In addition to everything else, car-centric development has also just generally made people more antisocial. When you live in an area where the only people you see are your immediate neighbours and get around everywhere by hiding in a faceless metal box while everyone around you does the same, that erodes your sense of community, and in turn your ability to see strangers as other people. When you don't see strangers as people, that perception gets replaced by assumptions, stereotypes, and statistics taken out of context, and that makes them seem a lot scarier and less trustworthy.
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