Is it obligatory to install a reverse buzzer on a bus?

1. No.
2. Correct answer: Yes, it is obligatory to install a buzzer, which will function automatically when shifting to reverse gear.
3. It is only obligatory for taxis.
4. It is only obligatory for public minibuses.

WhyYes, a bus must have a reverse buzzer that comes on automatically when reverse gear is engaged. Almost nothing behind a bus is visible, so the sound warns people.