Which CDL tests do I have to pass?

For a Class A licence: General Knowledge, plus Air Brakes and Combination Vehicles if your vehicle has them — which for a tractor-trailer it does. Endorsements such as Hazmat or Tanker are separate tests.

How many questions are on the CDL General Knowledge test?

50 in most states, and 80% correct to pass. Air Brakes is typically 25 questions and Combination Vehicles 20.

Why do these questions only have three options?

Because the real CDL test does. Most states use three options rather than four, so practising with four would train the wrong reflex.

Is this CDL practice test free?

Yes — every question here is free, with no account and no email.

Why does an air-braked vehicle have a delay between pressing the brake pedal and the brakes actually working, a delay that a car with hydraulic brakes does not have?

The compressed air needs time to travel down the lines and reach the brake chambers

The air compressor must first pump the tanks back up to governor cut-out pressure

The spring brakes must fully release before the service brakes can be applied

An exit ramp posted at 35 mph curves and runs downhill at the same time. You are loaded near your gross weight. What is the correct approach?

Get your speed well down before you reach the curved part, because the posted speed is aimed at cars and braking while turning on a downgrade is a bad combination

Enter at the posted 35 mph, since posted ramp speeds are set for the heaviest legal vehicle

Carry your highway speed onto the ramp and brake steadily through the curve to stay smooth

A load is right at the state's legal maximum weight, and the route ahead crosses a snowy mountain pass. What does the driver's responsibility require here?

Recognizing that the legal maximum may not be a safe weight in those conditions and taking that into account before starting

Nothing further, because a load at the legal maximum is by definition safe on any road

Letting air out of the tires so they grip the snow better on the grades

During the final air brake check you keep stepping on and off the pedal to bleed pressure down past the low pressure warning. What should the vehicle do on its own?

Pop the parking brake valve out, along with the tractor protection valve on a tractor-trailer, setting the spring brakes

Hold the service brakes on by itself and keep them applied until air is restored

Start the compressor without the engine running and begin recharging the tanks

You are running empty on a windy day and are about to exit a long tunnel. What should you expect?

A sudden sideways push as you leave the tunnel, since a light vehicle is moved more easily by wind

Steadier steering, because the tunnel walls have already stabilized the trailer

No noticeable effect, since wind only affects loaded trailers with high centers of gravity

You are about to drive straight across a two-lane road from a side road. What must you confirm before you start moving?

That the whole vehicle can clear both lanes before oncoming traffic arrives

That the near lane is clear, since you can pause in the middle if the far lane fills

That approaching drivers have seen you and are slowing

Before raising the hood or tilting the cab to inspect the engine compartment, what must be confirmed?

That the parking brakes are applied, the wheels chocked, or both.

That the engine is running, so you can hear the belts and accessories at work.

That the engine has cooled enough for the radiator cap to be removed safely.

You have to drive well below the speed of surrounding traffic for several miles. What is true about using the four-way flashers?

In states whose law permits them in motion, they are a good way to alert drivers closing on you

They are for night-time use only; in daylight a large vehicle is warning enough on its own

They may only be used when the vehicle is completely stopped, in every state

Why must the trailer hand valve never be used to hold a parked trailer in place?

Air pressure alone is holding those brakes, and once it bleeds down a trailer with no spring brakes has nothing left

It applies only the tractor's brakes, so the trailer is free to roll anyway

It empties the trailer tanks each time it is released

What is the purpose of the driver's vehicle inspection report completed after a trip?

It puts the faults the driver found in front of the people who repair the vehicle.

It records the driver's on-duty hours for the log audit.

It releases the driver from responsibility for any defect later found on that vehicle.

Free CDL Practice Test 2026

The three written tests a Class A driver has to pass — General Knowledge, Air Brakes and Combination Vehicles — in the real three-option format, with every answer explained. Written from the AAMVA model manual and state CDL handbooks.

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The three knowledge tests

Try 10 questions now

Tap an option to see the answer and the reasoning behind it.

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1.
Why does an air-braked vehicle have a delay between pressing the brake pedal and the brakes actually working, a delay that a car with hydraulic brakes does not have?
Not quiteCorrect answer: A — The compressed air needs time to travel down the lines and reach the brake chambers
Hydraulic fluid is nearly incompressible, so a car's brakes bite as soon as the pedal moves. Air is compressible and has to flow through long lines before it can push the chamber pushrods, and that transit time is why roughly half a second or more passes before braking force appears.
Believing brake lag is caused by the compressor or by low tank pressure, so a driver assumes a full, healthy air system means there is no lag at all.
2.
An exit ramp posted at 35 mph curves and runs downhill at the same time. You are loaded near your gross weight. What is the correct approach?
Not quiteCorrect answer: B — Get your speed well down before you reach the curved part, because the posted speed is aimed at cars and braking while turning on a downgrade is a bad combination
Ramp speeds are set for passenger cars, and a loaded high-center-of-gravity vehicle has far less margin. A downgrade fights your braking while the curve is already using up your available traction, so the speed must come off before the geometry starts.
Reading a posted ramp speed as a guarantee for any vehicle. Ramp rollovers are a signature commercial-vehicle crash precisely because drivers treat the sign as validated for their load.
3.
A load is right at the state's legal maximum weight, and the route ahead crosses a snowy mountain pass. What does the driver's responsibility require here?
Not quiteCorrect answer: A — Recognizing that the legal maximum may not be a safe weight in those conditions and taking that into account before starting
Legal limits are written for ordinary roads and ordinary weather. Grades and slick surfaces change stopping and control long before any regulation changes, so the judgment has to be made by the driver, before the wheels turn.
Equating legal with safe, so a clean scale ticket is treated as settling the question regardless of terrain or weather.
4.
During the final air brake check you keep stepping on and off the pedal to bleed pressure down past the low pressure warning. What should the vehicle do on its own?
Not quiteCorrect answer: C — Pop the parking brake valve out, along with the tractor protection valve on a tractor-trailer, setting the spring brakes
Once pressure is too low to hold the spring brakes released, those valves close on their own and the knobs come out, setting the parking brakes. Watching this happen at the pressure the manufacturer specifies proves the vehicle will stop itself rather than roll on with no braking if the air supply is lost.
Assuming an air loss simply leaves you with no brakes, missing that spring brakes are designed to apply automatically, and that this behavior is testable before the trip.
5.
You are running empty on a windy day and are about to exit a long tunnel. What should you expect?
Not quiteCorrect answer: B — A sudden sideways push as you leave the tunnel, since a light vehicle is moved more easily by wind
Tunnel walls shield the vehicle from crosswind, so the full force arrives all at once at the exit, and an empty trailer has the least weight resisting it.
The belief that a heavier load makes a vehicle more vulnerable to wind, when in fact the lighter the vehicle the more easily wind pushes it out of its lane.
6.
You are about to drive straight across a two-lane road from a side road. What must you confirm before you start moving?
Not quiteCorrect answer: A — That the whole vehicle can clear both lanes before oncoming traffic arrives
A long vehicle cannot stop partway across without blocking a lane, and there is no safe refuge in the middle of the road, so the whole crossing has to be committed to in advance.
The belief that a crossing can be made in two stages the way a car might, ignoring that a combination vehicle is too long to wait anywhere in the middle.
7.
Before raising the hood or tilting the cab to inspect the engine compartment, what must be confirmed?
Not quiteCorrect answer: A — That the parking brakes are applied, the wheels chocked, or both.
You are about to stand in front of a loaded vehicle with your hands inside it. Securing it against rolling protects the inspector, which is why this comes before anything is opened.
Thinking of the parking brake and chocks as yard equipment for parked trailers, rather than personal protection for whoever is standing ahead of the front wheels.
8.
You have to drive well below the speed of surrounding traffic for several miles. What is true about using the four-way flashers?
Not quiteCorrect answer: B — In states whose law permits them in motion, they are a good way to alert drivers closing on you
Traffic coming up behind badly misjudges the rate at which it is gaining on a slow vehicle, and flashers are what breaks that misjudgement in time. The catch is that permission to run them while moving is set state by state, so this is one point where you have to know the law where you are driving rather than one national answer.
Assuming flasher rules are uniform across the country. A driver who applies their home state's rule everywhere is either forgoing a useful warning or using a signal illegally, depending on which way they guessed.
9.
Why must the trailer hand valve never be used to hold a parked trailer in place?
Not quiteCorrect answer: C — Air pressure alone is holding those brakes, and once it bleeds down a trailer with no spring brakes has nothing left
The hand valve holds the trailer brakes with air pressure alone, and air left standing will eventually bleed off. Parking brakes hold mechanically with springs, and where a trailer has none, wheel chocks are what keep it from rolling.
Treating any brake that feels firm right now as a parking brake. Air-applied brakes hold only while the air lasts; parking brakes hold when the air is gone.
10.
What is the purpose of the driver's vehicle inspection report completed after a trip?
Not quiteCorrect answer: A — It puts the faults the driver found in front of the people who repair the vehicle.
The report is the mechanism by which what the driver noticed becomes work the shop actually performs. It is a repair order written by the person who was closest to the failure.
Treating the report as the driver's personal liability shield rather than the carrier's repair order, which leads to vague entries that no mechanic can act on.

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Questions people ask

Which CDL tests do I have to pass?: For a Class A licence: General Knowledge, plus Air Brakes and Combination Vehicles if your vehicle has them — which for a tractor-trailer it does. Endorsements such as Hazmat or Tanker are separate tests.
How many questions are on the CDL General Knowledge test?: 50 in most states, and 80% correct to pass. Air Brakes is typically 25 questions and Combination Vehicles 20.
Why do these questions only have three options?: Because the real CDL test does. Most states use three options rather than four, so practising with four would train the wrong reflex.
Is this CDL practice test free?: Yes — every question here is free, with no account and no email.

Where this comes from

49 CFR Part 383 — Commercial Driver's License Standards; Requirements and Penalties — U.S. Federal Motor Carrier Safety Administration
49 CFR Part 392 — Driving of Commercial Motor Vehicles — U.S. Federal Motor Carrier Safety Administration
49 CFR Part 393 — Parts and Accessories Necessary for Safe Operation — U.S. Federal Motor Carrier Safety Administration
49 CFR Part 395 — Hours of Service of Drivers — U.S. Federal Motor Carrier Safety Administration
49 CFR Part 396 — Inspection, Repair, and Maintenance — U.S. Federal Motor Carrier Safety Administration
Commercial Driver's License Manual (AAMVA Modernized Testing System), 2026 edition published by the Virginia DMV — American Association of Motor Vehicle Administrators / Virginia DMV
New York State Commercial Driver's Manual — English (CDL-10) and official Spanish edition (CDL-10S) — New York State DMV
Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition — U.S. Federal Highway Administration

Independent study aid. Not affiliated with, endorsed by or connected to any Department of Motor Vehicles or government agency. Questions are written from the official handbooks listed above; no exam result is guaranteed.