The impacts of a sustainability appraisal on transport strategy selection

There is great concern about the long-term ‘sustainability’ of the transport sector both nationally and globally. Much work has focussed on the development of indicator sets to monitor changes in the sustainability of transport over time (Litman, 2005). However, in reviewing indicators for sustainability in 2003 Gudmundsson concluded that “Even a perfect indicator system for sustainable mobility may be of little relevance if it has no bearing on actual decisions taken”. The research described in this paper attempts to answer these concerns by bringing together modelling tools to try and forecast the impacts of a range of transport strategies across the three pillars of sustainability (economy, environment and social). The paper begins by defining key concepts and describing the framework for sustainability appraisal, including how it differs to existing frameworks. The framework was presented to 14 key stakeholders including four central government departments (transport, planning, finance and environment), practitioners and pressure groups. The outcomes of these discussions and modifications made to the proposed framework are presented. A practical implementation of the framework has subsequently been undertaken for a large Metropolitan area in England. Three scenarios examining differing levels of investment in the transport system, degrees of behavioural change and demand management measures are presented. Of particular interest is the attempt to link a strategic land-use transport interaction model to a GIS-based model of accessibility and social deprivation. The findings suggest that there are serious gaps in our capabilities in capturing sustainability impacts under economic, social and environmental headings. Despite this, the process proposed identified some conflicts between the types of scenarios scoring positively under current appraisal methods and those proposed. This suggests the need for a broader consideration of the impacts of strategies, including the long-term direction of change such as that proposed.