Consider, for instance, the situation of a man living on a long street block, such as West Eighty-eighth Street in Manhattan, between Central Park West and Columbus Avenue. He goes westward along his 800-foot block to reach the stores on Columbus Avenue or take the bus, and he goes eastward to reach the park, take the subway or another bus. He may very well never enter the adjacent blocks on Eighty-seventh Street and Eighty-ninth Street for years.