This report from the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies, explores predictive relationships between highway improvements and travel time reliability. How can the effect of an improvement on reliability be predicted? Alternatively, how can reliability be characterized as a function of highway, traffic, and operating conditions? The report presents two models that can be used to estimate or predict travel time reliability. The models have broad applicability to planning, programming, and systems management and operations.
