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. Using the trailer hand valve while driving:
Explanation
Never use the trailer hand valve while operating your vehicle. Using the trailer hand valve while driving can cause your trailer to skid.
16. What is a tractor protection valve?
Explanation
In a combination vehicle with air brakes, the tractor protection valve keeps air in the tractor or truck brake system in the event of the trailer breaking away or developing a leak.
17. 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.
18. If a trailer begins to jackknife, you should not:
Explanation
If a trailer begins to jackknife, you should release the brakes and allow the trailer wheels to regain traction with the road. Do not apply the trailer hand brake to attempt to straighten out the rig because it will only prolong the skid. The application of brakes is what caused the wheels to lock in the first place.
19. If colors are being used to distinguish glad hands, which color is used for emergency lines?
Explanation
When trailer air lines are color-coded, the service lines are generally blue and the emergency lines are generally red.
20. Test the tractor protection valve by:
Explanation
