Access to diversity: definition and measurement of an elusive concept

In his book, Good City Form, Kevin Lynch considered access to diversity to be an important aspect of city quality. At the local level, the provision of diversity in terms of both land-use and social mix is now a key policy objective. Amongst other things, it is argued that local diversity promotes more sustainable travel patterns by encouraging walking and supporting good public transport connectivity. Variables which attempt to measure diversity have been included as explanatory variables in a number of studies of travel behaviour and evidence in support of these arguments has been found. However, the variables used are, on the whole, based on small-area attributes, (arguably) offer a limited interpretation of diversity and take no account of the diversity of the wider city context. This paper draws on the extensive literature which exists on the definition, measurement and valuation of diversity in fields ranging from economics to ecology to develop quantitative measures of access to diversity. These measures are consistent with and can be employed alongside commonly used measures of accessibility, such as cumulative opportunity and gravity model measures, which provide an assessment of the quantity of access afforded by the city. The application of these measures is illustrated using data from the Glasgow urban area. The relevance of this work to the practice of Accessibility Planning is also considered.