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Status of the Nation's Highways, Bridges, and Transit:
2002 Conditions and Performance Report

Exhibit 11-12:

Year of Construction and Cumulative ADT - All Superstructure Materials

Exhibit 11-12

Exhibit 11-12 is a bar graph that shows year of construction and cumulative ADT for all superstructure materials. The vertical axis measures number of bridges from 0 to 60,000 in increments of 10,000 bridges. The horizontal axis has 21 bars, one for each 5-year period between 1900 and 2000. Each bar has three parts, measuring the distribution of functionally obsolete, structurally deficient, and non-deficient bridges. In the first quarter of the 20th century, about half the Nation's new bridges were structurally deficient, about a third were non-deficient, and the balance were obsolete. From 1926 to 1950, about half the Nation's new bridges were non-deficient, a third were structurally deficient, and the balance were obsolete. From 1951 to 1975, between two-thirds and three-quarters of the Nation's new bridges were non-deficient, with the rest split about evenly between obsolete and structurally deficient. From 1976 to 1990, about five-sixths of the Nation's new bridges were non-deficient, about one-tenth were obsolete, and the balance were structurally deficient. And from 1991 to 2000, nearly all of the Nation's new bridges were non-deficient. There are three other items and a second vertical axis (measuring percentages from 0 to 100 in increments of 10 percent) in this chart. A line, representing the "linear" percent of deficient bridges for each year of construction by ADT, starts in 1900 at about 72 percent and drops in a straight line to 50 percent by 1950, 25 by 1970, 10 by 1990, and just over 0 by 2000. A series of small squares, representing the percent of deficient bridges for each year of construction by ADT, starts at about 53 percent, climbs to 66 percent by 1910, then drops steadily to 50 percent by 1930, 35 by 1960, 20 by 1975, and 0 by 2000. And a series of small triangles, representing the percent of deficient bridges for each year of construction by numbers, starts at about 58 percent, climbs to 75 percent by 1910, then drops steadily to 50 percent by 1930, 35 by 1960, 20 by 1975, and 0 by 2000.
Source: National Bridge Inventory.


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