It's a local restricted bus system, going around campus. Small, and they only have a few buses, but they make small routes so one shows up every five or ten minutes (depending on which bus route.)
Usually, they're pretty much empty. Once in a while they end up being really full.
Like most buses, they have a front door and a back door.
Here is what I don't understand.
The back door has "EXIT ONLY" written on it and, in fact, the many bus drivers will not let anyone enter through those doors. Why? I don't know. It's a free bus system, so they're not collecting fares. Some bus drivers *will* let people enter that way, especially if the bus is clearly going to be packed.
But many won't.
I don't get it.