Washington Tanker CDL Practice Test

This is a free 20-question practice test for the Tanker portion of the Washington Commercial Driver's License knowledge exam. Questions are pulled from a pool of 50 drawn from the AAMVA CDL Manual, which is the source document the Washington State Department of Licensing uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in Washington.

Question 1 of 20

A "baffled" tank has:

Walls with holes that slow surge but allow flow
No walls
Only one compartment
Outside reinforcement

Correct. Baffled tanks have internal bulkheads with holes — they slow surge but still allow product to flow through during loading and unloading.

Question 2 of 20

A "tank vehicle" requiring an N endorsement is generally defined as:

Any commercial vehicle
A vehicle used to transport liquid or gaseous materials in a tank with rated capacity of 1,000 gallons or more, individual tanks of 119+ gallons
Only fuel trucks
Only vehicles over 80,000 lbs

Correct. The N endorsement is required for any commercial vehicle hauling liquid or gas in a permanently mounted tank or portable tank with rated capacity of 1,000+ gallons (and individual tanks of 119+ gallons).

Question 3 of 20

Tankers have a high center of gravity because:

The driver sits high
The load is in a tall, narrow tank
The cargo is light
The cab is wide

Correct. A tank carries its load high above the road. The center of gravity is much higher than for a flatbed of the same weight, increasing rollover risk.

Question 4 of 20

Tank vehicles should not be driven:

On long downgrades without a lower gear and intermittent firm braking
On any highway
Anywhere
At night

Correct. On long downgrades, select a low gear before starting down and use firm intermittent brake applications to prevent fade.

Question 5 of 20

When you drive a tanker on slippery roads, you should:

Drive faster
Reduce speed substantially and increase following distance
Use only the trailer brake
Maintain normal speed

Correct. Reduce speed by at least one-third on wet roads, by half on snow. Liquid loads make recovery from a skid much harder.

Question 6 of 20

Cargo tanks must be inspected and tested:

Periodically per CFR requirements; intervals depend on tank specification (MC-306, MC-307, MC-312, DOT-406, etc.)
Once a decade
Never
Only when leaks appear

Correct. Cargo tanks have specific inspection and test schedules based on their DOT specification (visual, leakage, internal, pressure, and thickness tests).

Question 7 of 20

Side-to-side surge is most likely to cause:

Improved fuel economy
Rollover, especially on curves and in evasive maneuvers
No effect
Better braking

Correct. Side-to-side surge can amplify side-loading forces, contributing to rollover on curves and exit ramps.

Question 8 of 20

When braking a partially filled smooth-bore tank, you should:

Brake hard at the last minute
Brake gently and start braking earlier than usual to compensate for surge
Use only the trailer hand valve
Pump the brakes

Correct. In smooth-bore tanks, surge is severe. Brake gently and earlier than you would in a dry-van trailer to avoid being pushed forward.

Question 9 of 20

When you discover a leak in a cargo tank carrying flammable liquid:

Continue to the destination
Stop in a safe location, secure the area, contact emergency response and the carrier — never transfer cargo on the road
Try to drive around the leak
Pour water on it

Correct. A leaking flammable cargo tank is a major incident — secure the area, evacuate per the ERG, contact emergency services. Never attempt roadside cargo transfer.

Question 10 of 20

Outage refers to:

Empty space left at the top of a tank to allow liquid expansion
The brake-out system
A power failure
A driver shortage

Correct. Outage is the empty space left at the top of a tank to allow liquid to expand as it warms. Different liquids require different outage percentages.

Question 11 of 20

Empty tankers handle:

The same as loaded tankers
Differently — lighter axle weight reduces braking traction; tankers are also more affected by crosswinds when empty
Always better
Always worse

Correct. Empty tankers have less brake traction (less weight on tires) and are more affected by crosswinds. Never assume empty equals safer.

Question 12 of 20

A pressure-relief device that vents during transit:

Is a normal occurrence
Is a serious malfunction or over-fill — stop and investigate
Means the tank is empty
Means the load is cold

Correct. Continuous venting indicates over-pressure (often from over-fill or sun heating an over-filled tank). Stop and investigate; do not continue with a venting tank.

Question 13 of 20

When the surge in a tanker pushes the rig forward at a stop, you may:

Brake harder
Be pushed past the intended stopping point
Skid backward
Have no effect

Correct. Forward surge can push the entire rig forward — past stop lines, into intersections, into the vehicle ahead. Plan your stops with extra distance.

Question 14 of 20

A tanker with a high center of gravity is most prone to rollover during:

Straight-line driving
Tight curves, evasive maneuvers, and exit ramps
Backing
Stopping

Correct. High center of gravity makes tankers roll on tight curves, sudden lane changes, and exit ramps. Slow well in advance.

Question 15 of 20

When emergency-braking a smooth-bore tanker:

Brake hard
Anticipate forward surge that can throw your weight against the wheel and may push the rig past your intended stopping distance
Use only trailer brake
No special concern

Correct. Forward surge can dramatically push a smooth-bore tank rig further than expected. Plan stopping distance with significant additional margin.

Question 16 of 20

Pressure relief devices on cargo tanks are designed to:

Open if pressure inside exceeds safe limits, releasing product or vapor before the tank ruptures
Increase pressure
Be tightened down
Stay closed at all times

Correct. Pressure relief valves open at a set pressure to prevent tank rupture. Tampering with them is illegal and dangerous.

Question 17 of 20

A double trailer tanker requires:

Both N (Tanker) and T (Doubles/Triples) endorsements, plus possibly H (Hazmat)
Only the N endorsement
No endorsements
Only the H endorsement

Correct. Pulling more than one tank requires Doubles/Triples (T) plus Tanker (N) endorsements. Add Hazmat (H) — together written X — for hazardous liquid loads.

Question 18 of 20

When you stop a placarded tanker carrying flammable liquid at a railroad crossing, you must stop:

On the rails
Between 15 and 50 feet from the nearest rail, then proceed only when safe
Anywhere
Only if a train is in sight

Correct. Placarded hazmat (which most fuel tankers are) must stop 15 to 50 feet from the nearest rail. Look, listen, and cross only when clear.

Question 19 of 20

Carrying a smooth-bore tank up a ramp or off a curb:

Causes minimal surge
Can produce strong front-to-back surge that affects throttle and traction
Has no effect
Improves traction

Correct. Climbing causes the load to surge backward and then forward as you level off — affecting throttle response, traction, and braking.

Question 20 of 20

Tank specification "MC-306" or "DOT-406" generally refers to:

Cargo tanks designed for non-pressure flammable and combustible liquids (e.g., gasoline, diesel)
High-pressure gases
Cryogenic liquids
Hazardous solids

Correct. MC-306 (older) and DOT-406 (current) are non-pressure cargo tanks for flammable and combustible liquids — typical fuel tankers.

About the Washington Tanker exam

Most states administer 20 Tanker questions and require 80% to pass. Topics include the unique handling of liquid loads, surge effects, baffles vs. smooth-bore, outage and expansion, inspection of the cargo tank, and emergency procedures.

The Washington State Department of Licensing follows the federal CDL standards established by FMCSA. To earn the Tanker credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full Tanker question bank or browse all Washington CDL practice tests.