Road Intersections of Tôkyô

Abstract

Tokyo's road pattern represented by the number and type of road intersections reveals its regional structure to a great degree. All the intersections shown on the 1: 10, 000 topographical maps of Tokyo's ku area surveyed and published by the Geographical Survey . Institute, Ministry of Construction, between 1955 and 1958, were counted and classified by the author for each 1 km2 section optionally established for the purpose of making this paper. As of the dates of the publication of these maps, at least 155, 676 intersections are to be found within the ku area of Tokyo, including 6, 573 dead ends and 32, 980 curving or bending roads (L or C shape) (Tab. 1). Of these, three-roads intersections or intersections with three corners (T or Y shape) occupy more than a half, making a sharp contrast to southern Manhattan of New York where some 60% of the intersections are of four corners (X shape). Strictly speaking, the most complex intersection within the ku area is of eight roads or corners as far as the maps employed are concerned. Combination types of intersections were established for each 1 km2 section by taking out the first three most numerous types of intersections and then by combining them in order of frequency of appearance. In doing so, several combination types are recognized as shown in Tab. 3 and Fig. 2. Out of the four major combination types selected, sections with 3-2-4 combination type, i.e., unit sections with prevailing three corners followed by curving or bending roads and four corners in turn, occupy nearly a half within the ku area of Tokyo. This fact shows that the metropolis is well characterized by the dominance of three corners often mixed with meticulously curving or bending roads, most of which are of rural origin or of socalled natural growth. The combination types were then laid out on a Tokyo map in somewhat simplified form, so that their general distribution pattern could be revealed in reference to the process of urbanizatifsn areally considered. By this analysis, for example, southwestern sections of Tokyo developed largely by the Tokyo Kyuko Electric Railway Co. (T. K. K.) and its related real estate enterprises generally show sections of 3-4-2 combination type being thought to be a relatively well aligned street network as well as spotted sections of 4-3-2 combination type as a representative of the modern geometrical layout of streets. This is the actual situation of the area, although topography there is considerably intricate for Tokyo as in the case of the inner sections surrounded by the Yamate loop line. A concentric tonal structure is to be recognized in terms of the density of intersections (Figs. 4 and 5). High-density areas generally surround the Yamate loop line, approximately 8 km in radius from the center of Tokyo. Density becomes lower toward both center and periphery as a whole. These high-density areas, however, are to a considerable degree in accordance with the areas of a high population density. In these areas, surface land.forms are also intricate generally, causing further possible congestion for road traffic, especially for motorization. It is quite natural to see areas of a low intersection density in the peripheral portions of the metropolis, where a character of urban fringe is still to be seen. Newly reclaimed sections along Tokyo Bay primarily used for port and industrial facilities and accomodations also show a low density of intersections. This fact is well explained by the development of larger-scale structures and establishments there. Excluding such low-density areas as urban fringe and port or industrial areas, only one portion of Tokyo is clearly characterized by the existence of a low intersection density, i.e., Marunouchi and Kasumigaseki areas.