eli5 Why do trucks and busses do the “tsshhh” thing when they stop?

Question

eli5 Why do trucks and busses do the “tsshhh” thing when they stop?

In: Engineering

Answer 1

They have what are called air brakes. Traditional cars use hydraulic brakes, but with larger vehicles, the are more dependent on a pressurized air system. The hiss you hear is the release of pressure.

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