The impact of choice inconsistencies on the valuation of travel time in stated choice studies

A new test procedure revealing choices that are jointly inconsistent has been developed and applied to the respondents’ choices in the Norwegian value of time study (Ramjerdi et al. 1997) and a study providing the Norwegian road authorities with valuation of environmental benefits for use in Cost-Benefit Analysis (Sælensminde and Hammer 1993). Our analysis show that lexicographic and inconsistent choices commonly occur in several stated choice tasks and have a significant impact on the valuation of reduced travel time. Both people’s difficulties handling the choice tasks and real preferences cause lexicographic choices. Different abilities to choose are also an important explanation of inconsistent choices. The occurrence of inconsistent choices is shown to be largest first in the choice sequence and is reduced for later choices. These results suggest that the respondents may need more training and help to choose consistent in stated choice studies. Acknowledgements: This paper was written when the author was visiting researcher at Institute of Transport Studies, University of Sydney, from October 97 to April 98. I am grateful to Ronny Klæboe, Ståle Navrud and Farideh Ramjerdi for valuable comments on previous versions of this paper. Thanks also to Jan-Erik Lindjord for his excellent programming and comments, and to David Hensher for his hospitality. The study is financed by the Research Council of Norway and the Institute of Transport Economics in Oslo.