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Based on 2025 ON commercial driver's licence manual
Updated for May 2025
FREE Ontario Class D/DZ Licence Test
The Ontario DZ written test is split into two parts: the Class D license knowledge test, and the Z endorsement test for air brakes. The knowledge test for Class D contains 40 multiple-choice questions about large trucks, and combination vehicles along with trucking regulations. There are two sections: 20 questions focused on road rules specific to heavy trucks and commercial vehicles, and 20 questions on associated road signs and trucking signals. The Z endorsement test, which is separate, tests knowledge of air brakes, how they operate, and how to inspect them. Thus, to acquire a DZ license, both the D license test and Z endorsement test must be passed. If you don't pass either test, you can retake the failed one after repaying the associated fees. Looking for a free Ontario DZ practice test? Take this test below for the D license part, and this free Air Brake practice test for your Z endorsement.
Perfect for first-time and renewal commercial applicants, and those adding endorsements
Triple-checked for accuracy
What you need to know
4.78 out of 5 • 9 votes
Verified by Steven Litvintchouk, M.S., Chief Educational Researcher, Member of ACES. See our detailed commitment to accuracy and quality in our practice tests.
Ensuring the accuracy and quality of our program is paramount. Learn more about our rigorous standards in our Commitment to Accuracy article.
In determining how well your air brake system works, which is NOT a significant factor?
Which colour is the trailer supply line?
When is a pre-trip inspection required?
What gauges should you check after starting your vehicle?
Why are there two service tanks in a modern air brake system?
What is the purpose of the National Safety Code?
What does this sign mean?
In Canada, how many classes of dangerous goods are there?
What must you do at a stop sign with a painted stop line?
When brakes become overheated, they also become
What does this sign mean?
Your vehicle is equipped with an air brake system, including a belt-driven air compressor. How do you check for correct belt tension?
What does this sign mean?
Before driving down a grade (hill), you should
What does this sign mean?
Your vehicle has tandem drive axles and is equipped with an inter-axle differential. You should NOT use it if
What does this sign mean?
What is a commercial vehicle's danger zone?
This sign indicates that you may park for one hour
What is the first step of the pre-trip inspection?
In a vehicle equipped with air brakes, the pushrod stroke occurs when compressed air enters the
What is the Gross Vehicle Weight Rating (GVWR)?
Driving a commercial vehicle on the road is
In an air brake system, what does a governor do?
Where are the air brake chambers located?
Our commitment to accuracy and quality in our practice tests
Explore our rigorous, multi-tiered verification process that ensures each question mirrors the official manual for unparalleled accuracy.
Written by Andrei ZakhareuskiUpdated 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.
Content Creation and Verification Process
Alignment with Official Driving Handbooks: Every question we develop is based on the most recent version of each province's official driving manual. Our team regularly monitors each province's official website for the latest updates to ensure our practice tests are always aligned with the most current information.
Community Feedback Integration: 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.
Expert Content Creation: Our in-house editor, Steven, who has extensive experience in driver education, crafts each question with precision. He conducts a thorough review of each question against the official manuals to ensure accuracy.
Rigorous Review Process: Once Steven has finalized a set of questions, our team conducts a joint review session. This second level of scrutiny involves content accuracy, proofreading, and fact-checking to eliminate any errors.
User Feedback Mechanism: After a question goes live on our site, we keep the lines of communication open. Each question features a feedback button, inviting users to report any issues or errors. This continuous feedback loop allows us to address and rectify any concerns promptly.
Responsive Updates: In line with our commitment to accuracy, we quickly update our practice questions to reflect any changes in the provincial government manuals. Additionally, we update the free electronic copy of the state's driver's license manuals on our site, typically within a few days after the government publishes them.
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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