What is the Johnson bar?

Question

The trailer hand valve, also called the trolley valve or Johnson bar, is used to work the trailer brakes. It should be used only to test the brakes.

Accepted Answer

A hand valve that works the trailer brakes

Answer

A valve that indicates the fuel level

Answer

A valve that measures the amount of liquid in the air brake system

Answer

A valve that allows for the release of excess pressure in the braking system