This is a snippet from a NYT article titled Friends of a Certain Age, by Alex Williams:
As external conditions change, it becomes tougher to meet the three conditions that sociologists since the 1950s have considered crucial to making close friends: proximity; repeated, unplanned interactions; and a setting that encourages people to let their guard down and confide in each other, said Rebecca G. Adams, a professor of sociology and gerontology at the University of North Carolina at Greensboro. This is why so many people meet their lifelong friends in college, she added.
There’re lots of situations that might lead to fulfilling the three conditions for close friendship formation. But one thing I’ve noticed about living in a small town, where most errands and trips are done on foot, is that walking tends to help.
I think the walking part is more important than the size of the town. I’ve lived in small communities where there was more driving than walking and close friendships were harder to form.
Walking is probably a big part of people forming their lifelong friends during college (at least in the US). College students walk around more and usually don’t have a car yet either.
We derive a big part of our happiness from close bonds with other people and walking more seems to increase the likelihood of forming new friendships. Friendship is another reason to walk more.