ABSTRACT
When different configurations of population or employment and resultant activity distributions are assessed relative to one another, some measures of accessibility have traditionally been used in a total benefit criterion (Wilson et al. 1981). Especially, in geography accessibility has long been interested in as a fundamental component of the discipline and to some extent as an indicator. Since the seminal work of Reilly (1931), the most common practice has been to relate the concept of accessibility to the basic gravity model or the broader family of spatial interaction models (Wilson 1971). The basic law of gravity model is that movements between two sites are proportional to the products of their characteristics and inversely proportional to a power of the distance separating them. One of the well-known measures of accessibility is a gravity-like formula by Hansen (1959). A number of modified versions of the Hansen-type framework have been proposed so far (for example, Isard 1960; Ingram 1971; Wilson 1967, 1974), however, a more rigorous discussion on the reason why we have to assume a continuous and a decreasing properties of distance function has not been made in the contexts of accessibility. In fact, It is known that the concept of transportation costs generally includes a noncontinuous property (Baumol et al. 1988).
