CDL permit test: what is on it and how to pass
The CDL permit test is a set of multiple-choice knowledge tests at your state licensing agency: General Knowledge for everyone, plus Air Brakes, Combination Vehicles and endorsement tests depending on what you will drive. Federal rules require at least 80 % correct on each test; pass the ones you need and the state issues a commercial learner’s permit (CLP).
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What is on the CDL permit test?
There is no single CDL permit test. It is a group of separate knowledge tests, and you take only those that match the vehicle and the cargo you plan to drive. Every applicant takes General Knowledge, which covers vehicle inspection, basic control, shifting, seeing and communicating, speed and space management, night and winter driving, hazards, emergencies, cargo securement and the rules on drugs, alcohol and fatigue.
On top of that come the tests for your class and your endorsements. States build their tests from a question pool approved by the Federal Motor Carrier Safety Administration (FMCSA), so the topics are the same nationwide even though the wording, the number of questions and some details differ from state to state. Your state’s CDL manual is the reference for exactly what you will be asked.
- General Knowledge: required for every CDL class.
- Air Brakes: needed if your vehicle has air brakes; failing it means an air brake restriction on your permit and license.
- Combination Vehicles: required for Class A (tractor-trailers).
- Endorsements: HazMat (H), Tanker (N), Doubles/Triples (T), Passenger (P) and School Bus (S), each with its own knowledge test.
How many questions are on the CDL permit test?
The number of questions is set by each state, but most use similar test lengths. The pass mark is fixed by federal rule: at least 80 % correct on each knowledge test (49 CFR 383.135). The table shows the usual lengths and how many correct answers that means; check your state’s manual before test day, because a few states use different counts.
| Test | Typical questions | Correct answers needed |
|---|---|---|
| General Knowledge | 50 | 40 |
| Air Brakes | 25 | 20 |
| Combination Vehicles | 20 | 16 |
| Hazardous Materials | 30 | 24 |
| Tanker, Doubles/Triples, Passenger, School Bus | 20 each | 16 each |
Which CDL permit tests do I need for Class A, B or C?
Your class depends on the weight rating of what you drive (49 CFR 383.91). Class A covers combinations of 26,001 lb or more where the towed unit is rated over 10,000 lb, such as a tractor-trailer. Class B covers a single vehicle of 26,001 lb or more, such as a straight truck, dump truck or city bus. Class C covers smaller vehicles that carry 16 or more people including the driver, or placarded hazardous materials.
A Class A license also lets you drive Class B and C vehicles if you hold the endorsements those vehicles need, so many drivers aim for Class A from the start. Remember that a hazardous materials endorsement also needs a federal security background check, and HazMat is not allowed on a learner’s permit at all.
| Goal | Knowledge tests |
|---|---|
| Class A tractor-trailer | General Knowledge, Combination Vehicles, Air Brakes |
| Class B straight truck | General Knowledge, Air Brakes |
| Class B or C bus | General Knowledge, Passenger, Air Brakes if equipped |
| School bus | General Knowledge, Passenger, School Bus |
| Tank, doubles or HazMat work | Add Tanker, Doubles/Triples or HazMat |
What happens after you pass the CDL permit test?
Once you pass, the state issues a commercial learner’s permit. With a CLP you may practice in a commercial vehicle on public roads only while a CDL holder with the right class and endorsements sits next to you (49 CFR 383.25). You must be at least 18 to hold a CLP, and federal rules require you to be 21 to drive across state lines.
The CLP is valid for no more than one year from the date it was first issued, and you may not take the skills test in the first 14 days after it was issued. Before the skills test for a first Class A or B license, and before adding a Passenger, School Bus or HazMat endorsement for the first time, you must also finish entry-level driver training with a provider listed in FMCSA’s Training Provider Registry (49 CFR 380.609).
- Read your state’s CDL manual and get a DOT medical card if your state requires one for your type of driving.
- Pass General Knowledge and the class and endorsement tests you need: that gets you the CLP.
- Complete entry-level driver training with a registered provider and practice with a qualified CDL holder.
- After at least 14 days, take the three-part skills test: vehicle inspection, basic control and the road test.
How do you study for the CDL air brakes test?
Air Brakes is the test where many applicants lose points, because it asks for numbers. Learn the parts (compressor, governor, tanks, drains, slack adjusters, spring brakes) and the values of the in-cab check, which you will also have to perform and say out loud during the vehicle inspection part of the skills test. The values below are the ones state manuals commonly teach; some differ, so learn the numbers in your own state’s manual.
- Take practice tests until you score clearly above 80 %, not just at it: the real test mixes the questions differently.
- Every wrong answer is a topic to re-read in the manual, not only a question to memorize.
- If you fail, states must give you a different version of the test when you retake it, so learning the subject beats learning answer patterns.
| Check | What to look for |
|---|---|
| Governor cut-out / cut-in | Compressor stops around 125 psi and starts again around 100 psi |
| Pressure build-up (dual air system) | From about 85 to 100 psi within 45 seconds |
| Leak-down, brakes released | Loss under 2 psi in 1 minute (single vehicle), 3 psi (combination) |
| Leak-down, brakes applied | Loss under 3 psi in 1 minute (single vehicle), 4 psi (combination) |
| Low-air warning | Before pressure drops below about 60 psi; California’s manual says 55 psi |
| Spring brakes | Apply on their own, usually between 20 and 45 psi |
How Rigvo helps you prepare for the CDL permit test
Rigvo is a CDL study app for Android that covers all eight knowledge tests: General Knowledge, Air Brakes, Combination Vehicles, HazMat, Tanker, Doubles/Triples, Passenger and School Bus. The questions are written by the Rigvo team; 219 of them link to the federal rule in 49 CFR they rest on, the rest cover general commercial driving practice.
- Practice mode shows right away whether you were correct and explains why, with the rule or driving fact as source; you can report an error from any question.
- Exam simulator with typical test lengths: 50 questions for General Knowledge, 25 for Air Brakes, 30 for HazMat and 20 for the others, with 80 % to pass and the results at the end.
- Pass chance: an estimate of your chance to pass today based on everything you have answered, plus the topics that hold you back.
- Weak-spots drill: questions you miss come back until you know them.
- Pre-trip inspection trainer, zone by zone, with what to check and a line to say out loud; drill mode hides the line until you have said it yourself.
- In-cab air brake check step by step with the value each step must meet: leak-down, low-air warning, spring brakes, governor and build-up.
What the app cannot do
Rigvo is an independent study app and is not affiliated with FMCSA, AAMVA, the U.S. Department of Transportation or any state DMV; it cannot book or replace your official test and does not guarantee a pass. Test length, pass marks and some rules differ by state, so your state’s CDL manual remains the reference. The app is in English and available for Android only.
Price
Free to try with 50 General Knowledge questions, one full General Knowledge mock exam, 3 sample questions for each other test and the first pre-trip zone; Rigvo Pro unlocks all 700 questions and the full trainers as a monthly ($14.99) or yearly ($99.99) subscription through Google Play in the US. We build this app ourselves; on Google Play it is listed under the developer name InfinityAkhi.
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Frequently asked questions
What score do you need to pass the CDL permit test?
At least 80 % on each knowledge test, set by federal rule. On a typical 50-question General Knowledge test that means 40 correct answers; on a 25-question Air Brakes test, 20.
How long is a CDL learner’s permit valid?
No more than one year from the date it was first issued. A state may issue it for a shorter time and renew it, but not beyond one year in total without retaking the knowledge tests.
How soon after the permit can I take the CDL skills test?
Not within the first 14 days after the CLP was issued. For a first Class A or B license you also need to have completed entry-level driver training with a registered provider.
What happens if I fail the air brakes test?
You can still get your permit, but it will carry an air brake restriction, so you may not drive vehicles with air brakes. To remove it later you pass the air brake knowledge test, do the air brake part of the inspection and, if your state asks for it, a short modified skills test.
Are the questions in Rigvo the official test questions?
No. The official question pool is not public. Rigvo uses its own questions on the same topics, many of them linked to the federal rule they are based on.
Sources
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