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  • Based on 2024 ON commercial driver's licence manual
  • Updated for December 2024

If you want to drive a truck in Ontario, you need a commercial truck driver’s licence. With a commercial driver’s licence, you can work for a trucking company as an employee or work for yourself as an owner-operator. The transportation industry in Ontario is booming, and truck drivers are in high demand. As a driver of one of the largest vehicles on the road, you must study and practice to learn to drive carefully and safely. Before you can get your commercial driver’s licence, you must pass both a written and a practical test. The written test (also known as the Ontario truck driver’s licence knowledge exam) has several multiple-choice questions. You must get at least an 80% to pass the knowledge exam. The knowledge test for each class of licence typically takes approximately 30 minutes. For the practical test, you will meet with an examiner to demonstrate your knowledge of the operation of a truck. The official Commercial Driver’s Handbooks are great resources, but they lack practice. This 20-question ON Air Brake practice test is a great way to start as it covers the basics of commercial driving in Ontario. All questions are based on the official 2024 ON commercial driver’s manual. As you answer the questions, we recommend checking each question’s explanation to gain some further insight into the rule behind it. Good luck and drive safely!

  • Perfect for first-time and renewal commercial applicants, and those adding endorsements
  • Triple-checked for accuracy
What you need to know
Verified by Steven Litvintchouk, M.S., Chief Educational Researcher, Member of ACES. See our detailed commitment to accuracy and quality in our practice tests.
What to expect on the official exam
20

questions

16

correct answers to pass

80

passing score

List of questions (classic view)
  1. Should you pump (keep pressing and releasing) air brakes?
  2. It is important to keep compressed air as dry as possible because
  3. What does the low air pressure warning device warn you about?
  4. If the low air pressure warning signal comes on, what should you do?
  5. The effectiveness of the spring brakes for emergencies or parking
  6. During normal driving, what keeps the spring brakes released?
  7. Assuming good traction and constant vehicle weight, if you double your speed, your vehicle's braking distance will be
  8. If drum brakes overheat, the vehicle's stopping distance will increase. What is the reason for this?
  9. Air braking systems tend to react slower than hydraulic braking systems because
  10. While travelling downhill, you notice that each time you want to brake, you must press the brake pedal farther down than the last time to achieve the same braking force. What could be causing this?
  11. The maximum air pressure available for braking is determined by
  12. The foot (treadle) valve
  13. Which of the following can impair braking effectiveness?
  14. After you apply the service brakes, what happens to that compressed air?
  15. What does an alcohol evaporator do?
  16. When you test the system air-loss rate, the maximum acceptable leakage rates per minute after the initial drop are
  17. You're driving a vehicle equipped with a dual air brake system. The low air pressure warning signal comes on, but one system still has normal pressure. What should you do?
  18. How should you test your vehicle's low air pressure warning signal?
  19. An application pressure gauge shows the air pressure
  20. All vehicles equipped with air brakes must have
  21. What is the colour coding that is often used for the supply and service lines to the trailer?