# 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..

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. What happens when the wheels of a trailer lock up?

Explanation
A trailer may swing out and strike other vehicles if its wheels lock up. This is especially likely with lightly-loaded trailers.

### 9. 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.

### 10. If your vehicle gets stuck on railroad tracks, you should:

Explanation
If your vehicle gets stuck on railroad tracks for any reason, you should immediately exit the vehicle and walk away from the tracks. Contact the proper emergency authorities.

### 11. If color-coded, which color is used to identify service lines?

Explanation
Air lines are sometimes color-coded to help drivers avoid mistakes when coupling glad hands. Typically, blue is used for service lines and red is used for emergency lines.

### 12. 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.

### 13. Combination vehicles need extra space on the road because they:

Explanation
Combination vehicles need more space on the road than other commercial vehicles because they are longer and need more space to turn and stop. It is especially important to properly manage space when you are operating a combination vehicle.

### 14. The service air line is attached to the:

Explanation
The service air line carries air and is controlled by either the foot brake or trailer hand brake. The service air line is attached to relay valves, which allow the trailer brakes to be applied quickly.