Abstract
This work addresses the behavior and cognitive problems associated with stated preference surveys, more specifically respondents' disengagement. The paper provides an extensive introduction and literature review, and the analysis of the extent of the respondents' disengagement observed in a high-speed railway survey conducted in Portugal. The results show a high level of disengaged respondents, especially for the car users; evidence of learning rather than survey fatigue as a respondent progress through the questions, and connection of disengagement and social-economic characteristics of a person. The findings suggest that disengagement has an important impact on the travel demand modeling results. Finally, the study analyzes possible reasons of disengagement and suggests possible future solutions to the issue. The paper aims at helping to improve the conduct and usage of data in the future.