Practice question

For the Washington CDL Air Brakes knowledge test, what does the stop-light switch in an air brake system do?

  1. It turns on the brake lights when air pressure is applied to the service brakes
  2. It activates the parking brake automatically
  3. It bleeds the supply tank
  4. It controls the trailer air

Answer: A — It turns on the brake lights when air pressure is applied to the service brakes

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