Regional urban systems in Japan have a close relationship with prefectural territories which have continued without any changes since the proclamation of the prefectural system in 1890. The intra-prefectural administration and regional development policies of prefectural governments have affected the development of regional urban systems. The population of prefectural capitals has gradually been controlled by the population scale of the prefecture. Analyzing the migration flows among 649 cities in 1980, a city usually has a close connection to other cities within its own prefecture and forms a regional urban system with the hierarchical structure in which a prefectural capital is set up at the top. The hierarchical structure of the regional urban system in each prefecture mostly reflects features of its starting point, although regional differences between core and periphery areas have appeared in the process of urban growth.
As shown in Figure 2 and Table 2 each regional urban system with hierarchical structure is classified into five groups: uni-center type, bi-polar type, split urban system type and metropolitan city type. In addition, the type dependent on a metropolitan city has gradually grown in the vicinity of a metropolitan center according to the developing urban system of a metropolitan city type. Moreover, it can be divided into early, intermediate and late stages due to the process of dependence. Figure 3 represents typical cases of each type shown in Table 2.
From the point of view of the workers of central functions measured by the number of sale and service workers (Pop. Census 1985), most of cities can be classified into large (over 30, 000 workers), middle-size (7, 000 to 30, 000 workers) and small-size cities (3, 000 to 7, 000 workers). As a result, we can recognize that at least the central part of most prefectures are serviced by large cities of their own or nearby metropolitan cities. Tottori and Shimane prefectures are exceptional cases in which even the inhabitants of prefectural capitals are not supplied with the central services of a higher order.
When we try to delimit the commuting area of a city by a commuting rate of more than five percent of workers and regard the commuting area as the city region in which inhabitants can enjoy central services of its city level, each prefectural territory is divided into four city regions: large, middle-size and small-size cities and the outlying area. Then, counting the rate of population involved in the city region of each level and classifying a prefecture by the dominance grade of the population rate, five types can be obtained as in Table 4 (vertical): standard type, metropolitan type, middle-size city type, small-size city type and outlying area type. While metropolitan prefectures or the prefectures near to them such as Saitama, Tokyo, Kanagawa, Aichi, Kyoto, Osaka, Hyogo, Nara and Chiba belong to the metropolitan type and the like, Hokkaido, Ibaragi, Tokushima, Kochi, Nagasaki and Kagoshima belong to the outlying area type. In comparison to the connection structure of regional urban systems in Table 2, it is difficult to clearly classify their spatial pattern. Although the spatial pattern of city regions can be classified into four levels by considering their development process (Table 4, across), there are several cases difficult to classify because of the areal differences of city regions within a prefecture. While such a spatial pattern is to some extent related to the types classified by the population rate of each level of city regions, it does not correspond to the hierarchical pattern of connection structure and it is difficult to explain the relation between the spatial and connection types.
Cities are also classified into four types according to the relation to their city regions: standard type, half-dependent type, independent type city (Selbstversorgerort) and satellite city type.
