In a built-up area, what obligation do other drivers have when a scheduled public bus (Linienbus) signals its intention to pull out from a marked bus stop?

1. Other drivers have full right-of-way and the bus must wait until the road is completely clear
2. Other drivers must accelerate quickly to pass the bus before it moves into the lane
3. Other drivers must honk their horn to warn the bus driver not to enter
4. Other drivers must enable the bus to merge by reducing speed and stopping if necessary