Academic journal article
By Khawaldah, Hamzah; Birkin, Mark; Clarke, Graham
The Town Planning Review , Vol. 83, No. 2
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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Spatial interaction models (SIMs) have a long history in geography and related disciplines, especially following Wilson's derivation of the models using entropymaximising techniques (Wilson, 1967; 1974). Since then they have been used successfully in a range of applied settings, especially as retail location and impact assessment models. Birkin et al. (2002; 2010) review the progress made with applied SIMs in retail location planning. However, it is noticeable that this progress and success has been largely confined to applications within the private sector. A key question is what happened to these models for public sector usage, especially in the UK which is the focus of the study presented here.
Breheny (1988) expressed surprise (on behalf of the academic community as a whole) that spatial interaction models re-emerged in the UK for retail site location or impact assessment in the private sector during the early 1980s. Indeed, spatial interaction models are now integral to the site location methodologies used in many UK blue-chip organisations, such as Tesco, Sainsbury's, Boots, Thomas Cook, etc. (Birkin et al., 2002; 2010). Breheny's surprise was because these models had fallen out of fashion in the public sector in the late 1970s. According to Breheny, this was a combination of disenchantment and Government warnings that the use of such models was not appropriate at planning enquiries. In the view of Guy (1991), there was widespread opposition to increasing quantification in planning generally and the use of mathematical models during the 1970s. Norris (1990) even suggested that this was because SIMs involve 'optimistic guesswork' which is 'hidden by the workings of the model' (p. 108). Despite some SIMs continuing to be applied in the public sector, notably the models of the Unit of Retail Planning and Information (Alty, 1979), the step-by-step retail impact assessment (RIA) methodology became more popular. Even though there are many different versions of RIA, all the examples given in the bibliography here follow the same five main steps, which we review later.
The aim of this article is to provide a critical review of the RIA and SIM methodologies. Although critical comments have previously been made regarding both methodologies (England, 2000; Guy, 2007), very few empirical case studies have been presented in the academic literature. In this article, comparative analysis will be undertaken in relation to a major new out-of-town retail development at Silverburn near Glasgow. Silverburn was chosen as it is the most recently opened large out-oftown regional shopping centre in the UK. This allows the case study to be supported by richly specified consumer data from the National Shoppers Survey (NSS) provided by Acxiom Ltd (available since 2005), as well as by a variety of retail directory sources. …