Who drops off web-based travel surveys? Investigating the impact of respondents dropping out of travel diaries during online travel surveys

Household travel surveys collect core datasets for modelling passenger travel demand. However, the decline in survey completion rate has become a concern in recent years. Among all components, the travel diaries are the most challenging part of CAWI travel surveys and suffer significant dropouts of participation. Therefore, an investigation is necessary to understand the influential factors contributing to participation dropouts while reporting their travel dairies and subsequent non-response bias on data quality. This study utilizes binary logit models to capture the relationship between respondents’ drop-off behaviours while filling out travel diaries, their socioeconomic characteristics and different travel diary designs. The study also develops a generalizable analysis framework to measure the impact of non-response bias on data quality. The analysis framework incorporates a trip generation model with microsimulation and bootstrapping techniques. The results show that a diary design with stable repetitions is preferred by respondents and results in less non-response bias in the final dataset. This study also proposes recommendations for future travel surveys.