The core tests
This site covers the three core knowledge tests for a Class A CDL: General Knowledge, Air Brakes and Combination Vehicles.
The Air Brakes test decides what you may drive: if you fail the air brake knowledge test, or take the skills test in a vehicle without air brakes, your license is restricted from vehicles with any type of air brakes.
Passing score
Federal rules require at least 80 percent correct answers on every knowledge test. On a test with 50 questions, for example, you need 40 correct.
Endorsements
Endorsements let you drive specific vehicles or loads. Each needs its own knowledge test, and two of them also need a skills test:
- Doubles/Triples (T): knowledge test
- Tank Vehicles (N): knowledge test
- Hazardous Materials (H): knowledge test
- Passenger (P): knowledge test and skills test
- School Bus (S): knowledge test and skills test
The commercial learner's permit (CLP)
With a passed general knowledge test you can get a CLP. You must be at least 18 and hold a valid driver's license from the same state. The CLP is valid for no more than one year, and you always drive with a CDL holder of the right class and endorsements in the front seat.
You cannot take the CDL skills test in the first 14 days after your CLP is issued. A CLP can carry only the Passenger, School Bus and Tank Vehicle endorsements, a tank vehicle must be empty, and you may not transport hazardous materials.
How to prepare
Start with General Knowledge, then Air Brakes and Combination Vehicles, then the endorsements you need. Each practice test on this site has 30 questions from one subtest and is scored against 80 percent.
Frequently asked questions
What score do I need to pass a CDL knowledge test?
To pass a CDL knowledge test, you need at least 80 percent correct answers on each test.
How many questions are on the general knowledge test?
Your state sets the number of questions on the CDL general knowledge test. The 80 percent passing score applies in every state.
Which endorsements need a skills test?
The Passenger and School Bus endorsements need a skills test as well as a knowledge test. Doubles/Triples, Tank Vehicles and Hazardous Materials need only a knowledge test.
How soon after getting my CLP can I take the skills test?
You cannot take the CDL skills test in the first 14 days after your CLP is issued.
Can I haul hazardous materials with a CLP?
No, CLP holders may not transport hazardous materials.
Sources
- 49 CFR 383.135, passing knowledge and skills tests (Cornell LII)
- 49 CFR 383.93, endorsements (Cornell LII)
- 49 CFR 383.25, commercial learner's permit (Cornell LII)
- 49 CFR 383.95, restrictions (Cornell LII)
Updated: November 2026