A transit bus has a brake-door interlock. The driver stops on a hill, opens the rear door, and plans to rely on the interlock instead of setting the parking brake. What is wrong with this plan?

1. NY CDL-10 says a brake-door interlock must never be used in place of the parking brake
2. Interlocks are designed to increase throttle on hills
3. Interlocks make passenger doors emergency exits only
4. The parking brake is prohibited on transit buses