When the pioneering urban sociologist William Whyte studied the movement of pedestrians in cities, David Epstein explains (in Inside the Box), he found that elements of public spaces that accommodated the very young, the very old, and people with disabilities led everyone to use a space more:
Through the 1970s and ’80s, Whyte persuaded New York City officials to alter public spaces to include ramps, flexible seating, shaded areas, numerous entrances, clear sight lines, and to be no more than a few feet above or below street level. “There must be access for the disabled,” he said. “In effect, better access for everyone.” His guidelines rejuvenated spaces like Manhattan’s Bryant Park, which transformed from an invisible-from-the-street haven for drug dealing into one of the busiest public spaces in the world, integrated with the surrounding streets in a seamless river of urban life.
I’ve mentioned Whyte’s The Social Life of Small Urban Spaces before. The video is worth watching: