After my trip to New York, I've been thinking that there needs to be a driving version of the Sapir-Whorf Hypothesis. The way you drive changes the way you think. Or to put it a snappier more quotable version for all the link-texts, "As go the drivers, so go the pedestrians." New Yorkers (at least the ones I saw) have a very aggressive driving style, pushing their cars in wherever there's an opening, but at the same time they respect the traffic signals. I noticed that the pedestrians acted much the same way: walk quickly without acknowledging the people around them, no pushing but no patience for people standing around gawking -- and surprisingly little jaywalking, really only doing so when they know from experience that the light is about to change or when there's no crosswalk nearby. But when they expect to be able to walk, they walk with perfect confidence. Pushy, pragmatic, but in their own way polite.
Compare that behavior to the drivers here in New Hampshire, and you see a kind of wishful timidity: people generally obey the speed limits (well, add 10 mph to the posted limit, and people obey that number pretty faithfully) but they'll gladly speed up when a Beemer comes along even faster to act as a lightning rod for police irritation. Drivers here tend to be abundantly cautious, to the point of stopping at yellow lights, or slowing down just in case that pedestrian might be thinking about crossing the street. You'd expect that sort of thing in an area where the pedestrians are kamikaze jaywalkers, but the folks on foot are often just as timid as the drivers, waiting far too long before taking that second step into the crosswalk, waiting patiently for the walk sign on a street with no cars, etc.
In other words, if there were not some shared element going on, I would expect the NYC driving environment to produce NH-style timid pedestrians, and the NH drivers to produce NYC-style pedestrians. And at least in the latter case, it does: but only in a college town like Hanover where the pedestrians are usually not also drivers!
I'd extend this example to Boston, but I think there's a highly promising paper to be written on that one, maybe for a journal of abnormal psychology...