Samenvatting
For the National Travel Survey until 1985 face-to-face interviews were used to collect data. Due to limited financial resources, from 1985 on data are used which are obtained by telephone/mail interviews. The authors were able to compare the results of both methods of interviewing on the basis of an experiment: in two specific months both a telephone/mail survey and a face-to-face survey were held. The estimates based on the group of telephone respondents and those based on the face-to-face respondents were not the same. It came out that the differences were significant and can to a large extent be explained by coverage errors, by the structure of the response and by the length of the reporting period. (Author/publisher)