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Commercial Driver’s License (CDL) Exam Endorsement Test: The Combination Vehicles Test
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Commercial Driver’s License (CDL) Exam Endorsement Test: The Combination Vehicles Test
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25 Questions

1. What are the two purposes of the emergency air line on combination vehicles
2. Which of the following is the correct definition of offtracking
3. If the service and emergency air lines are crossed when hooking up an old trailer, what will happen
4. The “normal” position of the trailer air supply control is used for
5. Your trailer has begun to skid. You should
6. When should the trailer hand valve be used
7. The earliest and best way to recognize that your trailer has started to skid is by
8. Fully loaded rigs are ________________ times more likely to rollover in a crash than empty rigs.
9. What will happen if the service air line comes apart while you are driving a combination vehicle
10. You are coupling a tractor and semitrailer, and ready to back your trailer under a semi-trailer. When is the trailer at the right height
11. When coupling a tractor and semitrailer, you must lock the kingpin into the fifth wheel. Which is the best way to check the connection
12. Emergency lines on combination vehicles are often color coded to keep them from getting mixed up. The service lines are coded with the color __________, and the emergency lines are coded with the color __________ .
13. The tractor protection valve will close automatically if air pressure is low or in the range of
14. Which of the following reduces the risk of rollover
15. To supply air to the trailer air tanks in a combination vehicle, you must
16. The standard following distance behind other vehicles is at least
17. The air leakage rate for a combination vehicle (engine off, brake off) should be less than ___________________ psi per minute
18. When lowering the landing gear of a loaded trailer,
19. When parking trailers without spring brakes, use ______________________________________ to safely secure the vehicle.
20. Why should the trailer glad hands be locked together or attached to “dead end,” or dummy, couplers when not in use
21. When coupling a tractor to a semitrailer, what should you hook up before backing under the trailer
22. Which of the following is a coupling device used to connect the service and emergency air lines from the truck or tractor to the trailer
23. When coupling with a semitrailer, back the tractor up
24. In combination vehicles, the trailer service brake should be tested with the _____________________________________, but controlled in normal operation with the _____________________________________.
25. When the wheels of a trailer lock up and the trailer begins to swing around ___________________________________ is likely to occur.

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