What is the purpose of the towing unit?

The towing unit is an essential component in a train system, primarily responsible for reading brake pipe pressure and applying or releasing brakes based on the pressure levels detected. This function is critical for ensuring the safe operation of the train, as it allows for the appropriate management of braking actions which are vital during various operating conditions, such as starting, stopping, or coasting.

The ability to monitor and respond to brake pipe pressure directly impacts the control over the train’s speed and stability, making the towing unit integral to the overall braking system's functionality. This ensures that the train remains responsive to the actions of the engineers while also adhering to safety protocols.

While other options may involve aspects of train function, they do not encapsulate the primary role of the towing unit, which specifically focuses on brake management through pressure readings and subsequent brake actuation.