THE USE OF CHOICE EXPERIMENTS IN THE BUILT ENVIRONMENT: AN INNOVATIVE APPROACH

Choice experimentation is a relatively new non-market valuation technique in which individuals choose their most preferred resource use option from a range of alternatives. At the present time, most choice experiments have attempted to value trade-offs for attributes in the natural environment. This paper highlights the issues raised from using choice experiments to measure combinations of natural and nonnatural attributes in the built environment. This paper also introduces the concept of using computer visualisation techniques to allow the number of attributes in choice experiments to be increased. Computers should allow photographic images to be created, providing participants with realistic and practical views of the changes which can be made to attributes. As these images will replace text descriptions, the cognitive burden placed on participants should be greatly reduced. This means that the number of attributes presented in the images may be larger than in previous studies. Using computer generated images to conduct choice experiments is innovative and quite unique. It is predicted that computer visualisation techniques will enable participants to gain a better understanding of what they are being asked to value which in turn will make the results more meaningful. Computer visualisation techniques have the ability to make choice experiments more user friendly than they have been traditionally. Introduction The purpose of this paper is to present an introduction to work being undertaken at the Robert Gordon University in Scotland. The aim of the project is to develop a methodology that can be used to value combinations of attributes (both natural and non-natural) in the built environment. The research takes on an interdisciplinary approach, combining concepts from environmental economics, environmental psychology, urban planning and environmental design. This project will identify and value optimum combinations of both natural and non-natural attributes. As both use and non-use benefits are derived from well designed streetscapes, it is appropriate to measure those benefits using a non-market valuation technique. Choice experimentation is a technique capable of estimating both use and non-use values. Choice experimentation is a non-market valuation technique in which individuals choose their most preferred resource use option from a range of alternatives. Blamey et al. (1997) describe the technique as one in which individuals are typically presented with six to ten ‘choice sets’, each containing a base option and several alternatives, and asked to indicate their preferred option in each set. The base option generally corresponds to the current situation or a ‘do nothing’ option, which remains constant across all the choice sets. The attributes in each of the remaining choice sets are then varied, allowing the researcher to estimate the relative importance of each attribute. Choice experiments attempt to identify the utility that individuals derive from attributes of the commodity being valued. By examining the trade-offs individuals make when making choice decisions, researchers can infer four pieces of information from choice experiments (Hanley et al. 1998): • which attributes significantly influence choice; • the implied ranking of these attributes; • the marginal willingness to pay (WTP) for an increase in any significant attributes; • the implied WTP for a program which changes more than one attribute simultaneously. 1 Streetscapes are described as city passageways, including streets, boulevards and alleyways. They encompass public spaces such as roadways and footpaths, semi-private spaces such as residential front gardens and commercial terraces, and include attributes such street trees, flower-boxes, etc. which enhance these spaces (City & County of San Francisco 1997). The work to be carried out in this project will essentially challenge the existing choice experiment methodology. Most choice experiments have only four or five attributes in a choice set, but such a number is inadequate to realistically describe the urban environment. A more holistic approach to environmental valuation will be taken; not only through the use of a large number of attributes, but also through an analysis of the context. This means that the physical and spatial characteristics which should be regarded as significant, and any apparent relationships between them, will be identified. A major methodological challenge in using choice experimentation is selecting an underlying factorial design that can accommodate the many attributes that are found in the urban environment. Generally there is a trade-off between the number of attributes tested and complexity when deciding on how many attributes to include in the choice set (Blamey et al. 1997). As the number of attributes in the experiment increases, the number of possible choice options increase at an exponential rate. In turn, the experimental design becomes more complicated and the cognitive demands associated with evaluating the choice sets increase. Ironically, choice experiments are used to derive economic values for individual attributes and the packages of which they are part. Therefore identifying and defining all the relevant attributes is important (Batsell & Louviere 1991). The project will investigate ways in which larger numbers of attributes can be included in the choice experiments without increasing the cognitive burden on the survey respondents.