Free CDL Practice Tests · All 50 States + DC · Updated 2026 Official handbooks · CDL pay & outlook
NV · L (restriction removed) Endorsement

Nevada Air Brakes CDL Practice Test

Below are 25 exam-style questions for the Nevada Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Nevada 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
The total stopping distance for an air-brake equipped vehicle is:
  • A Perception + reaction + brake-lag + braking distance
  • B Reaction + braking + brake-lag distance
  • C Perception + braking distance
  • D Reaction distance + braking distance
Correct answer: A
Air brakes add a brake-lag distance — the time from foot-pressure to actual brake application — that hydraulic systems do not have.
Question 2 of 25
After making the initial brake application, the air-pressure drop should not exceed:
  • A 2-3 psi
  • B 1 psi
  • C 5 psi
  • D 10 psi
Correct answer: A
A small initial drop is normal as the system equalizes — but excessive drop indicates a leak.
Question 3 of 25
Which is the proper procedure when the low-air warning comes on while driving?
  • A Increase engine RPM
  • B Continue to the next exit
  • C Pump the brakes to keep pressure
  • D Bring the vehicle to a safe stop as soon as possible and find the cause
Correct answer: D
Continued driving below safe air pressure risks losing service brakes entirely. Stop safely and diagnose.
Question 4 of 25
If air pressure drops in the emergency line:
  • A Tractor brakes apply
  • B Trailer spring brakes apply automatically
  • C Nothing happens
  • D Trailer service brakes apply
Correct answer: B
Loss of supply-line pressure is the failsafe that triggers the trailer's spring brakes.
Question 5 of 25
The air compressor governor controls:
  • A When the air compressor will pump air into the storage tanks
  • B Engine RPM
  • C Brake pad wear
  • D Coolant temperature
Correct answer: A
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
After parking a tractor-trailer:
  • A Set only the trailer parking brake
  • B Leave both released
  • C Set both tractor and trailer parking brakes
  • D Set only the tractor parking brake
Correct answer: C
Federal practice is to set both parking brakes when fully parked. The exception is during coupling/uncoupling, where the trailer brakes are set.
Question 7 of 25
When doing the air-leak rate test, the engine should be:
  • A Running at high RPM
  • B Started and stopped repeatedly
  • C Off, with brakes released for the first part
  • D In gear
Correct answer: C
Engine off, brakes released to test static leak rate; then brakes applied and held for the second part.
Question 8 of 25
You should not over-tighten a glad-hand because:
  • A It violates federal weight law
  • B It is bad luck
  • C It will reduce engine power
  • D It can damage the rubber seals
Correct answer: D
Over-tightening crushes the seals. The connection should be firm but not forced.
Question 9 of 25
Spring brakes do NOT replace:
  • A The headlights
  • B The tail lights
  • C The horn
  • D The service brakes for normal stops
Correct answer: D
Spring brakes are for parking and emergency only — never for normal service braking.
Question 10 of 25
Why should you NOT use the trailer hand valve to hold a parked combination vehicle?
  • A It will activate the spring brakes
  • B Air leaks could cause the brakes to release and let the vehicle roll
  • C It only works while the engine is running
  • D It is illegal
Correct answer: B
The hand valve relies on continuous air pressure. A slow leak releases the brakes and the vehicle rolls.
Question 11 of 25
The air compressor is driven by:
  • A The transmission
  • B The engine, by belts or directly geared
  • C The electrical system
  • D The exhaust system
Correct answer: B
Compressors are typically engine-driven, either by a belt or direct gearing, so air pressure builds whenever the engine runs.
Question 12 of 25
When testing low-air warning, you should:
  • A Drain the wet tank only
  • B Look at the dashboard light
  • C Disconnect the trailer
  • D Pump the brake to fan down the pressure and verify the warning activates before pressure drops below 60 psi
Correct answer: D
Fan the brakes (engine off) until the warning device activates and confirm it is above 60 psi.
Question 13 of 25
Cross-leakage between primary and secondary brake systems is:
  • A Caused by overuse
  • B A normal feature
  • C Required by federal law
  • D A serious defect that can prevent backup braking
Correct answer: D
Each circuit must remain independent so a failure in one still leaves the other working.
Question 14 of 25
When applying brakes in an emergency with ABS:
  • A Pump rapidly
  • B Stab the brakes
  • C Press as hard as possible and hold
  • D Release the brakes immediately
Correct answer: C
With ABS, full pressure works because the system pulses for you, allowing maximum braking while preserving steering.
Question 15 of 25
Air pressure should normally build from 50 to 90 psi within:
  • A 10 minutes
  • B About 3 minutes in dual systems
  • C Less than 30 seconds
  • D It does not matter
Correct answer: B
Dual air systems should build from 50 to 90 psi within about 3 minutes at idle.
Question 16 of 25
A foot-valve pressure gauge reading lower than expected during a brake application could indicate:
  • A A leak or restriction
  • B Normal operation
  • C A worn seat belt
  • D A new compressor
Correct answer: A
Low pressure during application means the system isn't delivering full braking force — investigate.
Question 17 of 25
Modulating valves on the rear axle help prevent:
  • A Wheel lockup during emergency braking
  • B Engine overheating
  • C Tire blowouts
  • D Steering wander
Correct answer: A
Modulating valves and ABS sensors release pressure briefly to keep wheels from locking.
Question 18 of 25
When the air pressure in the brake system drops too low:
  • A The trailer hand valve releases
  • B The engine stops
  • C Nothing happens until you stop
  • D Spring brakes apply automatically
Correct answer: D
When system pressure drops, typically below 20-45 psi, mechanical springs apply the brakes regardless of driver input.
Question 19 of 25
During the seven-step air-brake check, the final step is to:
  • A Check tire pressures
  • B Adjust the slack adjusters
  • C Drain the wet tank
  • D Pull forward and apply the foot brake to test for stopping
Correct answer: D
After all stationary tests, perform a moving brake check at low speed to verify the service brakes stop the vehicle.
Question 20 of 25
After releasing the parking brake on a tractor, you should:
  • A Pump the service brake five times
  • B Drive immediately
  • C Wait for full system pressure before moving
  • D Drain the wet tank
Correct answer: C
Make sure the system reaches at least the cut-out pressure (typically around 120 psi) before driving.
Question 21 of 25
Air pressure builds back up by:
  • A The driver inflating the tank with a portable pump
  • B The compressor pumping air back into the storage tanks
  • C The vehicle's motion
  • D The brake pedal
Correct answer: B
The engine-driven compressor refills the tanks; the brake pedal only controls release of stored air.
Question 22 of 25
Spring brakes are held off by:
  • A Electrical current
  • B Engine vacuum
  • C Hydraulic pressure
  • D Air pressure
Correct answer: D
Compressed air holds the springs back. When air pressure drops, the springs apply the brakes mechanically.
Question 23 of 25
When applying the foot brake hard:
  • A Air pressure should remain unchanged
  • B Air pressure may drop slightly
  • C Air pressure increases
  • D The compressor cuts out
Correct answer: B
A small drop is expected during heavy application. The compressor recharges the system back up to cut-out pressure.
Question 24 of 25
Brake drums in good condition will:
  • A Be coated with oil
  • B Have small cracks
  • C Be glowing red after stops
  • D Be free of cracks longer than half the width of the friction area
Correct answer: D
Cracks longer than half the friction area or any visible heat checks usually fail inspection.
Question 25 of 25
When approaching a long downgrade, you should:
  • A Test the brakes by lightly applying them at the top
  • B Skip the brake test
  • C Coast in neutral
  • D Test the brakes at the bottom
Correct answer: A
A light brake application at the top tests for pulling or weakness before the descent puts heat into the system.

Study tips for the Nevada Air Brakes exam

The Air Brakes portion of the Nevada CDL exam is graded out of the bank of questions the Nevada 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 Nevada 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 Nevada 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 Nevada 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 Nevada 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 Nevada 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 Nevada Department of Motor Vehicles office.

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

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