Practice question

On the Michigan CDL Air Brakes test, what is the function of the relay valve in trailer air brake systems?

It speeds up the application and release of air to the trailer brake chambers because the chambers are far from the foot valve
It cools the brake drums
It dries the air
It applies the parking brakes

Answer: A — It speeds up the application and release of air to the trailer brake chambers because the chambers are far from the foot valve

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