Combination Vehicles

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Combination Practice Test

Combination Exam


1. To help prevent a rollover load cargo as close to the ground as you can and go slow around turns.

2. A tractor bobtailing takes longer to stop than a loaded combination vehicle.

3. Hand valves should only be used to test trailer brakes.

4. You should not use the hand valve during normal driving, to try and prevent a jackknife.

5. Never use the hand valve as a parking break.

6. The trailer air supply valve supplies air to the trailer air tanks.

7. Color coded air lines are service blue and emergency red.

8. Glad hands hooked together or to dummy couplers keep water and dirty out of the air lines.

9. Many trailers made before 1975 do not have spring brakes.

10. If you cross the air lines on an old trailer without spring brakes, you could pull the trailer but not have any trailer brakes.

11. Breaking an emergency air line will cause the trailer brakes to come on and close the tractor protection valve.

12. When a service air line breaks or comes off, generally nothing happens until the brakes are applied.

13. A fifth wheel must be kept greased to prevent steering problems.

14. Always check that the trailer brakes are locked before backing under a trailer.

15. Always line up directly up in front of a trailer before backing under it.

16. When backing under a trailer, the height is correct when the trailer rises only slightly to hook.

17. Trailer air lines are to be connected before backing under a trailer.

18. After pushing in the trailer supply valve, wait until the air system is at normal pressure before moving the trailer.

19. Make sure the trailer brakes are working by applying and releasing them.

20. After pressurizing the trailer air tanks, set the trailer brakes again before backing under the trailer.

21. After hooking, pull gently on the kingpin with the trailer brakes locked.

22. Always visually check the coupling of combination units.

23. If the fifth wheel locking never did not lock, the coupling is bad and must be fixed.

24. The fifth wheel safety catch must be over the locking lever for a correct coupling.

25. There should be no space between the upper and lower fifth wheels.

26. Fifth wheel jaws should always close around the kingpin shank.

27. Trailer supports or dollies should always be raised fully and the crank handle secure before moving.

28. There must be adequate clearance between the tractor tires and the nose of the trailer.

29. Landing gear and its supports must clear the tractor frame.