Retail impact assessments: evaluating two competing models

Hamzah Khawaldah & Mark Birkin & Graham Clarke, "A review of two alternative retail impact assessment techniques: the case of Silverburn in Scotland," The Town Planning Review 83 (2012): 2

The take-away: Upon evaluating the merits of two retail impact assessment techniques—namely “the traditional RIA step-by-step methodology and a disaggregated spatial interaction model (SIM)—this article finds the traditional RIA to feature significant flaws that make SIM the preferable technique. For the authors, SIM models “are much better at representing the mutual interactions between competing centres across a whole range of spatial scales.” 

Abstract: Retail impact assessment (RIA) is a common methodology employed by local authorities in the UK to determine the impacts of new shopping centre developments on existing town and city centres. In the UK, initial approaches utilised retail modelling techniques such as retail gravity models, the most notable example being the Haydock study in 1964. There was widespread opposition to increasing quantification in planning and the use of mathematical models in the late 1960s and early 1970s, as model assumptions were increasingly questioned and different agencies brought different model results to the enquiries. In the 1980s the Department of the Environment advised against the use of mathematical models in impact studies. However, RIA has continued since the 1980s using alternative but still largely quantitative approaches. The aim of this article is to begin the research task of critically evaluating this standard RIA approach  (widely used by retail consultants for planning enquiries) against traditional mathematical modelling procedures. Using the new Silverburn retail centre in Glasgow, UK, we shall explore the potential impact of the new centre based on these alternative methodologies and draw some conclusions on the relative strengths and weaknesses of each.

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