The way in which Stated Preference (SP) is designed and analysed is based on certain assumptions about how people behave. However, a growing body of research by psychologists and decision researches suggests that these assumptions may be inadequate. For example, it has been shown repeatedly that the same change in a service attribute is valued differently if presented as a gain or a loss, in fact a loss may be valued twice as highly as a gain. The additive compensatory model so often assumed seems to be a poor model of how people actually make choices, since in practice they use a mixture of methods. Furthermore, SP assumes people have full information, in practice they often only seek partial information. This paper only seek partial information. This paper addresses how this research may be used to improve the practice of SP. It begins with a brief review of some of the more significant findings of researchers in non transport disciplines, and considers how this research impacts on the practice of SP in transport, and what changes should be adopted. The recommendations are backed up by practical results from our own fieldwork. Comparative analyses of mode choice SP data are presented to illustrate the effect of differing weights for gains and losses. The way in which presentation of full information affects choices previously made on imperfect knowledge is assessed based on a study in the field in early 1995. (A)
Abstract