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ON Air Brake Test 4 2024

4.67 out of 5 • 3 votes.
Based on 2024 ON commercial driver's license manual Instant feedback

Do you want to drive a truck in Ontario? To be a commercial driver in this province, you need a licence that is specific to the type of truck you want to drive. As a truck driver, you are a critical part of the transportation industry. The power and size of large trucks are awe-inspiring. Even while you’re driving safely, the smallest mistake can cause serious damage. Before you can get your commercial driver’s licence, you must pass both a written and practical test. The written test (also known as the Ontario commercial driver’s licence knowledge exam) has several multiple-choice questions. You must get at least an 80% to pass the knowledge examination. This 50-question practice test will help you to prepare for the Ontario (ON) Air Brake written test required to get your commercial driver’s licence. As you answer the questions on this test, we recommend checking each question’s explanation to gain further insight into the rule behind it. All questions on this test are based on the 2024 ON commercial driver’s guide. Good luck and drive safely!

Ensuring the accuracy and quality of our practice tests is paramount. Learn more about our rigorous standards in our Commitment to Accuracy article.

Perfect for:

  • First-time ON commercial license applicants
  • Existing commercial license holders adding endorsements
  • ON commercial license renewal applicants

What to expect on the actual ON commercial license exam:

  • 25 questions
  • 20 correct answers to pass
  • 80% passing score

More FREE ON Commercial Driving Resources:

  1. General Knowledge 1
  2. General Knowledge 2
  3. General Knowledge 3
  4. General Knowledge 4
  5. General Knowledge 5
  6. General Knowledge 6
  7. General Knowledge 7
  8. Road Signs
  9. Road Signs 2
  10. General Knowledge Marathon
  11. General Knowledge Exam Simulator
  12. Class A Licence Test 1
  13. Class A Licence Test 2
  14. Class A Licence Test 3
  15. Class A Licence Marathon
  16. Class A Licence Exam Simulator
  17. Class B Licence Test 1
  18. Class B Licence Test 2
  19. Class B Licence Test 3
  20. Class B Licence Test 4
  21. Class B Licence Test 5
  22. Class B Licence Test 6
  23. Class B Licence Test 7
  24. Class B Licence Test 8
  25. Class B Licence Test 9
  26. Class B Licence Test 10
  27. Class B Licence Test 11
  28. Class B Licence Marathon
  29. Class B Licence Exam Simulator
  30. Class C Licence Test 1
  31. Class C Licence Test 2
  32. Class C Licence Test 3
  33. Class C Licence Test 4
  34. Class C Licence Test 5
  35. Class C Licence Test 6
  36. Class C Licence Test 7
  37. Class C Licence Test 8
  38. Class C Licence Test 9
  39. Class C Licence Test 10
  40. Class C Licence Test 11
  41. Class C Licence Marathon
  42. Class C Licence Exam Simulator
  43. Class D Licence Test 1
  44. Class D Licence Test 2
  45. Class D Licence Test 3
  46. Class D Licence Marathon
  47. Class D Licence Exam Simulator
  48. Class F Licence Test 1
  49. Class F Licence Test 2
  50. Class F Licence Test 3
  51. Class F Licence Test 4
  52. Class F Licence Test 5
  53. Class F Licence Test 6
  54. Class F Licence Test 7
  55. Class F Licence Marathon
  56. Class F Licence Exam Simulator
  57. Air Brake Test 1
  58. Air Brake Test 2
  59. Air Brake Test 3
  60. Air Brake Test 4 (you are here)
  61. Air Brake Test 5
  62. Air Brake Test 6
  63. Air Brake Test 7
  64. Air Brake Test 8
  65. Air Brake Test 9
  66. Air Brake Test 10
  67. Air Brake Test 11
  68. Air Brake Test 12
  69. Air Brake Test 13
  70. Air Brake Test 14
  71. Air Brake Marathon
  72. Air Brake Exam Simulator
  73. AZ Licence Exam Simulator

List of questions (classic view)

  1. How often should the air tanks be drained?
  2. On a tractor-trailer, if the supply and service lines to the trailer are cross-connected, what may happen?
  3. How do you release DD3 safety actuator brakes?
  4. When you're going to tow a trailer, how can you tell if the trailer's antilock braking system (ABS) is working?
  5. Wedge brakes are
  6. The purpose of the tractor protection valve is
  7. To test the tractor protection valve, disconnect the trailer service line and
  8. In a tractor-trailer, the connections between the tractor and the trailer include which of the following components?
  9. The hand valve control ("spike") applies
  10. Which brakes are more powerful, the spring brakes or the service brakes?
  11. Which of the following is NOT a part of a truck's braking system?
  12. A tractor-trailer's braking system supplies compressed air to which trailer brakes FIRST?
  13. An S-cam is found in
  14. When coupling a tractor to a trailer, how many air lines do you have to connect?
  15. If there is a loss of air to the service brakes in a trailer with a spring brake priority system, how can you brake the trailer to a stop?
  16. In a trailer with a spring brake priority system, compressed air is supplied to which brakes FIRST?
  17. How many air lines must be connected to a DD3 safety actuator brake chamber?
  18. The tractor protection valve closes to stop the flow of compressed air to
  19. To uncouple your tractor from the trailer, how should you set the trailer air supply valve?
  20. Which of the following is not a component of a wedge brake?
  21. How often should you check brake chamber pushrod travel?
  22. Which of the following is a part of a disc brake?
  23. In an air braking system, which of the following is not commonly part of a disc brake?
  24. Which of the following are helpful in reducing heat in the air brake system?
  25. Which of the following can affect pushrod stroke?
  26. If you find a major defect in the air brake system, you should
  27. How can you determine applied pushrod stroke?
  28. Which is least likely to cause brake drums to overheat?
  29. When must full braking capability be available?
  30. Assuming good traction and constant vehicle weight, if you double your vehicle's speed, your vehicle's braking distance will be
  31. In an air brake system, what does a governor do?
  32. Which of the following is the best way to inspect an air compressor?
  33. When can you adjust automatic slack adjusters?
  34. If the outer layer of an air line is damaged, but the inner tube is still OK, what should you do?
  35. To make sure the air tanks are securely attached to your vehicle, you should
  36. Before inspecting your air brakes, you should
  37. Your vehicle passes the tug test of the parking brakes if
  38. If the brake chambers on opposite sides of an axle are of different sizes, the result may be
  39. To check the brake chambers for leaks, you should
  40. in a drum brake, the brake lining is fastened to
  41. What occurs when the brake drums undergo excessive heating?
  42. Normal air brake tank pressures are
  43. What letter is added to your licence when you apply for an Air Brake Endorsement?
  44. What mechanism drives the air compressor?
  45. What should you do if your brakes overheat due to continual use or improper adjustment?
  46. What term refers to the pressure level at which the air compressor stops pumping air?
  47. The pressure range of the normal air brake system is dictated by the points at which the air compressor ...
  48. Cut-in pressure should never be less than
  49. Can brake fluid compress similarly to air in air brake systems?
  50. What role does the air compressor play?