What is the function of the parking brake?

The primary function of the parking brake, also known as the handbrake or emergency brake, is to keep the vehicle stationary when it is parked. This safety feature is especially important to prevent the vehicle from rolling away, particularly on inclines or declines. Engaging the parking brake ensures that even if the regular brakes fail or if the vehicle is inadvertently left in gear, the parking brake will hold the car in place.

While the other options touch on aspects of vehicle braking and control, they do not accurately represent the specific role of the parking brake. For instance, slowing down the vehicle is typically the responsibility of the regular braking system, which is designed for that purpose. Assisting in driving down steep grades might involve the use of engine braking or lower gear ratios rather than relying on the parking brake, which is not intended for active driving. Lastly, increasing brake fluid pressure does not pertain to the parking brake's function, as it operates through a separate mechanism that does not influence the standard hydraulic brake system. By understanding this, it becomes clear that the role of the parking brake is crucial for securing a vehicle when parked, ensuring safety on various terrains.