The Use of Modal Accessibility Gap as an Indicator for Sustainable Transport Development

Transport plays an important role in sustainable development because it uses a lot of energy. In order to plan for sustainable transport development, there is a need to develop indicators for assessing and monitoring transport development. In this paper we develop a sustainable transport development indicator by making use of the concepts of accessibility and geographical information systems. A modal accessibility gap index is proposed, which is calculated by finding the difference between the accessibility indices of public and private transport, which are in turn determined by accessibilities to opportunities such as the number of population, jobs, shops, and schools by public and private transport. Considering energy-efficiency, public transport will achieve sustainable transport more than private transport. A higher accessibility gap may mean more sustainable development. In the present study, the accessibility gap of Hong Kong in 1991 is compared with that in 1996 to examine whether transport development has been more sustainable. We also discuss how to use the accessibility gap indicator to test land-use and transport-development policies and scenarios to determine the more sustainable ones.