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. During a trip, which shut-off valves should be open?

Explanation
When starting a trip, be sure that all shut-off valves are in the open position, except for the last valves on the rear trailer. It is important that air reaches the brakes on all trailers and that the air is not able to escape from the back of the vehicle.

9. When connecting a converter dolly to a second or third trailer, the trailer height should be:

Explanation
When connecting a converter dolly to a second or third trailer, the trailer height should be correct. It should be slightly lower than the center of the fifth wheel.

10. 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.

11. Trailers with low underneath clearance may be difficult to drive:

Explanation
Railroad-highway crossings may be difficult to cross when pulling a trailer with a low underneath clearance. In particular, both low-slung units and single-axle tractors pulling long trailers are especially challenging to drive over raised crossings.

12. When coupling a trailer:

Explanation
When coupling, make sure you couple matching glad hands. They are often color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

13. When driving a bobtail tractor, you should be aware that:

Explanation
Bobtail tractors are tractors that are not attached to any semitrailers. When operating a bobtail, you should be aware that stopping can be difficult and that it will take a longer distance to bring the bobtail to a complete stop than it would a tractor attached to a loaded semitrailer.

14. How many air lines does a combination vehicle have?

Explanation
Every combination vehicle has two air lines: the service line and the emergency line.
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