Mixed Method Data Collection in Travel Surveys: Challenges and Opportunities

Abstract

The Transport and Population Data Centre (TPDC) has been running the Sydney Household Travel Survey as a continuous survey since 1997/8. It collects information on day-to-day travel in the Greater Sydney Metropolitan Region. Based on the faceto- face personal interview method, it has been seen internationally as a leading example of achieving high quality results in terms of response rates and accuracy of trip reporting. Using this data collection method, the full response rate and part response rate are currently about 55% and 8% respectively. However, in line with recent trends, this rate has declined significantly over the years since 1981 when it was about 79% and since 1997/98 when it was still around 76%. This paper examines the issue of decreasing response rates and sets out to find if using mixed modes of data collection would produce better trip estimates and would be more cost effective. It begins by addressing the intuitive question (can we get a higher response by sampling more households) and explains why this is the wrong question. The correct question is whether new modes of data collection will achieve better response rates – and more importantly better trip estimates and cost efficiencies. By examining the limited existing evidence from both transport and other resources, the paper is able to show in which cases it is likely that multiple modes might make a difference, and when they might not. However, the paper clearly concludes that without some further information and research, it is not possible to make an informed decision on the usefulness of a multi-modal intervention. The report concludes by describing the parameters of a study that could answer the question of whether and what type of mixed mode surveys would improve trip estimates and cost efficiency of the current Sydney Household Travel Survey.