Overview
Adding transportation capacity improves safety, accessibility, and the economic health of a region but often comes with an economic, social, or environmental price. The public is aware of the price and must be convinced that new capacity is really needed before they will support expansion. This implies that operational improvements to the roadway may be warranted to improve efficiency some years before a major capacity expansion is proposed. This report addresses the question, What gains in sustainable flow can be obtained from operational improvements to roadways? The report uses the term sustainable flow rather than capacity, to avoid confusion with other definitions of capacity. The researchers used enhanced simulation methods and network diagnostics, including travel time and travel time reliability, to test various types of operational improvements.