Free, full Illinois CDL general knowledge test practice right here in your browser — real exam format (50 questions, 80% to pass), diagnostic and adaptive modes, spaced-repetition review, and a readiness dashboard. No signup, no paywall — your progress is saved automatically on this device. Matched to the official SOS knowledge exam.
What does a CDL Medical Examiner's Certificate (MEC) prove?
B. That the driver meets the physical qualifications required to operate a CMV under 49 CFR Part 391 — The Medical Examiner's Certificate (Form MCSA-5876) confirms that the driver has been examined by a certified medical examiner and meets the physical qualification standards in 49 CFR Part 391.
When checking lighting during a vehicle inspection, which lights must work at all times on a CMV?
B. All marker lights, clearance lights, identification lights, and brake lights — all required lighting must work — Federal regulations require all lights on a CMV to be in proper working order, including required marker lights, clearance lights, identification lights, headlights, brake lights, and turn signals.
The air compressor is connected to the engine through:
D. Gears or a V-belt — The air compressor is driven by the engine through gears or a V-belt and pumps air into the air storage tanks.
What is a 'converter dolly' used for in a combination vehicle?
B. To connect a second semi-trailer to the first trailer, allowing it to follow the first trailer — A converter dolly (or converter gear) is a one- or two-axle unit with a fifth wheel that connects a second semi-trailer to the rear of the first trailer, creating a doubles combination.
A first conviction for driving a CMV while using a controlled substance results in disqualification for at least:
A. One year — A first major offense such as driving under the influence disqualifies a CDL holder from operating a CMV for at least one year.
Under HOS rules, after 8 consecutive hours of driving, you must take a break of at least:
D. 30 minutes — After accumulating 8 hours of driving, federal HOS rules require at least a 30-minute off-duty break before driving again. The break can be taken as a sleeper berth period. Skipping it extends fatigue and violates regulations that can result in an out-of-service order.
Off-tracking in a doubles combination means:
B. The tendency for the rear trailer's wheels to track inside the front trailer's path in turns — Off-tracking occurs when rear wheels in a combination take a shorter path than the front wheels during a turn. In a doubles or triples combination, off-tracking is greater, requiring wider turns.
If your brakes fail on a long downgrade, your best escape is usually to:
B. Use an escape ramp if one is available — An escape ramp is designed to stop a runaway vehicle safely, making it the best option when brakes fail on a long downgrade.
Before backing under the trailer, make sure the:
C. Trailer brakes are locked and/or wheels are chocked — The trailer brakes should be locked (or wheels chocked) to prevent the trailer from moving when backing under.
What is the FMCSA's definition of a 'commercial motor vehicle' (CMV) for CDL purposes?
B. A vehicle with a GVWR of 10,001 lbs or more, OR designed to carry 16+ passengers, OR transporting placardable hazardous materials — A CMV (for CDL licensing purposes) includes: vehicles with a GVWR or GCWR of 26,001+ lbs (CDL-A/B), vehicles designed to carry 16+ passengers including driver (CDL-B/C), or vehicles transporting placardable HazMat (CDL-C).
The Illinois CDL general knowledge test has 50 questions, and you need 80% to pass — at least 40 correct answers. The practice tests on this page use the same format. The 80% passing score is a federal FMCSA standard used by every state.
80%. You can miss at most 10 of the 50 questions. The readiness dashboard on this page tracks whether you're consistently scoring above that bar.
In Illinois, driver licensing is handled by the Illinois Secretary of State (SOS), so you'll often see the exam called the SOS CDL general knowledge test. The practice tests on this page match the official SOS knowledge exam format.
Yes. Every practice test on this page and everything in the DMVPrep iPhone app is free — no ads, no paywall, no account.
Federal motor carrier safety regulations (FMCSA) — the same rules every state's CDL exam is drawn from. Every question in the DMVPrep app cites the regulation or handbook section it comes from.
Yes — the DMVPrep app includes all 3,745+ questions in Spanish, and the whole app works in Spanish.