This report presents findings from a project concluded during 1989 by staff from the University of Leeds, John Bates Services, Transport Planning Associates and the University of Oxford. The study began with a review of existing evidence on the nature and size of responses to highway improvements and supplemented this by a questionnaire survey to establish current opinion amongst informed experts. This suggested that despite a considerable amount of work in the UK and elsewhere, there is not yet a consensus as to the impact of new highway schemes on traveller behaviour, although there is, rightly or wrongly, a wide measure of agreement on certain aspects. Methods by which responses might be detected, and the accuracy with which they might be measured, have been reviewed, and strategies developed for measurement studies using, for example, traffic count data and roadside interview data. Costs have been calculated and recommendations made as to which monitoring strategies might best be adopted. Recommendations were also made in respect of the further analysis needed to improve estimates of sample size requirements and hence reduce survey costs.

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