ABSTRACT
Buchanan's ideas have been widely adopted, and play a critical role in transport planning today. This is illustrated by the approach to road hierarchy as described in A Policy on the Geometric Design of Highways and Streets. In this conceptualization, all streets fall somewhere along a continuum between mobility-only streets and access-only streets. This view defines the role that the street plays in the network, and forms the theoretical basis for the hierarchy developed, which is now used extensively all over the world. In South Africa, as a case in point for Africa, the interpretation of these ideas can be seen in the still widely used Urban Transport Guidelines Series of road design manuals Committee of Land Transport Officials (COLTO). Buchanan's ideas described in the American Association of State Highway and Transportation Officials (AASHTO) document have been translated into a road hierarchy for practical application in road design in South Africa.
