The spatial organization of accessibility and functional hierarchy at the local, regional and national scales – The case of Israel

Accessibility is a well-known basic term in spatial science and planning and is inherently related to functional aspects of places and geographical systems. Therefore, accessibility analysis is considered to be an important tool for defining and explaining regional divisions, as well as for enhancing spatial planning policy. However, as Batty (2009, p. 192) has indicated there are differences between accessibility potential of places and the actual distribution of performance or activities of people and these differences can vary with changes in scale. However, previous studies have examined functional systems and spatial accessibility with little attention to the association among them across geographical scales. Our study attempts to fill this gap and to explore the emergence of spatial accessibility and how relates to the formation of a functional system. The aim of this study is to achieve a better understanding of how spatial accessibility relates to the formation of functional systems at different spatial scales of national systems. Using the space syntax methodology, spatial accessibility was analyzed for the entire national road network of Israel across different geographic scales – from local culminating in the national scale. The analysis was based on angular segment analyses of the road center-line network. Following this, the correlation between spatial accessibility across scale and functional regions was examined, as defined by employment and commuting flows. Exploration of the relationship resulted in a spatial organization connected to the functional systems in Israel. This shows significant correspondence and exposes transitions between local, regional and national spatio-functional systems, as follows. First, a significant correlation between local (2km radius) accessibility levels of settlements with the number of employees and commuters. Second, the regional (15-20km radius) accessibility is highly correlated to the emergence of the main employment centers. As part of those centers, particularly noticeable is the functional dominance of the four metropolitan areas. Third, the main metropolitan areas are integrated at higher scale (from 30km radius) and form together a core region characterized by high accessibility, with a clear distinction from this outer region characterized by relatively low accessibility. This spatial structure conforms to the center-periphery structure at the national level of Israel. Additionally, the commuting flow patterns reveal that the core region is relatively well connected, especially the Tel Aviv metropolitan area, which is also characterized by dominant accessibility. In contrast, no substantial commuting flows were found within the periphery, as well as between periphery-core as would be expected from the low accessibility of the area. It seems that the core region functions at multiple scales (local-regional-national) while the periphery functions only at a local scale. The national accessibility reflects well the separation between the two spatio-functional systems. These findings indicate a close relationship with functional performance across geographical scales and accessibility potentials. They also reinforce the importance of accessibility analysis as an indicator for defining and explaining the functional organization of the entire road network at the urban, regional and national scales.