ON Air Brake Test 3

Driving a commercial vehicle is very different from driving a car. Trucks have different controls and different blind spots. As a commercial vehicle operator, you must travel long distances and face a variety of traffic and weather conditions. You must also be prepared to deal with emergencies such as fires and collisions. Before you can get your commercial driver’s licence in Ontario, you must study and practice to learn to drive carefully and safely. To get your commercial driver’s licence, you must pass both a written and a practical test. The written test (also known as the truck driver’s licence knowledge exam) has several multiple-choice questions. If you are looking for a practice test before taking the commercial driver’s licence knowledge test, this is the place. This practice test will help you prepare. Please note that this is a sample test and does not replace the official truck driver’s knowledge exam. There are 49 questions with hints and explanations of the correct answer. All questions are based on the official 2025 ON commercial driver’s manual. If you have any questions or comments, please contact us. Good luck!

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Written by Andrei Zakhareuski Updated over a week ago

At Tests.ca, we understand the importance of reliable and accurate practice tests to help you prepare for your driver's knowledge exam. That's why we've developed a meticulous process to create and continually update our practice questions, ensuring they reflect the most current driving laws and regulations.

Here's an inside look at how we maintain the highest quality in our practice tests.

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We leverage feedback from our vast community of users to understand which topics are most frequently tested. This helps us focus on the areas that are most relevant and beneficial for your preparation.
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Our thorough quality control process ensures that you have access to practice tests that are as accurate and up-to-date as possible. We believe in the power of well-prepared drivers and are dedicated to providing you with the best study tools to help you succeed on your driver's knowledge exam.

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List of questions (classic view)

The air compressor should be inspected only when
For the air brake inspection, what do you check first?
In an S-cam drum brake, which of the following is connected to the brake spider?
A brake shoe is not a part of
Brake chambers are found on
It does not matter if a small amount of oil is discovered during drainage of
Compressed air from the air compressor first goes to the
Compressed air exhaust is
Compressed air entering the brake chambers applies
Evacuating air from the brake chambers will apply
A brake lining that has become contaminated with oil or grease indicates a problem with the
An air line shows signs of wear from rubbing, but there are no leaks because the inner tube is still in good shape. What should you do?
An alcohol evaporator or air dryer can
Which tank is likely to collect the most moisture?
Your vehicle will fail the air tank drain valve test if
There is a split-second delay in activation of _________. There is no delay in activation of _________.
The braking system converts the kinetic energy of the moving vehicle into
When you drain the air tanks, which tank should you drain first?
What is the purpose of the governor?
The air compressor is powered by the
Air pressure monitoring gauges are located on the _________ of the vehicle.
The pushrod stroke occurs when compressed air enters
When you press the brake pedal, the valve underneath the brake pedal ________ to apply the service brakes.
Which of the following is part of a disc brake?
If the low air pressure warning signal comes on, what should you do?
In a tractor-trailer, an anti-compounding valve is connected to
In Canada, automatic slack adjusters have been installed on trucks and trailers manufactured since
When you use the free stroke (pry bar) method, the pushrod should not move more than
If your vehicle is equipped with automatic slack adjusters, why must you fully apply the service brakes regularly?
In Canada, antilock braking systems (ABS) have been mandatory on all trucks and buses over 4,560 kg that have been manufactured since
Which of these significantly decreases the braking force produced at the wheel?
Which type of trailer can be towed before the service tanks are full?
In determining how well your air brake system works, which is NOT a significant factor?
In large commercial vehicles, most air brake systems use automatic valves to
Where are a vehicle's air tanks located?
What is the "cut-in" level?
Normally, who can adjust automatic slack adjusters?
Which statement is true of spring brakes?
Which colour coding is usually employed for the service line?
Why are there two service tanks in a modern air brake system?
What is a "glad hand"?
What function does the alcohol evaporator perform?
To inspect an air brake system, you should wear
When must you chock the wheels of your stopped vehicle?
Finding a small bit of oil during an inspection is NOT serious if it's coming from
When inspecting the brake chambers, you should check for which of the following?
Cut-in pressure must never be lower than
What colour is the parking brake control button?
In an air brake system, spring brakes are intended for
The pushrod stroke occurs when compressed air enters the