How many full brake applications should a vacuum reserve system permit?

A vacuum reserve system is designed to provide additional braking power when needed. The proper function of this system allows for a certain number of full brake applications before the vacuum is depleted. In the context of this question, the vacuum reserve system should allow for two full brake applications.

This is crucial for safety and vehicle control, especially in emergencies where multiple brake applications might be required in quick succession. The reserve ensures that even if the initial brake application uses up some of the vacuum, there is still enough remaining to allow for a second full application. This design is intended to prevent loss of braking capability in critical situations, ensuring drivers have the necessary stopping power to react appropriately.