by Ryan Avent Yesterday, New Yorkers enjoyed the first day of the city's Summer Streets program, in which a swath of land in Manhattan is entirely closed to automobiles for six hours. The city will do it again the next two Saturdays and might continue with the program after that if residents like the result. It's a neat idea (one that New York borrowed from other cities), but it's most interesting not as a stepping stone en route to a car free future, but as a lesson about the importance of urban design. In much of America, declaration of a car-free day would primarily lead to a lot of stranded households, trapped miles away from any retail with nary a transit option or bike lane or (possibly) a sidewalk in sight. That's one reason that high gas prices have proven so painful for much of America. Cutting back on driving in a low-density landscape means cutting back on everything one does outside of the home. Over time, many suburban residents may substitute to more efficient automobiles, reducing this pain. But in the short run, families either spend less on other things to make room for gas money, or they don't go out.