Using Geometry to Evaluate Strategic Road Proposals in Orbital-Radial Cities

Abstract

This paper uses geometry to evaluate major road proposals in cities with road networks consisting of orbital and radial routes. The type of geometry used is a development of the Karlsruhe or Moscow metric after the cities where it was identified, although the results have wider applicability. The paper begins with a detailed consideration of the relationship between route speeds, junction access and service areas. New urban patterns are presented using optimal space-filling techniques in which the aim is to maximise drive-time coverage with the minimum number of junctions. The method is then refined to allow for effects such as congestion and interstitial access. The results are then used in a case study to evaluate a well-known strategic road plan for London first proposed in the 1940s. There follows a general discussion about the policy and planning implications for London and further possible developments of the techniques presented.