This made me laugh. It is also true on public transport in China. The older people have really figured out this hierarchy and it is funny to watch them eyeing improved seating positions as a stop approaches. Then, the doors open, seats vacate and there is a rush of senior citizens trying to improve their position however marginally. Quite funny to watch once you realize what is going on (also a good way for the inexperienced to quickly find out which seats are best).