CDL Class A Practice Test
Class A is the license that lets you pull a proper trailer. In the federal rules it is a vehicle group rather than a test, and the definition is worth knowing before you book anything. Group A is any combination rating 26,001 pounds or more where the unit being towed rates over 10,000 pounds on its own. Both halves of that sentence matter. A heavy truck pulling a light trailer is not Class A, and neither is a light truck pulling a heavy one if the combined rating falls short.
50 questions, 40 right to pass. Free, untimed, no account.
Correct · A
At roughly what air tank pressure does the governor stop the compressor from pumping any more air?
- About 125 psi Correct answer
- About 100 psi
- About 150 psi
- About 55 psi
Texas Commercial Motor Vehicle Drivers Handbook, 5.1.2 Air Compressor Governor, p. 5-1
Class A practice test: quick facts
What this practice test does. Your state's own numbers are cited separately.
- Questions per test
- 50
- Right answers to pass
- 40
- Time limit
- None
- Cost
- FreeNo account, no card, no limit on retries
- Questions in the bank
- 428Drawn fresh every time you start
- Every answer cited
- YesDocument, section and page on each one
- Last reviewed
- September 2026Re-checked against the source once a year
- Written from
- Official state handbooks
What this test covers
Every subject below has cited questions behind it. The number is how many are in the bank right now, and each draw is weighted across them.
- Vehicle inspection 28
- Basic vehicle control 12
- Shifting gears 11
- Seeing 7
- Communicating 11
- Space management 14
- Speed management 15
- Night driving 16
- Extreme driving conditions 19
- Hazard perception 24
- Emergencies 13
- Skid control and recovery 10
- Accidents and fires 13
- Alcohol and drugs 15
- Staying alert and fit to drive 13
- Cargo 20
- Railroad crossings 12
- Rules and disqualification 11
- Getting and keeping a CDL 16
- Air brake systems 65
- Combination vehicles 83
How hard the bank is
Every test you start pulls a mix, so you get the easy marks and the ones people actually fail on.
- Straightforward 104
- Moderate 234
- Hard 90
Sample Class A questions
Real questions from the bank, with the answer and the page it came from. Open a few, then take the test properly.
At roughly what air tank pressure does the governor stop the compressor from pumping any more air?
- About 125 psi
- About 100 psi
- About 150 psi
- About 55 psi
Cut-out is around 125 psi. That is where the governor takes the compressor off load and the needle stops climbing. 100 psi is the cut-in figure, 150 psi is where the safety relief valve opens, and 55 psi is the low air warning. Confusing cut-out with cut-in is the classic mistake.
Tank pressure has been dropping as the brakes are used. At about what pressure will the governor let the compressor start pumping again?
- About 100 psi
- About 125 psi
- About 85 psi
- About 55 psi
Cut-in is around 100 psi, cut-out around 125 psi, so the system normally cycles between those two figures. 85 psi is the bottom of the pressure build-up test range and 55 psi is where the low air warning must already have come on.
An air compressor has its own oil supply rather than being lubricated by engine oil. What does that add to the driver's routine?
- Check the compressor oil level before driving
- Drain the compressor at the end of each day of driving
- Top the compressor up with alcohol in cold weather
- Nothing, because the engine oil check already covers it
A compressor with its own oil supply has to have that level checked before driving. Draining at the end of the day is the air tank routine, and the alcohol top-up belongs to the alcohol evaporator, not the compressor.
A governor is not cutting the compressor in and out at the pressures the manufacturer specifies. Why does that have to be fixed before the vehicle goes out?
- It may not keep enough air pressure in the tanks for safe driving
- It stops the brake lights from coming on when the pedal is pushed
- It disables the low air pressure warning signal
- It makes the spring brakes release on their own
The governor is what keeps a working reserve in the tanks. If it cuts in and out at the wrong pressures the reserve may never be there when it is needed. The stop light switch and the low air warning are separate devices, and nothing about a faulty governor releases spring brakes.
The air tanks on a truck have manually operated drain valves. How often does the driver have to drain them?
- At the end of each day of driving
- Once a week
- Before the start of each trip, but not afterwards
- Only when the low air pressure warning comes on
Manual drain valves are the driver's job at the end of every driving day, by a quarter turn or a pull cable, and the tank has to be drained completely. Only automatic drain valves take that job away, and even then the alcohol evaporator still needs checking in cold weather.
Why does the water that collects in the bottom of an air tank matter most in cold weather?
- It can freeze and cause the brakes to fail
- It thins the compressor oil so the compressor seizes
- It sets off the low air pressure warning while driving
- It makes the safety relief valve open below its setting
Compressed air carries water and a little compressor oil, both of which settle in the bottom of the tank. In freezing weather that water can turn to ice and take the brakes out altogether, which is why the tank is drained completely rather than just cracked open.
At about what pressure is the safety relief valve on the first air tank usually set to open?
- 150 psi
- 125 psi
- 100 psi
- 55 psi
The safety relief valve sits in the first tank the compressor pumps to and is usually set for 150 psi, well above the governor's 125 psi cut-out. If it is venting, pressure has gone somewhere it should never reach.
Air is escaping from the safety relief valve on the first air tank. What should the driver do about it?
- Treat it as a fault and have a mechanic repair it
- Nothing, since that is how the valve holds pressure steady
- Drain the tank down and carry on driving
- Reset the governor cut-out setting to a lower pressure
The safety valve is a last line of defense, not a regulator. Air coming out of it means something in the system is letting pressure rise too far, and that is a mechanic's job. Draining the tank or moving the governor setting hides the fault instead of fixing it.
How to use this test
-
Take it cold, once
Do not revise first. You want to know which subjects are actually weak, and a clean run tells you that in ten minutes.
-
Read the reason, not the score
The explanation for each answer opens on the next page with its handbook page. That is the bit that makes it stick.
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Retry only what you missed
The result page has a button for exactly that. Far faster than sitting the whole thing again.
-
Come back on another day
A different draw each time exposes different gaps. Two runs a week beats ten in one evening.
Why this one is different
You can check every answer
Document, section and page on all of them, plus the date it was read. Nothing goes live without all four.
Nothing is behind a paywall
Every question in the bank is free, every time. There is no premium tier holding the hard ones back.
Scored by subject
You find out which topic is costing you marks, not just a number out of 50.
More about this test
Three tests, not one
Because Class A is a group and not a subject, there is no single Class A exam sitting at the counter waiting for you. What there is, is a set. You take general knowledge, which every commercial driver takes whatever they drive. You take combination vehicles, which is the one that exists purely because your vehicle has a hinge in the middle. And if anything you will drive has air brakes, which in practice means almost everything in this class, you take air brakes as well.
Most practice sites make you work through those three separately and leave you to guess how they fit together. This test does not. One run pulls from all three banks at once, in the proportions you would meet them, which is a much better guide to whether you are actually ready than three separate scores that each look fine on their own.
What catches Class A drivers out
The combination material is where people lose marks, and it is rarely the theory. It is coupling order, and what the trailer does that the tractor does not. Off-tracking, where the trailer cuts the corner tighter than the cab. Rearward amplification, the reason the back of a set swings further than the front. What a converter dolly is for. Which brake you never use to straighten a jackknife.
Air brakes catches a different group. Those are number questions, and a confident guess is usually wrong. You either know at what pressure the warning comes on and at what pressure the spring brakes drop, or you do not, and no amount of general road sense will fill the gap.
How to use this
Every run draws fifty questions fresh from a bank of several hundred, so you cannot pass by memorising an order. When you finish you get a breakdown by subject rather than one number, which is the part that matters here. Scoring ninety overall while sitting at fifty on combination vehicles means you are not ready, and a single score would hide that completely. Retry only what you missed and book when every subject is strong, not just the average.
Every answer names the handbook and the page it came from, along with the month someone last checked it. If you think one is wrong you have everything you need to go and prove it.
Also worth reading
Last reviewed September 2026. Sources are re-checked against their publishers once a year.
Questions about this test
What does a Class A license actually let me drive?
Which knowledge tests do I need for Class A?
Is this the same as the real Class A test?
What happens if I skip the air brakes test?
Do I need a permit before the Class A skills test?
How many questions should I get right before booking?
Still not sure?
Every question names the document and page behind it, so a wrong answer is something you can prove rather than argue about.
Read up on this first
Drill one subject at a time
Shorter sets on a single part of this test, each with its own explanation and the same cited answers. Useful when one subject is costing you the pass.
- Compressor and governor 4 questions
- Chambers, slack adjusters and drums 4 questions
- Air brake inspection and leak tests 4 questions
- Brake lag and stopping distance 4 questions
- Dual air systems 4 questions
- Using air brakes on the road 5 questions
- Spring and parking brakes 5 questions
- Tanks, valves and lines 4 questions
Other tests to take
- Class B 50 questions, 40 to pass
- Class C 50 questions, 40 to pass
- General Knowledge 50 questions, 40 to pass
- Air Brakes 25 questions, 20 to pass
- Combination Vehicles 20 questions, 16 to pass
- Hazmat 30 questions, 24 to pass
- Tanker 20 questions, 16 to pass
- Doubles/Triples 20 questions, 16 to pass
- Passenger 20 questions, 16 to pass
- School Bus 20 questions, 16 to pass
- Pre-Trip 30 questions
Ready when you are.
50 questions drawn fresh from 428 cited ones. No account, nothing to pay, and every question in the bank is free.