What does it mean when a yellow arrow pointing straight ahead is marked on the road?

1. All vehicles are permitted to drive straight, but right-of-way should be given to buses.
2. Every vehicle carrying at least six passengers is permitted to continue straight forward.
3. Correct answer: Only public vehicles are permitted to continue driving straight ahead at the coming intersection.
4. Private vehicles are permitted to carefully drive straight.

WhyA yellow arrow on the road is for public transport only. So only public vehicles may go straight along it at the coming intersection.