The survey is managed by DTU Transport on behalf of a group of Danish authorities and organisations. Thus, it was focused on the needs arising from this group:
- A stable, continuous, operational, reliable, easy-to-comprehend survey
- Often very detailed, but generally not very advanced analyses
- Data which cannot be drawn from other sources
The basic aim of Danish national travel survey (TU) is to survey the transport behaviour of Danes residing in Denmark.
TU is an individual survey, because most applications regard either individual behaviour or general statistics and because the response rate is an issue. Yet, it was conducted household surveys in a scientific context in 2005 and 2011. However, the ordinary questionnaire contains background information on the composition of the household, plus questions on co-participants in each trip.
TU contains a one-day travel diary, because most applications regard either daily behaviour or general statistics. The priority is to get good and detailed information on that single day. In 2010-11, there has been conducted a special survey with a 14-day and/or a 3-month diary. Besides this, the questionnaire asks supplementary questions about overnight trips such that TU can be used for analysing these.
TU covers 365 days a year, because we want a complete picture, and because some of the partners have particular interest in non-working days. TU regards Danish residents, 10-84 years of age. Danish residents are chosen for practical reasons. The age limits are historically motivated. The lower limit of 10 years might be explained by the observation that children under 10 are difficult to interview and have only few trips on their own. The questionnaire contains questions on co-participants in each trip, which to some extent allows analysis of children below the age of 10.
TU is a combination of internet and telephone interviews. Originally this concept was developed in order to save money, but experience has shown that the combination has positive influence on the quality of the data.
TU has no separate long distance part. Using our ordinary sampling techniques, we collect data for thousands of long distance trips.
There are some examples of TU results:
In TU, the car ‘ownership’ questions are phrased as car availability at household level, and then a supplementary question on the ownership for each car. The car ownership can thus be estimated as the household-owned cars, counted at household level. This can be compared to the figure for household-owned cars from Statistics Denmark. To make the comparison, it has been necessary to add the figures for cars and vans, because TU and Statistics Denmark apply two different definitions of cars vs. vans.
The February 2009 questionnaire contained a minor improvement to the car availability question. Before Feb’ 09, the question was phrased “please list the cars available to your household”. After the change, the questionnaire now reads “how many cars are available to your household” and then “please specify”. This difference gives rise to a 10% increase in the “total cars”. There is no evidence of underrepresentation of cars in the newest TU data.