A foot brake valve is a type of valve that is used in vehicles such as trucks and buses to control the braking system. The valve is operated by the driver's foot and is typically located on the floor near the brake pedal.

The foot brake valve is responsible for controlling the air pressure that is sent to the brakes on the vehicle. When the driver presses the brake pedal, the foot brake valve opens and allows air to flow into the brake system. This increases the air pressure and causes the brakes to engage.

The foot brake valve also allows the driver to control the amount of pressure that is applied to the brakes. This can be useful in situations where the vehicle is carrying a heavy load or is on a steep downhill grade, as more pressure may be needed to bring the vehicle to a stop.

Some foot brake valves can also have additional functions such as automatic adjustment of the brake pressure, emergency release, parking brake and others.