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.. 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's 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 have two minutes per question to correctly answer a minimum of 16 questions. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question
Passing Score

1. 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.

2. 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.

3. While inspecting a coupling, you should go under the trailer and:

Explanation
While inspecting a coupling, you should go under the trailer and look into the back of the fifth wheel. Ensure that the fifth wheel jaws are secured around the shank of the kingpin.

4. Pull out the trailer air supply control to test:

Explanation
Be sure to test the trailer emergency brakes before beginning a trip. After ensuring that the trailer rolls freely, you can test the emergency brakes by pulling out the trailer air supply control, or placing it in the "emergency" position. Pull forward slightly with the tractor and make sure the trailer does not move.

5. Look for matching colors when coupling glad hands. Service lines are often:

Explanation
When coupling glad hands, make sure to couple together matching glad hands. To help drivers avoid mistakes, color coding is sometimes used. Service lines are often coded with the color blue and emergency lines are often coded with the color red.

6. Trailers manufactured after ____ must be equipped with Anti-Lock Braking Systems (ABS).

Explanation
Trailers and converter dollies manufactured on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS).

7. The emergency air line:

Explanation
The emergency air line (also known as the supply line) has two functions. The first is to supply air to the trailer air tanks on a combination vehicle, and the second is to control the emergency brakes.
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