This paper reviews modeling frameworks and empirical evidences on the valuation of travel time variability and summarizes the issues which are needed to work on the economic appraisal of transport infrastructure. In the literature review, we introduce the two classes of the modeling approaches: the mean-variance approach and the scheduling approach and continue with a discussion of their relative advantages and disadvantages. We further introduce a new integrated approach, which has some nice properties for economic appraisals. The summary of future issues are mainly dedicated to forecasting travel time variability, extension of the behavioral model and the aspects of behavioral economics in the stated preference survey.