Here in the Shanghai metro – when trains reach a particular density there is a subtle change in the passenger behaviour as they approach the door – people shift from walking into the train, to backing-in – a conscious effort to avoid being in their personal space and/or avoiding having passengers invade one’s own personal space.

There appear to be cultural and gender variations in how people back-in: for Tokyoites a male backing-into a carriage will often brace one hand against the top of the door to avoid being pushed back out of the carriage, whereas for a female (by local Japanese norms) this would be considered unladylike. In Shanghai I’ve yet to see a steadying arm raised – perhaps because the delineation between surfaces that can be touched and those that one avoids touching is that much starker and perhaps because there aren’t yet engrained practices fro coping with sardine-like crushes.

Where ever you are today – pause your journey, take a seat and observe the ebb and flow of commuter traffic.