How many questions are on the Illinois CDL General Knowledge test?

50 questions. You must answer at least 40 correctly (80%) to pass. This test is required for every CDL applicant regardless of class or endorsement.

How many questions are on the Illinois CDL Air Brakes test?

25 questions, requiring 20 correct (80%) to pass. Required if your vehicle has air brakes.

How many questions are on the Illinois CDL Combination Vehicles test?

20 questions, requiring 16 correct (80%) to pass. Required for Class A CDL applicants who will operate combination vehicles.

What languages are Illinois CDL knowledge tests given in?

English only, though an audio format is available where the computer reads the test aloud. This is a genuine distinction from states that offer testing in multiple languages.

What must I pass before taking any endorsement tests in Illinois?

The General Knowledge test. Illinois requires this before adding any endorsement tests to your CDL application.

Illinois CDL Test Questions 2026: Full Guide

All three Illinois CDL knowledge tests use the same 80% passing threshold. Unlike some states, Illinois tests in English only — but offers a genuinely useful audio format.

General Knowledge Test

50 Questions 40 to Pass (80%) Required for All Applicants

Covers vehicle inspection, basic vehicle control, driving safety, cargo transport, hazardous materials awareness, night driving and adverse conditions, emergency procedures, speed management, and Illinois-specific rules. Required for every CDL applicant, regardless of class or endorsements.

Air Brakes Test

25 Questions 20 to Pass (80%) Required for Air Brake Vehicles

Covers air brake system basics, dual air brake systems, inspecting air brakes, using air brakes correctly, spring brakes and parking brakes, and malfunctions/emergencies. Required if your vehicle has air brakes.

Combination Vehicles Test

20 Questions 16 to Pass (80%) Required for Class A

Covers coupling and uncoupling, inspecting combination vehicles, off-tracking and steering, rollover prevention, skid control and jackknifing, doubles and triples, and antilock brakes. Required for Class A CDL applicants operating tractor-trailer combinations, especially relevant given Illinois' role as a major national freight corridor.

Testing Language

Illinois administers CDL knowledge tests in English only, though an audio format is available where the computer reads the test aloud for accessibility. This is a genuine distinction worth knowing, since some other states offer testing in multiple languages.

Test Sequencing Rule

You must pass the General Knowledge test before taking any endorsement tests, including Air Brakes and Combination Vehicles when treated as prerequisites for further endorsements. Plan your study order accordingly.

Practice All 3 Tests Free

500 real practice questions across General Knowledge, Air Brakes, and Combination Vehicles.

Start Illinois CDL Practice Tests Full CDL Process Guide

Frequently Asked Questions

How many questions are on the General Knowledge test?

50 questions, 40 correct (80%) needed to pass. Required for every applicant.

How many questions are on the Air Brakes test?

25 questions, 20 correct needed. Required for air brake-equipped vehicles.

How many questions are on the Combination Vehicles test?

20 questions, 16 correct needed. Required for Class A applicants.

What languages are the tests given in?

English only, with an audio format available for accessibility.

What must I pass before endorsement tests?

General Knowledge — required before adding any endorsement tests.