Only public transportation vehicles are permitted to pass the signpost on its left

What is the meaning of the following road sign (the yellow colored left arrow)?

1. It is permitted to drive to the right of the yellow line on the road.
2. Follow the direction of the yellow arrow only.
3. Public transportation vehicles are prohibited to pass the signpost on its left.
4. Correct answer: Only public transportation vehicles are permitted to pass the signpost on its left.