What is the purpose of the trailer handbrake?

The purpose of the trailer handbrake is specifically to keep the trailer stationary when parked. This handbrake is crucial for ensuring that the trailer remains in place once it has been disconnected from the towing vehicle or when it is parked for any length of time. Engaging the handbrake prevents unwanted movement of the trailer, which could lead to accidents or damage, especially on inclined surfaces.

While other functions, such as assisting with braking when in motion or steering, may be related to the operation of the vehicle, they do not pertain to the primary function of the handbrake. The handbrake's explicit role is to secure the trailer in a stationary position, making it an essential safety feature during parking.