According to safe passenger bus operating procedures, what is the mandatory safety rule when arriving at a passenger boarding/alighting station?

1. Open the passenger doors while slowing down from 15 km/h to speed up boarding
2. The bus must come to a complete standstill, with the parking brake applied, before opening the passenger doors (车未停稳，严禁开门)
3. Open the rear door first while continuing to roll toward the curb
4. Instruct passengers to jump off as soon as the bus enters the bus stop bay