Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Summary

Economics-Based Approach to Transportation Investments

Highway Investment Requirements

Bridge Investment Requirements

Combined Highway and Bridge Investment Requirements

Transit Investment Requirements

Comparison with Previous Reports

The projected average annual investment requirements shown for 1998-2017 in this report are not directly comparable to those shown for 1996-2015 in the 1997 C&P report, due to inflation, data corrections, model enhancements, and changes in the methodology used to develop the estimates. To facilitate direct comparisons between the two reports, the 1995 data used to develop the last report have been corrected and reprocessed through the current version of HERS, with the results restated in 1997 dollars. The adjustments to the 1995 data are discussed in Appendix G.

Exhibit 7-6 compares the investment requirement projection in this report with the original projections reported in the 1995 and 1997 C&P reports, as well as with the values obtained by reanalyzing the older data using the latest analytical procedures.

Exhibit 7-6. Comparison of Highway Investment Requirements 1995, 1997 and 1999 C&P Reports

Comparison with 1995 Data Used in the 1997 C&P Report

Keeping all other factors constant, highway investment requirements for the Maximum Economic Investment Scenario based on the 1997 HPMS data are 0.9 percent higher than the restated highway investment requirements based on the 1995 HPMS data. The small increase is largely the result of changes in the composition of highway spending between 1995 and 1997, which affects the external adjustment procedures for non-modeled expenditures as described earlier.

Highway investment requirements for the Maintain User Costs scenario based on the 1997 HPMS data are 11.8 percent higher than those based on the 1995 HPMS data, keeping all other factors constant. Part of this is attributable to the decline in delay discussed in Chapter 4. Travel time costs and total highway user costs are lower in 1997 than in 1995. Therefore "Maintaining User Costs" at their 1997 levels for 20 years is actually a more stringent standard that maintaining them at their 1995 levels for 20 years, and is therefore more expensive to achieve. This is an inherent shortcoming in any of the scenarios that "Maintain" a conditions or performance characteristic, that makes comparisons between reports difficult. As pavement conditions, highway-user costs, and travel time costs change over time, the targets for the Maintain Conditions scenario, the Maintain User Costs benchmark, and the Maintain Travel Time benchmark also change.

Appendix G includes a discussion of the source of the differences between the original investment requirement projections reported in the 1997 C&P report using 1995 HPMS data, and the updated values using the latest analytical approach.

Comparison with 1993 Data Used in the 1995 C&P Report

Keeping all other factors constant, highway investment requirements for the Maximum Economic Investment Scenario based on the 1997 HPMS data are only 0.4 percent higher than the restated highway investment requirements based on the 1993 HPMS data. Highway investment requirements for the Maintain Conditions scenario based on the 1997 HPMS data are 6.7 percent higher than those based on the 1993 HPMS data, keeping all other factors constant. This is partially the result in the improvement in pavement condition since 1993, which makes "Maintaining Conditions" at their 1997 level a more stringent standard. The increase is also influenced by changes in the composition of highway spending between 1995 and 1997, which affects the external adjustment procedures for non-modeled expenditures as described earlier.

The Maintain Conditions projection using the re-analyzed 1993 HPMS data, $47.6 billion in 1997 dollars, is lower than the original projection of $49.7 billion in 1993 dollars for the Cost-to-Maintain scenario in the 1993 C&P Report. This is partially the result of changes in the scenario definition, but mainly the differences are the result of incorporating the procedures contained in the most recent Highway Capacity Manual 1994 (Special Report 209 of the Transportation Research Board), as discussed on page 61 of the 1997 C&P report. These reductions more than offset the effects of inflation on the projections.