Final answer:
The trailer hand valve is known as the parking brake, which is a specific control for applying brakes on a trailer independently from the truck's brakes.
Step-by-step explanation:
The trailer hand valve is also known as the parking brake. It is a control found in commercial vehicles equipped with air brakes. The trailer hand valve works independently of the regular brake controls and is specifically used to apply the brakes on the trailer only.
This is important for situations where a driver may need to adjust the trailer's brake pressure, such as when parking on an incline or to prevent a trailer from rolling.
This valve is sometimes colloquially referred to as the "trolley valve" or "tractor brake" but should not be confused with the brake pedal, clutch pedal, or accelerator pedal.
The trailer hand valve is also known as the Parking Brake. It is a device used in commercial vehicles to control the trailer brakes independently from the tractor. When the parking brake is engaged, it locks the trailer wheels and prevents the vehicle from moving.