Practice Quiz

Commercial Driver's License

Category - Class A

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When connecting doubles, drivers connect the emergency line and charge the trailer air tank. This causes what to happen?
  1. Automatically sets the trailer’s emergency brakes
  2. Automatically sets the tractor's brakes
  3. Automatically sets both the tractor and the trailer’s brakes
  4. None of the above
Explanation
Answer: A - When hooking up doubles, drivers must connect the emergency line and fully charge the trailer air tank in order to automatically set the trailer’s emergency brakes. In addition, it is wise to set wooden blocks behind the wheels of the last trailer to stop it from possibly rolling. Drivers should always inspect their air line connections before trusting them to hold the brakes. This can prevent serious or fatal injuries.
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