of the Nation’s Highways, Bridges, and Transit:
|Chapter 3: System Conditions|
Part I: Description of Current System
Part II: Investment Performance Analyses
Part III: Bridges
Part IV: Special Topics
Part V: Supplemental Analyses of System Components
Exhibit 3-1 highlights the key highway and transit statistics discussed in this chapter, and compares them with the values from the last report. The first column contains the values reported in the 1999 C&P report, based on 1997 data. Data revisions are shown in the second column. The third column provides comparable values based on 2000 data.
Comparison of System Conditions Statistics with Those in the 1999 Report
The pavement conditions reported in this chapter include all functional classifications except rural minor collectors and local roads. Pavement conditions are presented for three population groupings: Rural, Small Urban Areas (population less than 50,000), and Urbanized (population greater than 50,000). In previous editions of this report the overall pavement conditions were presented based on the qualitative condition terms “very good,” “good,” “fair,” “mediocre,” and “poor.” This edition adopts simplified terminology used in the annual FHWA Performance Plan and other FHWA reports. Pavement is classified as having either “acceptable” or “not acceptable” ride quality, and within the “acceptable” category some pavement is classified as “good”. These ratings are derived from one of two measures: International Roughness Index (IRI) or Present Serviceability Rating (PSR). The definitions for IRI and PSR, the relationship between these two measures, and the relationship between the new categories are discussed later in the chapter.
In 2000, 86.0 percent of measured roads had acceptable ride quality including 43.5 percent that met the standard for good condition. Since 1997, there was a slight increase in the percentage of miles in the good category. There was also an increase in the percentage of miles in acceptable condition. Pavement condition on the Interstate system improved since 1997. The percentage of rural, small urban, and urbanized Interstates with acceptable ride quality increased by 0.4 percent to 96.6 percent between 1997 and 2000.
The common indicator used to evaluate the condition of the Nation’s bridges was the number of deficient bridges. Under this metric, there were two types of deficient bridges: structurally deficient and functionally obsolete. In 1994, 32.5 percent of the Nation’s bridges were deficient. In 2000, 28.5 percent of the Nation’ bridges were deficient. Of the total number of bridges in 2000, 14.8 percent were structurally deficient while 13.8 percent were functionally obsolete. In urban areas, 31.9 percent of bridges were deficient, while in rural areas 27.6 percent were deficient. Local government agencies own over half of the deficient bridges.
The number of deficient bridges on our highway system has been steadily declining. Since 1995, the percentage of deficient bridges decreased from 31.4 percent to 29.6 percent. The percentage of deficient bridges on the Interstate system decreased from 24.7 percent to 21.6 percent while the percentage of deficient bridges on other arterials decreased from 27.6 percent to 25.8 percent.
A third indicator of bridge condition is deck area deficiency; this measure is increasingly used by engineers and policy analysts to describe bridge integrity. FHWA’s FY 2002 Performance Plan, for example, includes an indicator on deck area deficiency for NHS and non-NHS bridges. As Exhibit 3-34 describes, the nationwide percentage of bridge deck area described as deficient dropped from 30.9 percent in 1996 to 27.9 percent in 2000. Bridges with unknown or unclassified ownership had the largest percentage of deficient deck area (42.8 percent in 2000), followed by privately owned bridges (33.8 percent). Federally owned bridges had the smallest percentage of deficient deck area (25.8 percent in 2000).
In 2000, 27.9 percent of the Nation’s bridge deck area was considered deficient. The percentage of deficient bridge deck area decreased on every functional system from 1996 to 2000. Rural Interstate bridges had the smallest deficient deck area in 2000 (about 15 percent), while urban collector bridges had the largest deficient deck area (39.6 percent).
The condition of transit vehicles did not change significantly between 1997 and 2000. On a scale of 1 (poor) to 5 (excellent), bus vehicles had an average condition of 3.07 in 2000, up from 2.96 in 1997. The average condition of rail vehicles was 3.55 in 2000, down from 3.61 in 1997. Both the 1997 and 2000 ratings are lower than the 3.80 rating of rail vehicles reported in 1987. The average rail vehicle condition of 4.0 that was reported in the 1999 C&P Report for 1997 was subsequently revised downward to reflect a correction in the decay curve function for rail vehicles, excluding commuter rail. This revision was based on an updated and larger set of condition data collected by FTA in 1999, 2000, and 2001.
The percentage of bus maintenance facilities in adequate or better condition declined to 71 percent in 2000 from 77 percent in 1997. The percentage of rail maintenance facilities in adequate or better condition also fell from 77 percent in 1997 to 64 percent in 2000. The condition of yards has also declined. In 2000, 50 percent of all yards were in good condition and 50 percent were in adequate condition, compared with 63 percent in good condition and 37 percent in adequate condition in 1997. While the percentage of stations estimated to be in adequate or better condition has increased from 77 percent in 1997 to 84 percent in 2000, the percentage in good or better condition has declined from 54 percent in 1997 to 34 percent in 2000. These changes have resulted largely from the application of the newly estimated decay curve based on rail maintenance facility decay curves rather than in a change in the actual condition level of stations. Rail track conditions are estimated to have remained constant since 1997, with 83 percent of all track estimated to be in good or better condition in both 1997 and 2000.