Nonresponse analysis in a longitudinal smartphone-based travel study

Abstract

Currently, travel surveys are the standard method for measuring mobility in official statistics. Nonresponse and measurement are problematic in travel surveys, due to the high burden and non-centrality of the requested information. To overcome these issues, new methods emerge. The aim of this paper is to assess nonresponse in an experimental travel study carried out in the Netherlands. A smartphone application was developed that passively collects GPS coordinates and automatically populates a travel diary, Participants are then asked for additional information, such as travel mode.   In the experiment, respondents from a random sample of the Dutch population participated in a 7-day study that varied how respondents were recruited into the study, and the size and timing of a monetary incentive. We study at what stage of the study respondents choose to participate and dropout, and study nonresponse bias across 13 variables from the Dutch population register in order to understand how selective nonresponse in the different stage of the app-study was. We found that incentive group, age and education were strong predictors of nonresponse. The overall representativity of the study, as expressed in R-indicators and Coefficients of Variation was rather low because of this bias. However, we found the same biases going in opposite directions when we computed R-indicators for an earlier web-based travel-diary study. This implies that in the future, diary studies should focus on methods to successfully combine smartphone apps and diaries through the web or on paper in order to limit nonresponse successfully.