Final answer:
In the event of a service brake system failure, the emergency brake system, also known as the parking brake system, should be used to stop the vehicle. It acts independently and provides a mechanical means for stopping.
Step-by-step explanation:
If a failure occurs in the service brake system, the system you need to use to stop the vehicle is the emergency brake system, also commonly referred to as the parking brake system. This system operates independently of the service brakes and provides a mechanical means to stop the vehicle when the primary braking system fails. It is important for driver safety to know how to engage the emergency/parking brake in case of a service brake system failure.