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The paper describes the development and application of physical-financialmodelling techniques to the analysis of relations between development design –covering the broad characteristics of a scheme, such as land use mix, developmentdensity and built form – and financial viability. It is divided into two parts

related meaningfully to the idiosyncrasies of particular development proposals on individual sites.

It is for these reasons that much attention has been paid to more qualitative, case study research. But this methodology achieves empirical richness at the cost of a restricted evidence base. For example, some of the most quoted studies in the UK are Carmona et al (2001; three pairs of case studies (6)), Savills (2003; four pairs of case studies (8)), Savills (2007; three trinities of case studies (9)) and Amion et al (2007; seven single, outline case studies). In addition, the definition of the value arising from good design is drawn very widely. It includes economic, social and environmental value accruing to a wide range of actors - such as developers, investors, occupiers and the local resident and business communities - over the short, medium and longer term. However, for reasons of market structure, most of these various streams of value are not captured by the developer (Savills, 2003). The developer is primarily interested in exchange value - that is, prices or rents/yields achieved on disposal (Macmillan, 2006; Amion, 2007) - and, secondarily, in the reputational value arising from corporate association with well-designed schemes.

Figure 4: The Optimum Development Density of a Site

If the relation between design and value arising from a particular aspect of the development is examined in more detail, the picture is even less clear. One of the main ways that "good urban design can add value to development [is] through using land highly efficiently" (Roger Evans Associates, 2007, page 110, square brackets added); that is, by increasing the density of development. Figure 4 describes the