Combination

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial Driver License.. Read More

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial Driver License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question
Passing Score

8. If a load is placed on one side of a trailer, the trailer:

Explanation
If the weight of a load is placed primarily one side of a trailer, the trailer may lean, increasing the risk of a rollover.

9. When lightly loaded, combination vehicles:

Explanation
When a combination vehicle is lightly loaded, it may have poor traction. It is very easy for wheels to lock up on lightly-loaded vehicles when they are being stopped.

10. A tractor protection valve is:

Explanation
On combination vehicles with air brakes, the tractor protection valve keeps air in the tractor or truck brake system, should the trailer develop a bad leak or break away from the tractor.

11. Failure to keep the fifth wheel plate properly greased could:

Explanation
Failure to keep the fifth wheel plate properly lubricated can create friction between the tractor and trailer, causing steering problems.

12. When a combination vehicle goes around a corner:

Explanation
When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called off-tracking. This effect is especially pronounced on vehicles with trailers.

13. What does the trailer air supply control look like?

Explanation
On newer vehicles, the trailer air supply control is an eight-sided red knob. It's used to control the tractor protection valve.

14. What is a bobtail?

Explanation
Tractors without semi-trailers are referred to as bobtail tractors. Operating a bobtail tractor requires drivers to exercise caution.
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