Factors Affecting Interview Duration in Web-Based Travel Surveys

Historically, travel surveys have been conducted face-to-face, by mail, or by phone. With the increasing share of households having access to the Internet, other survey modes have been deployed. This paper focuses on web surveys. Among other advantages, using the web to conduct surveys reduces costs and helps mitigate poor response rates among young households. Very few studies have been conducted on interview duration and its determinant using paradata from web travel surveys. Such knowledge is necessary to validate the context in which travel data are gathered and can be used to understand sample and data quality. Interview duration modeling is also essential for allocating survey servers and monitoring interviews during the data collection phase. This paper models interview duration using paradata from nine web surveys conducted in the Quebec province from 2010 to 2014. The main objectives of the model are to assist the monitoring of interviews by detecting outliers, provide a better estimate of the interview duration to respondents and survey managers during the interview, and allow a more precise evaluation of the server performance needed before conducting web travel surveys. Using a multiple regression model, we observed that the most important variables in explaining interview duration were number of car and transit trips as well as number of unique places visited during a day. Conducting the interview on a small-screen device also increased interview duration. The model also provides a baseline estimate of interview duration on the basis of demographic features and questionnaire design.