CDL General Knowledge Practice Test
The general knowledge test is the one every commercial driver sits, whatever class of licence you are after and whichever endorsements you plan to add later. It is the only CDL knowledge test that nobody can skip. Get it out of the way properly and the rest of the process gets a lot easier.
50 questions, 40 right to pass. Free, untimed, no account.
Correct · A
A driver is behind a 60-foot rig at 35 mph. Using the one-second-per-ten-feet rule, how many seconds of following distance should they keep?
- 6 seconds Correct answer
- 4 seconds
- 5 seconds
- 7 seconds
Texas Commercial Motor Vehicle Drivers Handbook, 2.7.1 – Space Ahead, p. 2-16
General Knowledge 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
- 280Drawn 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
- Texas Commercial Motor Vehicle Drivers Handbook
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
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 76
- Moderate 148
- Hard 56
Sample General Knowledge questions
Real questions from the bank, with the answer and the page it came from. Open a few, then take the test properly.
A driver is behind a 60-foot rig at 35 mph. Using the one-second-per-ten-feet rule, how many seconds of following distance should they keep?
- 6 seconds
- 4 seconds
- 5 seconds
- 7 seconds
Below 40 mph the rule is one second of following distance for every ten feet of vehicle length, with no extra added. A 60-foot vehicle is six ten-foot units, so six seconds is the minimum gap at this speed.
A driver of a 40-foot combination vehicle is traveling at 45 mph. How many seconds of following distance should they keep?
- 5 seconds
- 4 seconds
- 6 seconds
- 3 seconds
A 40-foot vehicle needs four seconds under the one-second-per-ten-feet rule, but the handbook adds one more second whenever speed is above 40 mph. That makes five seconds the right gap here.
To check your following distance, from what point should you start counting seconds?
- The moment the vehicle ahead passes a fixed point on the road
- The moment you first spot the vehicle ahead in the distance
- The moment you take your foot off the accelerator
- Only once your speed passes 40 mph
Pick a landmark, such as a shadow or a pavement marking, and start counting "one thousand-and-one, one thousand-and-two" the instant the vehicle ahead passes it. Comparing your count to the same landmark shows whether you're keeping enough space.
Total stopping distance is the sum of which three distances?
- Perception distance, reaction distance, and braking distance
- Following distance, braking distance, and coasting distance
- Reaction distance, coupling distance, and braking distance
- Perception distance, signaling distance, and coasting distance
Perception distance is how far you travel before your brain registers a hazard, reaction distance is how far you travel before your foot hits the brake, and braking distance is how far the vehicle travels while braking. Add all three for total stopping distance.
At 55 mph, on dry pavement with good brakes, total stopping distance is closest to which distance?
- About 419 feet
- About 216 feet
- About 142 feet
- About 61 feet
The handbook adds perception distance (about 142 feet at 55 mph), reaction distance (about 61 feet) and braking distance (about 216 feet) to reach a total minimum stopping distance of about 419 feet at that speed.
If a vehicle's speed increases from 20 mph to 60 mph, how much greater do impact and braking distance become?
- About 9 times greater
- About 3 times greater
- About 4 times greater
- About 16 times greater
Tripling speed from 20 to 60 mph makes impact and braking distance about nine times greater, not three times. Doubling speed from 20 to 40 mph only gets you to four times greater, which is why high speed is far more dangerous than it feels.
About how much should a driver reduce speed on a wet road compared to a dry one?
- About one-third, for example from 55 to about 35 mph
- No reduction is needed if the vehicle has good tires
- About one-tenth, since wet roads barely affect traction
- By half, the same reduction used for packed snow
Wet roads can double stopping distance, so the handbook calls for cutting speed by about a third on a wet road. Packed snow calls for a bigger cut, about half or more, and ice calls for slowing to a crawl.
Hydroplaning, where the tires lose contact with the road on a wet surface, can begin at speeds as low as what?
- 30 mph
- 45 mph
- 55 mph
- 65 mph
It doesn't take much water to cause hydroplaning. The handbook warns it can happen at speeds as low as 30 mph, and it's more likely with low tire pressure or worn tread that can't channel water away.
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.
-
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
What is actually on it
The subjects are set federally, in 49 CFR 383.111, which is why the material barely changes when you cross a state line. You will be asked about inspecting a vehicle, controlling it, managing the space around it, controlling your speed, reading hazards early, handling emergencies and dealing with cargo. Roughly a third of the questions on a real test come down to space and speed management in one form or another, because that is where heavy vehicles differ most from cars.
What catches people out is rarely the obscure material. It is the numbers. How many seconds of following distance you need per ten feet of vehicle. How far a loaded truck travels at 55 mph before it comes to a stop. What blood alcohol level puts you out of service. Those are the questions where a confident guess is usually wrong, and they are the ones this practice test keeps putting in front of you.
How this practice test works
Every time you start, fifty questions are drawn fresh from the bank. You will not get the same fifty twice in a row, and you cannot memorise a fixed order and call that studying. Each question is a separate page, and after you answer, the explanation for what you just did appears at the top of the next one, with the handbook section and page it came from.
That citation is the point. Anyone can write a plausible-looking practice question. A question that names its source is one you can go and check for yourself, and if you think we have it wrong, you have everything you need to tell us so.
At the end you get a breakdown by topic rather than a single score. A driver who is at 90 per cent overall but 40 per cent on air brake material does not need to revise everything again; they need to revise one thing. You can then retry only the questions you got wrong, which is the fastest way to close a gap.
What it will not do
This is not a copy of your state's test. Nobody outside the licensing agency has that, and any site claiming otherwise is guessing. What it does is cover the same federally-required subject areas from the same official material, so that nothing on the real test is a surprise.
Your state's current CDL handbook is always the final word. Read it. Use this to find out which parts of it you have not really absorbed yet.
Also worth reading
Last reviewed September 2026. Sources are re-checked against their publishers once a year.
Questions about this test
How many questions are on the real CDL general knowledge test?
Do I need to pass this before the air brakes or endorsement tests?
How long should I study before booking?
What happens if I fail?
Are the questions here the same as the real ones?
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.
Other tests to take
Ready when you are.
50 questions drawn fresh from 280 cited ones. No account, nothing to pay, and every question in the bank is free.