CDL Written Test Study Guide

Passing the CDL written test on your first attempt is absolutely achievable — if you study the right material and practice with realistic questions. Most drivers who fail do so not because the test is hard, but because they didn't prepare properly.

What Is on the CDL Written Test?

There are four written knowledge tests, depending on your license class and endorsements:

• General Knowledge — Required for all CDL applicants. 50 questions, 80% to pass.
• Air Brakes — Required if you drive a vehicle with air brake system. 25 questions.
• Combination Vehicles — Required for Class A. Covers coupling, rollover prevention, jackknife recovery.
• Pre-Trip Inspection — Tests your knowledge of vehicle safety checks.

The 5 Biggest Mistakes Drivers Make

1. Skipping practice tests. Reading the handbook is not enough. You need to practice with test-like questions to learn the format and timing.
2. Ignoring Air Brakes specifics. Brake lag (adding ~32 feet at 55 mph), dual air systems, and spring brake activation — these are the most failed topics.
3. Not knowing weight limits. Steer axle: 12,000 lbs. Drive axles: 20,000 lbs. Tandem: 34,000 lbs. These numbers appear on every test.
4. Confusing CDL classes. Class A: GCWR 26,001+ lbs with trailer over 10,000 lbs. Class B: single vehicle 26,001+ lbs.
5. Forgetting HOS rules. 11-hour driving limit, 14-hour window, 30-minute break requirement.

Study Schedule That Works

Week 1: Read the CDL handbook. Focus on General Knowledge sections. Take notes on the numbers.

Week 2: Practice General Knowledge questions daily. Review explanations for every wrong answer.

Week 3: Air Brakes and your endorsement areas. Take full practice tests under timed conditions.

How to Use Practice Tests Effectively

Don't just take tests — study them. For every question you get wrong, write down why the correct answer is right. The explanations in our practice tests are designed to teach, not just score you.

Take the test in hard mode — where the wrong answers are designed to be plausible. This is how the real exam feels.