over at the posted speed. Slow down well below the posted limit before entering the curve, then accelerate gently through it.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Curves)
18. Compared with other vehicles, how much following distance should a tank vehicle keep?
- ALess distance, because tankers stop quickly
- BThe same distance as a passenger car
- CNo extra distance is needed if the tank is baffled
- DMore distance, because a loaded tank needs extra room to stop safelyCorrect
Why: A loaded tank vehicle is heavy, top-heavy, and affected by surge, so it needs more room to stop. Drivers should increase their following distance and brake early to allow for a safe, smooth stop.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Following Distance)
19. When inspecting a tank vehicle, what leaks should you look for around the tank body and fittings?
- ALeaks in the pipes, connections, and hoses, especially around jointsCorrect
- BOnly leaks from the fuel tank, not the cargo tank
- CLeaks are not part of a tank inspection
- DOnly leaks that appear while the vehicle is moving
Why: During the pre-trip inspection, check the tank body and shell for dents and check the pipes, connections, and hoses for leaks, paying special attention to the joints. Even a small leak can be a serious hazard, especially with hazardous cargo.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Leaks)
20. What should you check about the manhole covers and vapor vents on a tank?
- AThat they are painted the correct color
- BThat the covers have gaskets that seal properly and the vents are not cloggedCorrect
- CThat they are welded shut permanently
- DNothing; these parts are not inspected
Why: Check that manhole covers have gaskets and close (seal) properly, and that the vapor vents and pressure-relief valves work and are not clogged. Covers that do not seal can leak, and blocked vents can let dangerous pressure build up.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Manhole Covers and Vents)
21. Is it acceptable to drive a tank vehicle with an open manhole cover or an open valve?
- AYes, as long as the tank is less than half full
- BYes, if you are driving slowly
- COnly on private property
- DNo, you should never drive with open valves or manhole coversCorrect
Why: Never drive a tank vehicle with the valves open or the manhole covers open. Doing so can let liquid or vapor escape and is very dangerous. Check that intake, discharge, and cutoff valves are in the correct position before driving.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Valves and Covers)
22. Which of these is special equipment you may need to check on certain tank vehicles?
- AVapor recovery kits, grounding/bonding cables, and emergency shut-off systemsCorrect
- BA spare set of passenger seats
- CA refrigerator for the driver's food
- DExtra chrome trim on the bumper
Why: Depending on the cargo, a tank vehicle may carry special equipment such as vapor recovery kits, grounding and bonding cables, emergency shut-off systems, and built-in fire extinguishers. Check that any required equipment is present and working before the trip.
Based on: CDL Manual §8.1 — Inspecting Tank Vehicles (Special Equipment)
23. When must a tank vehicle display hazardous materials placards?
- AOnly when the tank is completely full
- BWhenever it hauls any liquid, hazardous or not
- CWhen it carries hazardous materials in amounts that require placardingCorrect
- DNever; tank vehicles do not use placards
Why: Placards are diamond-shaped warning signs that show the class of hazardous material being hauled. A tank vehicle must display the correct placards whenever it carries hazardous materials in an amount that requires placarding. This warns others of the danger.
Based on: CDL Manual §8 / §9 — Hazardous Materials (Placarding)
24. To haul a placarded amount of hazardous liquid in a cargo tank, what endorsements does a driver generally need?
- ABoth the tank (N) endorsement and the hazardous materials (H) endorsementCorrect
- BOnly a doubles/triples endorsement
- COnly a passenger endorsement
- DNo endorsement is needed for liquids
Why: Hauling hazardous materials in a tank that requires placards generally requires both the tank vehicle endorsement and the hazardous materials endorsement (often shown together as an 'X' endorsement). Each has its own knowledge test.
Based on: CDL Manual §8 — Tank Vehicles (Endorsements) / §9 Hazardous Materials
25. Why is emergency stopping harder in a partly loaded smooth bore (unbaffled) tank?
- AThe tank has too many baffles slowing the liquid
- BThe strong forward surge pushes the vehicle and can make it harder to stop under controlCorrect
- CSmooth bore tanks have no brakes
- DA partly loaded tank is always heavier than a full one
Why: In a smooth bore tank there is nothing to slow the liquid, so a partly loaded tank has a very strong forward-and-back surge. When you brake, that surge pushes the vehicle forward, which can make a controlled stop harder. Brake early and smoothly.
Based on: CDL Manual §8.2 — Driving Tank Vehicles (Liquid Surge / Unbaffled Tanks)