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

Highway Conditions

Chapter 3 discusses the current highway and bridge conditions for all functional systems, including Interstate highways. Exhibits 3-9 and 3-10 show trends in pavement condition for Rural Interstates and Urban Interstates from 1993 to 1997. The 1997 data are highlighted in Exhibit A-1.

In 1997, 96.3 percent of rural Interstate mileage met the Federal Highway Administration 1998 National Strategic Plan standard for "acceptable ride quality" having an International Roughness Index (IRI) value of less than or equal to 170 inches per mile. The remaining 3.7 percent of rural mileage is identified as having "poor" pavement in Exhibit A-1. Of urban Interstate mileage, 90.8 percent was classified as having "acceptable ride quality" and the remaining 9.2 percent is identified as "poor" pavement in Exhibit A-1. The percentage of Interstate pavement with acceptable ride quality has increased in recent years.

Exhibit A-1

Interstate Pavement Condition, by Percent Total Miles, 1997

The average IRI reported for HPMS sample sections on rural Interstates was 93 inches per mile, which falls in the "good" range in Exhibit A-1. The average IRI for urban Interstate sections was 114, which would be classified as "fair."

Lane Widths, Curves, Grades, and Access Control

Chapter 3 also discusses other factors that affect the level of service and safety of the highway system. [See Exhibits 3-14, 3-15, 3-17, and 3-18.] Rural and Urban Interstate Lane Width are shown in Exhibit A-2. In 1997, 99.8 percent of rural interstate mileage had lane widths of 12 feet or wider. For urban Interstate mileage, 99.4 percent met or exceeded the 12 foot standard.

Exhibit A-2

Rural and Urban Interstate Lane Width, 1997

Exhibit A-3 shows the horizontal and vertical alignment adequacy for rural Interstate highways. Of total rural Interstate highways mileage, 95.5 percent is rated as "Code 1" for horizontal alignment, meaning that all curves meet appropriate design standards. The remaining 4.5 percent are below design standards. For vertical alignment, 93.0 percent of rural Interstate mileage is rated as "Code 1," meaning that all grades meet appropriate design standards. The remaining 7.0 percent are below design standards.

Exhibit A-3. Rural Interstate Horizontal and Vertical Alignment, 1997

The vast majority of Interstate mileage consists of divided highways with at least four lanes and full access control. However, in 1997 there were 1,100 miles of rural interstate that did not meet this standard, concentrated mainly in Alaska. None of Alaska's 1,034 rural Interstate miles meet this criteria. For urban Interstates, 104 miles do not meet the criteria specified; 53 of these miles are in Puerto Rico.