20: Stated Preference Surveys: Do We Have Confidence Tests of the Results?

The use of Stated Preference methods has become increasingly popular within transport research. They have enabled a much more detailed analysis of the evaluation by passengers of different attributes associated with different transport modes. At the same time, they raise the question whether respondents can cope with a complicated hypothetical choice situation. A number of tests for Stated Preference surveys have been developed, but these have only been standardised to a limited extent.

It is important to examine critically the results of surveys based on hypothetical choices. First, is it difficult for respondents to make realistic choices? The exercise can be too demanding and complicated for respondents if we increase the complexity of the design. This can influence the respondent's evaluation of options during the survey and may lead to a simplified or random response. One example is lexicographic answers, investigated in depth by Widlert (1994).