Conditions and Performance Chapter Listing

Conditions and Performance Home Page

Introduction

Background

Current Conditions and Performance

Projected Conditions and Performance in 2007

Resources Needed to Maintain and Improve the Interstate System

Addressing Interstate System Needs

Expected Rural Interstate Bridge Conditions in 2007

Chapter 7 defined the bridge investment backlog as the cost of improving all bridges that are currently deficient. The current investment requirement backlog includes the costs to repair or replace all bridges identified as functionally obsolete or structurally deficient in Exhibit A-4, as well as the costs of additional repairs or partial replacements required to correct less severe problems with individual bridge components. (These less severe problems are described in BNIP as "condition deficiencies," and includes such items as bridge decks in need of rehabilitation. However, this term is not widely utilized, and is not referenced elsewhere in this study to avoid confusion with the common definition of "bridge deficiencies" which includes only structural and functional deficiencies.)

The BNIP model estimates that the current investment backlog on rural Interstate bridges is $6.3 billion. This section examines the effect that different levels of investment would be expected to have on the size of this backlog. All dollar values cited in this analysis are stated in constant 1997 dollars.

Exhibit A-13 projects the percent of rural Interstate bridges that would be deficient in 2007, the total percent of rural Interstate bridges needing to be repaired or replaced in 2007, and the cost to address these structural deficiencies, functional deficiencies, and other bridge needs. Exhibit A-5 shows that all levels of government spent approximately $0.4 billion for the repair, rehabilitation and replacement of existing rural Interstate bridges in 1997. If this level of investment were sustained over the next 10 years, cumulative investment for the 1998-2007 period would be approximately $3.9 billion (stated in 1997 dollars).

Exhibit A-13. Projected Rural Interstate Bridge Investment Backlog in 2007, for Different Possible Funding Levels

Effects of Investing at 1997 Spending Levels

The pattern of investments recommended by BNIP is intended to minimize the investment requirement backlog, rather than the number of deficient bridges or the total number of bridges needing repairs. If current funding levels were sustained in constant dollar terms over the next 10 years, and $3.9 billion were invested in bridges, the model predicts the bridge investment backlog would increase from $6.3 billion to $6.8 billion. The percent of bridges that are deficient would fall from 16.4 percent to 10.6 percent. However, the total percent of bridges needing repairs (including deficient bridges as well as bridges with less severe problems) would rise from 30.9 percent to 47.5 percent. These results suggest that the BNIP model is choosing to address a smaller number of severe deficiencies that are expensive to correct, while it is letting a number of less severe problems to continue to accrue.

Investment Required to Eliminate or Maintain the Bridge Investment Backlog

The top row in the table in Exhibit A-13 represents the cost to eliminate the rural Interstate bridge investment backlog by 2007. To achieve this would require a cumulative 10-year investment of $9.9 billion on rural Interstate highways. This level of investment would address all structural deficiencies, functional deficiencies, and all other less severe bridge condition problems identified by BNIP.

To maintain the bridge investment backlog at its 1997 level would require a 10-year investment of $4.4 billion. Based on the pattern of investment recommended by BNIP, this level of investment would reduce the percent of deficient bridges from 16.4 percent to 9.7 percent. The percent of bridges with condition problems that eventually would need to be repaired would rise to 43.9 percent.

Projected Bridge Investment Backlog at Forecast Funding Levels for 1998-2007

Exhibit A-6 shows that 0.8 percent of total highway capital outlay by all levels of government was used for rural Interstate bridge repair, rehabilitation, or replacement in 1997. If this percentage remains constant, and total highway and bridge capital outlay for 1998-2007 on all functional systems reaches $557.5 billion in constant 1997 dollars, approximately $4.6 billion would be spent on rural Interstate bridges. At this level of investment, the rural Interstate bridge investment backlog in 2007 would be expected to be between 0.0 and 5.1 percent lower than the current level.