Travel time variability: a review of theoretical and empirical issues

Over the past several years a number of research projects have attempted to empirically measure behavioural responses to changes in travel time variability. These have generally been built on theoretical models of scheduling choice that account for changes in departure time in response to the expected costs associated with variability. This paper reviews both the theory and empirical results of several projects that estimated coefficients on various measures of variability using stated preference techniques. Gaps in the understanding of these issues are identified and discussed.