What is the primary purpose of a parking brake system?

The primary purpose of a parking brake system is to hold and maintain the vehicle in a stationary position. This braking system is designed to prevent the vehicle from rolling when parked, especially on inclines or slopes. Unlike the regular braking system, which is used for stopping the vehicle during operation, the parking brake provides a reliable means of securing the vehicle when it is not in motion.

In this context, while the other options involve braking in some manner, they do not align with the primary function of a parking brake. For instance, assisting in normal braking or applying additional pressure to the main brakes refers to functions that are primarily active during driving conditions, not while a vehicle is parked. Enhancing traction during acceleration relates to dynamic vehicle control rather than maintaining a stationary position. Therefore, the parking brake is specifically engineered for securing the vehicle, making the correct answer about its purpose clear.