Missing and inaccurate information from travel surveys - Pilot results

During the implementation of a major regional household travel survey, known as the Victorian Integrated Survey of Travel and Activity 2007 (VISTA07) in Victoria, Australia, a pilot survey was undertaken using GPS to validate the diary survey results, similar to a number of studies in North America and Europe. The pilot results suggest that, as has been reported in most overseas studies, respondents generally underreport their travel significantly. Further, it is also found that respondents tend to overestimate trip times and underestimate (seriously) the distance of their travel. It is also noted that there are a significant number of respondents whose reporting is quite accurate, whilst a minority report significantly different information from what the GPS measures. However, a result found in this study that has not been reported before is that there is a very significant difference between the accuracy of reports from those asked to carry a GPS and those who were not asked to do so. This result suggests that the levels of underreporting of travel found in previous studies may be underestimated to a greater extent than previously believed particularly when one considers that VISTA07 uses a face-to-face recruitment methodology. It must be noted, however, that this was a pilot survey and that the sample size is too small to generalise the conclusions, which should not be used to scale any VISTA07 results.