The main argument of this thesis is that the social impacts of new developments are socially constructed. Rather than simply being affected by impacts local people are active in constructing them. The thesis begins by providing an overview of the literature on social impacts and their assessment, before moving on to outline what is meant by social constructionism and some of the major debates about the approach. The application of a social constructionist approach to environmental issues has been criticised by sociologists adopting a more realist stance, on the grounds that it ignores the reality of environmental problems and has little practical use. This realist critique is shown to be mistaken in several ways. Two case studies were conducted to explore how social impacts are socially constructed. Both focus on the impacts of roads; one study was of an area where a new road was proposed and the other where a road had been recently constructed. In both case studies a variety of data were collected. These data are analyzed to illustrate aspects of local people's construction of the impacts of the road. Analysis explores issues such as why any protest about impacts emerged and why it focused on particular issues. The rhetorical strategies employed to construct impacts as real and serious are also examined. Particular attention is paid to the role of identity in the construction of impacts. Participants are shown to work to characterise themselves as ordinary people, as local people and as different from the 'experts' in order to make robust claims about impact.