This document is a summary of the 2008 Status of the Nation's Highways, Bridges, and Transit: Conditions and Performance report to Congress (C&P report). The C&P report is intended to provide decision makers with an objective appraisal of the physical conditions, operational performance, and financing mechanisms of highway, bridge, and transit systems based both on the current state of these systems and on the projected future state of these systems under a set of alternative future investment scenarios. This edition of the C&P report is the eighth in the series that combines information on the Nation's highway and transit systems.
The main body of the report is organized into four major sections. Part I, "Description of Current System," includes the core retrospective analyses in the report, including chapters on the role of highways and transit, system characteristics, system conditions, operational performance, safety, and finance.
Part II, "Investment/Performance Analysis," includes the core prospective analyses of the report, including projections of future highway, bridge, and transit capital investment under certain defined scenarios. This section also explores how these scenarios would be affected by changing the assumptions about travel growth, financing mechanisms, and other key variables.
The highway investment scenarios presented 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 model quantifies user, agency, and societal costs for various types and combinations of improvements, including travel time, vehicle operating, safety, capital, maintenance, and emissions costs.
Bridge investment scenario estimates were developed from the National Bridge Investment Analysis System (NBIAS) model, which was used for the first time in the 2002 edition of the C&P report. Unlike previous bridge models (and similar to HERS), NBIAS incorporates benefit-cost analysis into the bridge investment/ performance evaluation.
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 in order to select future investments.
Part III, "Special Topics," explores further some topics related to the primary analyses in the earlier sections of the report. Some of these chapters reflect recurring themes that have been discussed in previous editions of the C&P report, while others address new topics of particular interest that will be included in this edition only. Part IV, "Afterword: A View to the Future," identifies potential areas for improvement in the data and analytical tools used to produce the analyses contained in this report and describes ongoing research activities.