2016 年 125 巻 4 号 p. 523-544
Recently, governments of some cities have adopted urban policies, based on a compact city concept to facilitate accessibility, mainly for mobility-impaired people among Japan's ageing society. The government of Aomori city has planned a popular compact city model, or a centralized urban physical structure, by controlling the urbanized area of the Mid-city zone (population-incentive zone) in the city master plan established in 1999. The effects of measures for providing accessibility to the central railway station as a representative facility of the city center are analyzed, and the implications for urban policy based on a centralized compact city design in Aomori city are investigated. Accessibility, as represented by time-distance to the central station, is measured based on a road network analysis and timetables of train and bus services. As a result, it is observed at a level where most of the population can reach the facility. The simulations are based on the following measures: 1) supporting migration inside of the Mid-city from the Outer-city forming the suburbs; and 2) improving the frequency of bus transportation in the Toyama housing district, a case-study area in the suburbs. The major findings are as follows.
1) Accessibility to the central station by train is improved with migration and the effects are greater for elderly people. It seems to be useful to strengthen these effects if migration is only into the Inner-city. Although variations in migration measures are found under several conditions, accessibility is finally improved to almost the same level. Therefore, it is important to continue migration support measures, even if the pace is slow.
2) Accessibility to the central station by bus from the Toyama housing district is improved substantially under a situation where the frequency of bus services is increased until five-fold. The effect is also improved for elderly people. Some suburban cores such as large housing districts should be set or maintained at least the short-term aims of urban policy, because the population is already distributed in the suburbs and the level of functions of daily life should be maintained there.
Lastly, it is important that the city master plan refers to the phasing of centralization from the suburbs, especially, about methods and times. If it is considered that the suburban cores continue independently in the process of compact city policy, the government of the city should include the cores in the urban structure and the city master plan should be revised.