one of life's mysteries. In London the saying about London busses "you wait for one and 3 come along at once" really was true, on the rare occasion I had the money to get the bus home from school, the first bus was always full already with school kids so you'd quickly got the bus just behind it, full, then run to the last one which has some space, it often pulled off as nobody was getting on, well they wouldn't as the driver barely waited 7 seconds
was always funny seeing bus inspectors piling onto a bus at a stop to check tickets and those without them desperately trying to get to the middle door quickly to press the emergency button to get out