THIS summer the city’s Department of Transportation inaugurates a new bike-share program. People who live and work in New York will be able to travel quickly and cheaply between many neighborhoods. This is major. It will make New Yorkers rethink their city and rewrite the mental maps we use to decide what is convenient, what is possible. Parks, restaurants and friends who once seemed beyond plausible commuting distance on public transportation will seem a lot closer. The possibilities aren’t limitless, but the change will be pretty impressive.