Illinois CDL practice test
To get a commercial learner's permit in Illinois you pass the Illinois Secretary of State knowledge tests for your vehicle class and endorsements. The tests are based on the state's commercial driver manual; our CDL practice tests follow the same national model manual that Illinois's manual is based on.
Illinois CDL knowledge tests
| Test | Questions | To pass |
|---|---|---|
| General Knowledge (core) | 30 | 80% |
| Combination Vehicles | 20 | – |
| Air Brakes | 25 | – |
| Passenger (P) | 20 | – |
| Tank Vehicle (N) | 20 | – |
| School Bus (S) | 20 | – |
| Hazardous Materials (H) | 30 | – |
| Doubles/Triples (T) | 20 | – |
| Charter Bus (C, Illinois) | 20 | – |
"–" means the Secretary of State doesn't publish the figure.
Getting a CDL in Illinois
- Decide your class (A, B or C) and endorsements, and read those sections of the manual.
- Pass the knowledge tests at the Secretary of State to get your commercial learner's permit (CLP). Federal rules also require a medical certificate for most drivers.
- Hold the CLP for at least 14 days. First-time Class A and B applicants, and anyone adding the passenger, school bus or hazmat endorsement, must finish entry-level driver training with a provider on the FMCSA Training Provider Registry before the skills test.
- Pass the skills test: pre-trip inspection, basic control and an on-road drive.
You must be at least 21 to drive a commercial vehicle across state lines or carry hazardous materials that need placards. More about CDL classes and tests.
Practise for each test
- General knowledgeRequired for every CDL: inspection, vehicle control, space and speed, hazards, emergencies, cargo.
- Air brakesNeeded to drive vehicles with air brakes; without it you get an air brake restriction.
- Combination vehiclesFor tractor-trailers and other combinations (Class A).
- Hazardous materialsFor the H endorsement; also needs a TSA background check.
- Tanker vehiclesFor the N endorsement: liquids and gases in bulk.
- Passenger transportFor the P endorsement: buses and vehicles for 16 or more people.
- School busFor the S endorsement, together with the passenger endorsement.
- Doubles and triplesFor the T endorsement: pulling two or three trailers.
Which tests do you need?
- Everyone: general knowledge.
- Tractor-trailers and other Class A combinations: combination vehicles, plus air brakes if the vehicle has them.
- Buses: passenger transport, and school bus for school buses.
- Endorsements: hazardous materials (H), tank vehicles (N) and doubles/triples (T) each have their own test.
If you don't pass the air brakes test, your CDL gets an air brake restriction.
The Illinois CDL manual
Download the official commercial driver manual from the Illinois Secretary of State, Driver Services Department. Read the sections for the tests you're taking.
The general knowledge test has 30 standardized multiple-choice questions, and you need at least 80% to pass. Written tests are valid for up to one year. Interpreters are not allowed for CDL tests. CDL tests are in English; the SOS announced a Spanish-language CDL written test in July 2024. Check with the SOS before you go.
Source: Illinois Secretary of State, Driver Services Department, checked 2026-10-27.