the rubber-tyred motor vehicle heralded the advent of the automobile-dependent city, with densities of ten to twenty persons per hectare (twenty-five to fifty per acre). The automobile freed people from the tracks, widened the choice of residential location urban cores. As Figure 28.1 shows, many cities comprise a small walking city centre and a distinctive transit city with higher density and very different transport patterns, surrounded by an antomobile-dependent city with uniformly low-density suburbs and high car use.