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Free Illinois CDL practice test online

Take a free Illinois CDL practice exam online with clear explanations—no sign-up. Coverage includes general knowledge, vehicle systems, combination vehicles, cargo, and endorsements. Then verify current requirements with Illinois Secretary of State.

CDL knowledge tests are federally regulated, so the passing score in Illinois is the same as everywhere else: 80% correct on every knowledge test. You must also hold a commercial learner’s permit for 14 days before the skills test.

Start practice Exam-style run

New to the knowledge test? CDL endorsements explained · One-week study plan

Practice coverage
Complete a run to establish your baseline.
600questions
23topics
80%federal pass mark

49 CFR 383.135(a)(1) sets the CDL knowledge-test passing score at 80%. Reaching it here is not a prediction of your official result.

Requirements before you test

Illinois CDL test requirements

80%
Passing score
49 CFR 383.135(a)(1)
14 days
CLP held before skills test
Illinois Secretary of State
18
Min. age (in-state)
Illinois Secretary of State
21
Min. age (interstate)
49 CFR 391.11(b)(1)

Commercial licensing is largely federal. Any figure above credited to a 49 CFR section applies in every state — see 49 CFR 383.135(a)(1) and 49 CFR 383.25(e). A figure credited to Illinois Secretary of State is Illinois’s own, and may be stricter than the federal floor. Test length, fees, and scheduling are set by Illinois Secretary of State (official source).

Entry-Level Driver Training comes first

Since February 7, 2022, a new Class A or Class B CDL, a class upgrade, or a first passenger, school bus, or hazardous materials endorsement requires training from a provider on the FMCSA Training Provider Registry (49 CFR 380.600). Practice questions are study material and do not satisfy that requirement.

FMCSA Training Provider Registry

You need a Illinois licence first

A commercial learner’s permit only counts if you already hold an ordinary licence from the same state (49 CFR 383.25(a)(2)). The Illinois non-commercial knowledge test runs 35 questions and needs 28 correct, with permits issued from age 15.

Illinois permit practice test
Quick practice
10 balanced questions with feedback after every answer.
Practice now
Topic review
Focus on one knowledge area before returning to mixed practice.
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Exam-style run
Answer the full starter bank before seeing your results.
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What you will practice

Build coverage topic by topic.

Each question carries a topic, difficulty, explanation, and source section so your review has context.

General knowledge29 reviewed questionsMountain driving12 reviewed questionsAir brakes61 reviewed questionsCombination vehicles54 reviewed questionsVehicle systems9 reviewed questionsCargo18 reviewed questionsTank vehicles47 reviewed questionsDoubles and triples43 reviewed questionsHazardous materials71 reviewed questionsSchool bus48 reviewed questionsPassenger vehicles45 reviewed questionsSafe driving6 reviewed questionsSpace management14 reviewed questionsVehicle inspection15 reviewed questionsEmergencies23 reviewed questionsHours of service14 reviewed questionsBasic control11 reviewed questionsSeeing hazards15 reviewed questionsWeather18 reviewed questionsNight driving7 reviewed questionsDriver fitness8 reviewed questionsSpeed management17 reviewed questionsCommunication15 reviewed questions

Sample questions

5 Illinois CDL practice questions

Try these Illinois sample questions now — each shows the correct answer with a plain-language explanation and a source section. The full 600-question bank is in the practice run.

  1. 1. A 34-hour off-duty period may be used to:

    • Restart a 7- or 8-consecutive-day on-duty period under 49 CFR 395.3(c)
    • BReplace the need for a medical card
    • CCancel all short-haul rules
    • DExtend the 11-hour driving limit mid-day

    Answer: Restart a 7- or 8-consecutive-day on-duty period under 49 CFR 395.3(c). The restart begins with an off-duty period of 34 or more consecutive hours when the rule is used.

    Source: Commercial Driver License Manual — Hours of service — 34-hour restart

  2. 2. When loading packages of hazardous materials, you must never:

    • Use hooks or other tools that could puncture packaging
    • BLoad them against a bulkhead
    • CBrace them with dunnage
    • DUse a pallet

    Answer: Use hooks or other tools that could puncture packaging. A puncture can release the contents inside the trailer. Handle packages carefully and brace them to prevent movement.

    Source: Commercial Driver License Manual — Hazardous materials — loading

  3. 3. Brake drums must not have cracks longer than:

    • One half the width of the friction area
    • BThe full circumference always
    • COne inch regardless of drum size
    • DAny visible mark

    Answer: One half the width of the friction area. Also reject linings that are loose, grease-soaked, or dangerously thin, and hoses that are cut or rubbed.

    Source: Commercial Driver License Manual — Air brakes — walkaround inspection

  4. 4. For tank vehicles you should slow:

    • AOnly at night
    • BAfter you are already in the sharpest part of the turn
    • Before entering curves and ramps, then accelerate slightly through if safe
    • DOnly if empty

    Answer: Before entering curves and ramps, then accelerate slightly through if safe. Posted curve speeds are often too fast for tankers. Partial loads shift most.

    Source: Commercial Driver License Manual — Tank vehicles — curves

  5. 5. During hard braking, an antilock braking system primarily helps a driver:

    • Maintain steering control by reducing wheel lock
    • BIncrease engine power
    • CEliminate the need for following distance
    • DStop instantly

    Answer: Maintain steering control by reducing wheel lock. ABS helps prevent wheel lock. It does not shorten every stop or replace safe speed and spacing.

    Source: Commercial Driver License Manual — Vehicle systems — ABS

Practice all 600 questions

CDL knowledge areas

Classes and endorsements, organized.

Each area below scopes the reviewed question bank to one knowledge test. The material is federal, so it applies in Illinois just like everywhere else — the endorsement guide explains how the codes fit together.

General knowledge

The foundation for commercial driving: inspections, space, speed, communication, hazards, and safe operation.

  • Pre-trip inspection
  • Space and speed management
  • Railroad crossings
  • Emergency procedures
Practice general knowledge
Air brakes

Understand air-brake components, inspections, warning devices, stopping distance, and controlled braking.

  • Dual air systems
  • Low-air warnings
  • Brake lag and fade
  • Applied-leak and static checks
Practice air brakes
Combination vehicles

Prepare for safe coupling, inspection, turning, backing, and handling of tractor-trailer combinations.

  • Fifth-wheel inspection
  • Coupling and uncoupling
  • Off-tracking
  • Trailer skid prevention
Practice combination vehicles
Hazardous materialsEndorsement H

Study hazard communication, shipping papers, placards, loading rules, parking, and emergency response responsibilities.

  • Hazard classes
  • Placards and labels
  • Shipping papers
  • Loading and segregation
Practice hazardous materials
Tank vehiclesEndorsement N

Learn how liquid surge, outage, bulkheads, and high centers of gravity change vehicle handling.

  • Liquid surge
  • Outage requirements
  • Smooth braking
  • Rollover prevention
Practice tank vehicles
Doubles & triplesEndorsement T

Practice converter-dolly inspection, coupling order, rearward amplification, and stability principles.

  • Coupling sequence
  • Converter dollies
  • Rearward amplification
  • Space management
Practice doubles & triples
Passenger vehiclesEndorsement P

Prepare to inspect, load, and operate buses while keeping passengers, aisles, and exits safe.

  • Vehicle inspection
  • Passenger loading
  • Emergency exits
  • Prohibited practices
Practice passenger vehicles
School busEndorsement S

Review student loading, danger zones, mirrors, emergency procedures, and special railroad-crossing duties.

  • Danger zones
  • Student loading
  • Mirror use
  • Railroad crossings
Practice school bus
Official source hub
Verify current rules before your test.

QuizLane’s starter material points learners back to the agency responsible for licensing in Illinois. Rules and manuals can change; the official agency remains authoritative.

Visit Illinois Secretary of State
Our accuracy promise
Original wording—not scraped competitor questions
A source section attached to every reviewed item
A correction path when something looks wrong
Read our methodology

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Common questions

What this practice can—and cannot—tell you.