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 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
15. When backing a trailer, you must turn the steering wheel:
Explanation
When backing a vehicle with a trailer, you must turn the steering wheel in the direction opposite of where you want to go. Once your trailer starts to turn, you should turn the steering wheel the other way to follow the trailer.
16. If the emergency air line loses pressure:
Explanation
The tractor protection valve keeps air in the trailer's braking system should the trailer break away or develop a leak. A loss of air pressure in the emergency line will cause the tractor protection valve to open and the emergency trailer brakes to activate.
17. If a parked trailer does not have spring brakes, you should keep the trailer from moving by:
Explanation
If a parked trailer does not have spring brakes, wheel chocks should be used to prevent it from moving.
18. In a double or triple combination, the ____ trailer should be directly behind the cab.
Explanation
When positioning trailers in a combination, the most heavily-loaded trailer should be the closest to the tractor. The lightest trailer should be positioned in the rear.
19. Shut-off valves:
Explanation
Shut-off valves are used in air supply lines to control the passage of air from one trailer to another. The rear shut-off valve should always be closed to prevent air from leaving the braking system.
20. What is a bobtail tractor?
Explanation
