This concluding paper discusses key aspects of the five research papers presented at this Roundtable in terms of their policy applications. It notes problems concerning how policy makers make use of economic analysis findings, and then summarizes the breadth of macro-, meso- and micro-economic methods in terms of their predictive use for infrastructure assessment and planning. It then examines tradeoffs and limitations among all the methods that affect their policy application, and it identifies directions needed to enhance the applicability of future economic models for policy makers.