A rear-door brake interlock holds the bus stopped on level ground while passengers board. What should the driver remember before leaving the seat or parking on a grade?

1. The interlock is not a parking brake and must not be relied on to secure the bus
2. The interlock legally replaces the parking brake on every bus
3. The interlock lets the driver leave the bus running in gear
4. The interlock works only when the windshield wipers are on