Evolving suburbs: measuring US subdivision street patterns over time

Street patterns in the United States have changed through time, evolving from a gridiron pattern to one dominated by culs- de- sac and loops by the 1950s. This change has made cities less convenient for pedestrians and cyclists to traverse. This research uses computational GIS techniques to analyze street pattern characteristics at the subdivision level to determine whether this trend toward disconnected street networks has continued over the past 70 years. Results show that the densities of three- and four- way intersections have increased in recent decades, though connectivity between subdivisions has not. Active transportation users may find their immediate neighbourhood more walkable, but remain unable to commute comfortably using those modes. This research also identifies representative subdivisions from Wake County, North Carolina that best reflect this change toward increased intersection density and smaller blocks. The small numbers of entrances to subdivisions have remained largely unchanged for decades. This is identified as a crucial challenge facing suburban street network design for pedestrians and cyclists. Overall, the differences between subdivision street network design in the 1950s and the 2010s is noticeable.