28: Trip Rate Analysis in GPS-Enhanced Personal Travel Surveys

Trip item nonresponse is a common and documented nonresponse problem in travel surveys. It refers to the failure to obtain complete travel information from travel survey respondents, either at the trip or trip detail level. Although both types of trip item nonresponse occur with travel surveys, under-reported trips are considered to be the most serious problem of incomplete information, because trip rates and general trip-making behaviour are the focus of travel surveys. In fact, trip-level nonresponse causes more significant problems for travel demand modelling because trip rates are the essential input variable for predicting future demand.

Understanding the reasons behind trip item nonresponse has helped researchers identify methods of identifying and correcting for these omissions. In 1982, Brog identified three reasons for non-reported trips (Brog et al., 1982):