Towards the Sustainable City: The Impact of Land Use – Transport Interactions. The impact of accessibility and environment coefficients in location choice on transport strategy performance.

Abstract

Over the last decade the concept of integrated transport strategies for urban areas and a means of evaluating them have been developed and widely accepted into practice by major studies of cities such as London (May and Gardner, 1990), Birmingham (Wenban-Smith et al, 1990) and Edinburgh (May, Roberts and Mason, 1992). The development of integrated transport strategies (May, 1991) has been based on the identification of synergy between transport policy instruments (May and Roberts, 1995). These concepts led indirectly, particularly through experience in Birmingham, to the introduction by the Department of Transport of the Package Approach for urban transport funding (May, 1994a) and more directly to the development of the Common Appraisal Framework for assessing Package Approach bids (MVA et al, 1994). It is now generally accepted that transport strategies designed to meet the objectives of economic efficiency and sustainability will require a combination of measures to manage the existing infrastructure more effectively, to provide selective enhancements to that infrastructure and to impose appropriate pricing mechanisms on both public and private transport. In a recent study, funded by EPSRC, we have developed a methodology for identifying optimal specifications for such strategies, and have shown that their performance is particularly sensitive to the contribution of pricing measures such as fares and road pricing (May, Bonsall, Bristow and Fowkes, 1995). However, while we are now able to formulate optimal transport strategies, very few studies have been able to demonstrate that transport policy measures alone will achieve a sustainable situation in which fuel consumption and emissions are maintained at or below current levels (May and Roberts, 1995). In most cases, land use changes will need to be co-ordinated with transport measures if sustainability is to be achieved, and recommendations for appropriate land use measures are beginning to emerge (DoE, DoT, 1993; DoE, 1994). An initial assessment of the potential for co-ordinating transport and land use strategies was carried out using the results of the Edinburgh study (Still, 1992), and showed that the preferred transport strategy would be up to 10% more effective in achieving sustainability when combined with a concentrated land use strategy. However, that study assumed no feedback from transport measures to land use effects. Literature reviews and interviews have demonstrated that the impact of transport on land use is perceived as a serious gap in policy understanding. Interviews also revealed that land use-transport models are treated with some scepticism, because there is insufficient understanding of the relationships within them and because the existing models are perceived as unduly complex (Still, 1996). As a result of this lack of understanding, there is a danger that impacts of transport on land use might have counter-productive effects on the land use - transport strategy. For example, road pricing, which may be a key element in a sustainable transport strategy (May, 1994b), may reduce accessibility by private car, and hence lead to outmigration of business, thus producing a less sustainable land use pattern. Conversely it could enhance the city centre environment, and hence encourage certain firms to relocate to the centre. These twin impacts of transport policy on accessibility and on environmental quality are the key elements in predicting the resulting location decisions of individuals and firms, and need to be better understood if sustainable land use - transport strategies are to be developed