In Ho Chi Minh City (and probably Vietnam in general but not 100% sure). Our commercial district is very concentrated.

The busses in general are some form of public-private partnership. Several private bus companies operate the city busses. There are some annoying edge cases. For example, pre-purchased tickets are a mess -- better pay cash. If another operator takes over your route, even temporarily, your tickets can't be used.

Mostly it seems to work though, I take the bus fairly regularly and it's quite nice. It's clean, has OK air conditioning, and arrives frequently enough that I don't have to check the schedule. There's someone to help elderly people and children on and off the bus. Elderly people ride free, reduced price for students, etc. It's pleasant.

Some of these busses are mini-versions for less popular routes. I think I've even seen a couple of other vehicle types, like some form of van (rarely). One or twice a sort of truck with benches.