I had a strange thought reading that - it reminds me exactly of my every day journey on the train! Either us 'london commuters' (or the british in general) are really Navajo's, or maybe its in comparison to the very friendly and chatty 'look you in the eye' US public culture ? I'm generalising of course but in a general public setting there is a big difference between the US and the UK. As Einstein said "its all relative"

Of course if you get the latter trains back when most people have been out at the bars, people look straight at you and start talking about any old thing.... but then again thats the only time people are likely to try and point at something using their lips