Older versions of the reports in this series relied exclusively on engineering-based estimates for future investment requirements, which considered only the costs of transportation agencies. This philosophy failed to provide another critical dimension of transportation programs; that is, to provide service to users while minimizing overall costs. Executive Order 12893, Principles for Federal Infrastructure Investments, directs each executive department and agency with infrastructure responsibilities to base investments on "...systematic analysis of expected benefits and costs, including both quantitative and qualitative measures...". To address the deficiencies in earlier versions of this report and to meet the challenge of this executive order, new approaches to this analysis have been developed. The analytical tools now used in this report have added an economic overlay to the projection of future investment requirements. These newer tools use benefit/cost analysis to minimize the combination of capital investment and user costs to achieve different levels of highway performance.
Highway Economic Requirements System
The highway investment requirements in this report are developed in part from the Highway Economic Requirements System (HERS) which uses marginal benefit/cost analysis to optimize highway investment. The HERS addresses highway deficiencies by quantifying the agency and user costs of various types and combinations of improvements, including vehicle operating, travel time, and safety costs.
Transit Economic Requirements Model
The transit investment analysis is based on the Transit Economic Requirements Model (TERM). The TERM consolidates older engineering-based evaluation tools and introduces a benefit/cost analysis to ensure that investment benefits exceed investment costs. Specifically, TERM identifies the investments needed to replace and rehabilitate existing assets, improve operating performance, and expand transit systems to address the growth in travel demand, and then evaluates these needs on the basis of costs and benefits in order to select future investments.
National Bridge Investment Analysis System
This report introduces the National Bridge Investment Analysis System (BIAS) which adds an economic component to the bridge analysis. However, the bridge investment requirements still rely primarily on an older engineering-based model, the Bridge Needs and Investment Process.
The Bridge Needs and Investment Process (BNIP) is used to analyze bridge data from the National Bridge Inventory. This process identifies deficiencies based on engineering criteria, determines what action is required to correct the deficiencies, and estimates the costs of these actions. Cost effectiveness criteria are used to prioritize actions when funding is not sufficient to correct all deficiencies.