VA · L (restriction removed) Endorsement

Virginia Air Brakes CDL Practice Test

Below are 25 exam-style questions for the Virginia Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Virginia Department of Motor Vehicles. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.

Question 1 of 25

Air pressure builds back up by:

A The brake pedal
B The compressor pumping air back into the storage tanks
C The driver inflating the tank with a portable pump
D The vehicle's motion

Correct answer: B

The engine-driven compressor refills the tanks; the brake pedal only controls release of stored air.

Question 2 of 25

You should NOT drain the wet tank when:

A There is no situation in which draining is wrong
B The vehicle is in motion
C You are about to begin a trip
D It is full of moisture

Correct answer: A

Daily draining is a routine task; there is no situation where draining is unsafe (other than while driving).

Question 3 of 25

Spring brakes do NOT replace:

A The horn
B The headlights
C The tail lights
D The service brakes for normal stops

Correct answer: D

Spring brakes are for parking and emergency only — never for normal service braking.

Question 4 of 25

Air pressure should normally build from 50 to 90 psi within:

A It does not matter
B About 3 minutes in dual systems
C Less than 30 seconds
D 10 minutes

Correct answer: B

Dual air systems should build from 50 to 90 psi within about 3 minutes at idle.

Question 5 of 25

The air compressor governor controls:

A Brake pad wear
B Coolant temperature
C Engine RPM
D When the air compressor will pump air into the storage tanks

Correct answer: D

The governor cuts the compressor in (start pumping) at low pressure and cuts it out (stop pumping) at high pressure to maintain a working range.

Question 6 of 25

You should test the trailer service brakes by:

A Listening for a hiss
B Pumping them while parked
C Releasing the parking brakes, moving the vehicle slowly forward, and applying the trailer hand valve
D Looking at the gauge

Correct answer: C

A low-speed pull-and-stop with the trailer hand valve confirms the trailer brakes apply on their own.

Question 7 of 25

Front-wheel brakes are required on commercial vehicles because:

A They look balanced
B They reduce stopping distance significantly without normally causing skids on dry pavement
C They make steering easier
D Federal law mandates them as decorative

Correct answer: B

Front brakes provide a large share of stopping force and modern vehicles are designed so they do not cause front-wheel skids on dry pavement.

Question 8 of 25

Brake-lag distance for a CMV traveling 55 mph is approximately:

A 300 feet
B 0 feet
C 142 feet
D 32 feet

Correct answer: D

About 32 feet at 55 mph for the brake lag alone — added to reaction and braking distances.

Question 9 of 25

A common practice during a long brake-recharge wait is to:

A Drain the wet tank
B Disable the warning lamp
C Check the brake light visibility
D Allow the system to reach operating pressure before driving

Correct answer: D

Always wait for full operating pressure (typically around 120 psi) before moving the vehicle.

Question 10 of 25

When applying the foot brake hard:

A Air pressure may drop slightly
B Air pressure should remain unchanged
C The compressor cuts out
D Air pressure increases

Correct answer: A

A small drop is expected during heavy application. The compressor recharges the system back up to cut-out pressure.

Question 11 of 25

Each axle group on an air-brake-equipped vehicle has its own:

A Air compressor
B Engine
C Set of brake chambers
D Drive shaft

Correct answer: C

Each axle group has its own brake chambers fed by the air system; one compressor supplies all of them.

Question 12 of 25

When testing low-air warning, you should:

A Disconnect the trailer
B Pump the brake to fan down the pressure and verify the warning activates before pressure drops below 60 psi
C Drain the wet tank only
D Look at the dashboard light

Correct answer: B

Fan the brakes (engine off) until the warning device activates and confirm it is above 60 psi.

Question 13 of 25

When the parking brake is set, the dashboard valve will normally:

A Stay pushed in
B Stay popped out and yellow
C Have no indication
D Flash red

Correct answer: B

Yellow diamond-shaped valves stay out (popped) when parking brakes are applied; pushing them in releases the brakes.

Question 14 of 25

When you press the brake pedal, brake pressure is:

A Built up from zero by the pedal
B Created by the pedal mechanically
C Received from a separate accumulator
D Released from the storage tanks

Correct answer: D

Pressing the pedal releases stored air from the tanks into the brake chambers; the pedal does not generate pressure itself.

Question 15 of 25

A leaking air system on a parked truck is dangerous because:

A When pressure drops far enough, spring brakes apply suddenly and the vehicle becomes unmovable
B The engine will not start
C It can wake the driver
D The fuel will leak

Correct answer: A

A bigger problem is en route: if a slow leak goes unnoticed and pressure drops below the spring-brake set point, the brakes apply on the road.

Question 16 of 25

A brake check ahead of a downgrade should be done:

A At the bottom only
B In the middle of the descent
C Once a year
D Before reaching the top, while still on level ground

Correct answer: D

A brief brake test on level ground at the top reveals problems while you can still stop safely.

Question 17 of 25

When approaching a long downgrade, you should:

A Skip the brake test
B Coast in neutral
C Test the brakes at the bottom
D Test the brakes by lightly applying them at the top

Correct answer: D

A light brake application at the top tests for pulling or weakness before the descent puts heat into the system.

Question 18 of 25

On a vehicle with dual air brakes, the warning device must come on before pressure in either system drops below:

A 20 psi
B Never; only the gauge needs to read it
C 60 psi
D 40 psi

Correct answer: C

The low-air warning must activate before pressure drops below 60 psi in either circuit.

Question 19 of 25

Glad-hand seals should be:

A Free of dirt and damage and properly seated
B Coated with oil
C Removed for inspection
D Loose for easy connection

Correct answer: A

Damaged or dirty seals cause leaks. Inspect and clean them as part of the trailer hookup.

Question 20 of 25

When applying brakes in an emergency without ABS:

A Press as hard as possible and hold
B Use stab braking — apply hard, release when wheels lock, re-apply
C Use only the parking brake
D Pump rapidly and lightly

Correct answer: B

Stab braking keeps the truck straight in an emergency without ABS. Hard continuous pressure can lock the wheels and cause a jackknife.

Question 21 of 25

Slack adjusters should be checked because:

A They control trailer height
B They are decorative
C Out-of-adjustment slack adjusters can result in brakes that do not work properly
D They affect engine performance

Correct answer: C

Slack adjusters convert pushrod motion into braking force. Out-of-adjustment slack adjusters reduce braking ability and are a common out-of-service item.

Question 22 of 25

Why should you NOT use the trailer hand valve to hold a parked combination vehicle?

A It only works while the engine is running
B It will activate the spring brakes
C Air leaks could cause the brakes to release and let the vehicle roll
D It is illegal

Correct answer: C

The hand valve relies on continuous air pressure. A slow leak releases the brakes and the vehicle rolls.

Question 23 of 25

During the seven-step air-brake check, the final step is to:

A Check tire pressures
B Drain the wet tank
C Pull forward and apply the foot brake to test for stopping
D Adjust the slack adjusters

Correct answer: C

After all stationary tests, perform a moving brake check at low speed to verify the service brakes stop the vehicle.

Question 24 of 25

The proper braking technique on a long downgrade is:

A Apply the parking brake
B Heavy continuous braking
C Coast in neutral
D Light, intermittent braking with engine braking and a low gear

Correct answer: D

Use the proper low gear so engine braking does most of the work; brief, moderate brake applications keep the speed in check.

Question 25 of 25

Anti-lock braking systems (ABS) on air-brake vehicles:

A Replace foundation brakes
B Are required only on hazmat trailers
C Help prevent wheel lockup but do not necessarily shorten stopping distance
D Are optional and rarely installed

Correct answer: C

ABS helps the driver maintain steering control by preventing wheel lockup. It does not necessarily reduce stopping distance.

Study tips for the Virginia Air Brakes exam

The Air Brakes portion of the Virginia CDL exam is graded out of the bank of questions the Virginia Department of Motor Vehicles draws from each year. While the exact bank is not published, every question is sourced from the Air Brakes chapter of the Virginia CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Virginia handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Air Brakes.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Virginia Department of Motor Vehicles will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Air Brakes exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Virginia General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the Air Brakes study guide and the matching chapter in the official Virginia CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Virginia Department of Motor Vehicles office.

Already comfortable with this endorsement? Drill another: VA General Knowledge · VA Combination Vehicles · VA Hazardous Materials · VA Passenger · VA School Bus · VA Tank Vehicle · VA Doubles / Triples

New to the CDL process in Virginia? Read How to apply for a CDL in Virginia for the document checklist and step-by-step timeline.