| To release oil and water buildup | |
| To check for leaks | |
| So they can be inspected | |
| To verify they meet pressure requirements |
| Can be used indefinitely | |
| Can still be used several times | |
| Immediately fail | |
| Cannot be used |
| Two sets of brake controls operate a single brake system | |
| Two brake systems that each have their own set of controls | |
| Two brake systems use the same set of brake controls | |
| Two control systems that each have their own set of breaks |