12: Postal, Telephone, and Face-to-Face Surveys: How Comparable are They?

The problem of the comparability of the data from different survey modes is obviously not new (De Leeuw, 1992; De Leeuw and Van der Zouwen, 1992). However, there have been very few experiments with a rigorously controlled methodological framework that aim to compare different survey modes with regard to travel diaries. The issue is nevertheless of current importance. The development of survey techniques, particularly as a result of new technology, has made it increasingly doubtful that existing survey methods for periodic surveys can remain unchanged. The development of international exchanges encourages projects which compare data obtained in different places at different times (European projects in particular). The general tendency for response rates to fall casts doubt on the survey modes that are selected and also makes it necessary to combine different survey modes to increase response rates. This list is obviously not exhaustive, but illustrates the importance of this issue.