Accessibility of spatial networks: Using ArcGIS network analyst and space syntax to investigate accessibility to urban facilities

Abstract

Accessibility is a critical objective in the field of planning, particularly for urban facilities such as education and health services. Among many models and techniques that calculate accessibility, this study focuses on network analyst tool of ArcGIS and space syntax methodology. In the network analysis of ArcGIS, it is possible to calculate service areas for individual urban facilities within given distance/time limits. Space syntax measures on the other hand, help to understand the overall accessibility dynamics of the network. This study aims to associate space syntax based accessibility evaluation and service area measures of ArcGIS in the city of Mersin, Turkey. Mersin is one of the most populated cities of Turkey with more than 1.5 million people. It has a sloping topography which has affected the development of both the road structure and the settlement structure of the city. Apart from the urban centre, there are villages with rural character in mountainous parts of the city that do not have proper access to most urban facilities. Health and education services are of vital importance and access to these facilities is a must for both urban and rural settlements. Therefore, accessibility of these particular facilities within the Mersin Municipal Area is the main focus of this study. In 2015, the Greater Municipality of Mersin initiated the preparation of an urban development plan for Mersin. Urban development plans usually consider accessibility as a means to organize general transportation flows but not as a network issue that would affect individual accessibility of facilities. Therefore, it is important to understand the direction of development in cities before planning them. In order to comprehend development trends and needs of urban facilities, two types of accessibility analyses were carried out in Mersin. Firstly, health and education facilities were assessed using network analysis toolset of ArcGIS, separately for hospitals, school of medicine and small scale health facilities for health services; elementary schools, middle schools and high schools for education services. Secondly, segment based space syntax analysis was executed, in which integration measures were inspected. Comparison and integrated evaluation of results of these two types of analyses are believed to serve to an improved comprehension of the morphological spirit of Mersin. Further analyses on such issues would play a crucial role in planning.