The Traffic Flows on Japanese National Motorways

Abstract

The theme of this paper is to analyze the O-D matrices derived from the survey on national motorways under the Japan Highway Public Corporation's management in 1990 and to describe spatial structure of traffic flows on motorways in Japan.From the period of rapid economic growth in 1960s to date, Japanese government has constructed motorways all over the country on the basis of efficiency.The largest outward flow from each prefecture or interchange in analyzed to elucidate the pattern of traffic flows. As for the flows among prefectures, the main flows are concentrated in the cities, for example, Sendai, Tokyo, Nagoya, Kanazawa, Osaka, Hiroshima and Fukuoka, which function as the center of a regional block consisting of several prefectures. Meanwhile, the flows among interchanges are apt to be contained within each prefecture and to concentrate in the interchange which is located near the seat of prefectural government.Especially, on the motorways connecting Tokyo, Nagoya, Osaka and Fukuoka large metropolitan areas, there is a lot of traffic for freight transportation, thus the traffic decreases on holidays. While on the other motorways, such as Tohoku, Hokuriku and Kyusyu, the traffic volume for leisure and recreation purpose is larger than for freight transporatation. Therefore, the traffic increases on holidays.Lastly, the flows of each kind of freights, passengers and drivers among 14 major regional blocks (See Fig. 7) are analyzed employing multidimensional scaling. The data of O-D matrices are converted to dissimilarity data to divide total traffic volume by each cell. The author identifies the following flow patterns from each plot of scores (See Fig. 8).1. The largest three metropolitan areas, Tokyo, Nagoya and Osaka are closely connected.2. The main flow patterns are divided into Eastern and Western parts of Japan.3. The blocks adjacent to the largest three metropolitan areas show close connectivity to each metropolitan area.The analysis reveals that the traffic on Japanese motorways is highly concentrated in large metropolitan areas. The expansion of their network has not fully contributed to alleviation of congestion and over-accumulation of industries and urban functions.