What is the purpose of the handbrake or parking brake?

The purpose of the handbrake, also known as the parking brake, is to secure the train when it is stationary. This safety mechanism is vital for preventing unintended movement, especially on grades or during loading and unloading procedures. When a train is parked, the handbrake is engaged to ensure it remains in place, providing a crucial layer of safety for rail operations.

This is distinct from the functions associated with starting the engine, enhancing acceleration, or modifying braking efficiency. Starting the engine is accomplished through other means, while acceleration relates to the train's propulsion systems, and braking efficiency is typically managed through the primary braking system rather than the handbrake. Thus, the function of the handbrake aligns specifically with securing the train in its position when not in motion, making it essential for safe train operation.