The driver is not allowed to open the door anywhere but at a bus stop, the company running the bus forbids it. Quite strictly, actually. I think it is mainly because of insurance things. It is the same in a traffic jam when you are on the bus and the next bus stop is just a few meters away, and the bus is stuck and nothing moves -- impatient people will get angry because they want to leave the bus, but the driver is just not allowed to open the door except when the bus has properly reached the next bus stop.

Some bus drivers do open the door on some such occasion, but they can really get into trouble if they are caught doing that.