Final answer:
The correct answer is C) stay parked without using up service air pressure. When a truck or bus has dual parking control valves, it can use a separate tank to maintain parking brake pressure without depleting the service air pressure.
Step-by-step explanation:
If your truck or bus has dual parking control valves, it means that you can use pressure from a separate tank to stay parked without using up service air pressure. These systems allow the vehicle to remain stationary for extended periods without depleting the air pressure that is used for the service brake system.
The dual system provides redundancy and safety, ensuring that there is always enough pressure available to engage the service brakes when needed. When activated, one valve maintains the air pressure for the parking brakes, while the other can be used to control the pressure for the service brakes, allowing the service brakes to remain fully charged and responsive when the vehicle is back in operation.
Dual parking control valves in a truck or bus allow you to use pressure from a separate tank to release the spring brakes to move a short distance (option B) and stay parked without using up service air pressure (option C). These valves essentially provide an additional source of pressure for the spring brakes, allowing the vehicle to be parked and moved even when the service brake system is not pressurized.