In this image we see a "Superblock" and adjoining cul-de-sac units from the Greenhills development. The Superblock was devised for the Radburn, New Jersey project in the late 1920s. With this concept, all housing faces inward, and surrounds a central greenspace.
Drawing from Library of Congress
Originally, all pedestrian and vehicular traffic in the green suburbs was to be separated. This would be done using paved foot paths and pedestrian underpasses at major roadway intersections. However, building budgets tightened with various cost overruns. A system of pedestrian underpasses was only built in Greenbelt. The Greenhills and Greendale projects had to settle for guarded crosswalks along their foot path networks.
Photo from Library of Congress / Arthur Rothstein