What type of brake system is primarily used for stopping a vehicle?

The service brake system is designed specifically for stopping a vehicle during normal operation. This system allows the driver to control the vehicle's speed and bring it to a stop safely under various driving conditions. It includes components such as the brake pedal, master cylinder, brake lines, and braking mechanisms (like disc or drum brakes) that engage when the driver applies pressure to the brake pedal.

The service brake system is integral to a vehicle's operation, as it engages during regular driving to slow down or stop the vehicle as needed. It is a crucial safety feature that ensures the vehicle can respond effectively to the driver’s commands, allowing for smooth and safe maneuvering in traffic or while navigating different terrains.

Other brake systems, while also important, serve different purposes. The emergency stopping system is typically activated in urgent situations where the normal service brakes may fail. The parking brake system is used to keep the vehicle stationary when parked, and the backup brake system may function in a limited capacity for additional safety but is not the primary system used during regular driving. Hence, the service brake system is the correct answer as it is the main method for stopping a vehicle during typical operation.