A spatial framework for environmental impact assessment and route optimisation

This paper describes a geographical information system (GIS)-based prediction and quantification framework for the environmental impact assessment (EIA) of road schemes. The key feature of the framework is that it accounts for the spatial variability of environmental components and potential impacts. Spatial impact functions, embedded within a GIS, have been developed for the prediction of road noise, air quality, visual impact and direct loss. A quantitative cumulative impact score is derived for each alternative option through the application of weightings to the predicted impacts, thus enabling alternatives to be compared rapidly and objectively. The framework incorporates a route optimisation tool based on Monte-Carlo simulation. The sensitivity of the apparent ‘best’ option to the allocation of impact weightings has been explored. The application of the framework is illustrated using two case studies—the A50 (A564) Doveridge Bypass and the A69 Haltwhistle Bypass. A discussion on the relevance of the methodology in the context of current UK procedures for road EIA is presented.