Analysis of Spatio-temporal Stability in Accessibility

A Case Study of Ophthalmic Hospitals in Matsudo City, Chiba Prefecture

Abstract

This paper analyzes the stability of accessibility to ophthalmic hospitals in Matsudo City, Chiba Prefecture, by changing measurement methods and aspects using geographic information systems. Especially the number of spatial choice and area unit are changed, and consulting hour is considered to analyze the stability of accessibility.
First the accessibility is measured as the shortest road distance from the center of a neighborhood districts (Chouchou-aza) to the nearest hospital on the road network. The accessibility to ophthalmic hospitals in Matsudo is classified into four levels: good, normal, bad, and very bad. This accessibility is compared with the accessibility classified into nine types of four levels in terms of the shortest road distances from Chouchou-aza not only to the nearest but also the second nearest hospitals. The reason why the second nearest is considered is that a second choice is important in the spatial choice of an urban facility. The results of comparison are as follows.
(1) Most of Chouchou-aza evaluated as having a high level of accessibility to the nearest facility are lowered by considering the second nearest one. This means weakness of their stabilities. On the other hand, the Chouchou-aza at the bad and very bad levels are stable at the same levels even if considering the second nearest. It is noteworthy in changing the method of measurement that about 80% of Chouchou-aza evaluated as good are weak in stability.
(2) In Chouchou-aza with good accessibility where the agglomeration of facilities is low, stability is weak. Therefore the second nearest facility should be considered in the measurement of accessibility.
Next the accessibility is classified into nine types in terms of the shortest road distances from the center of a 100-meter mesh to the nearest and second nearest hospitals and is compared with the accessibility at Chouchou-aza level.
(3) In 20% of Chouchou-aza, the accessibility differs in half the area in comparison with the 100-meter mesh level.
(4) A modifiable unit area problem in the measurement of accessibility will occur in the city center where the evaluation of accessibility drops when changing the unit area of measurement from Chouchou-aza to 100-meter mesh.
Finally, accessibility is measured by considering consulting days and hours to understand the temporal dimension of accessibility.
(5) All hospitals are not open at the same time, but the accessibility is nearly same as at 10 a.m. on Monday.
(6) Saturday is the lowest provision level in hospital service except for Sundays and holidays. The number of hospitals opened is the highest at 3 p.m. on Saturday and accessibility around the largest center of Matsudo is highly stable, but the second and third largest centers are unstable with accessibility falling drastically.
This paper analyzes the stability of accessibility by changing measurement methods and considering time the dimension. It was clarified in this paper that the stability of accessibility is dependent on the location pattern and density of urban facilities.