U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
Conditions and Performance
Status
of the Nation's Highways, Bridges, and Transit:
2002 Conditions and Performance Report
|
Exhibit 11-35:
Year of Construction and Cumulative ADT - Timber Superstructure Bridges
Exhibit 11-35 is a bar graph that shows the construction of timber superstructure bridges. The vertical axis measures number of bridges from 0 to 4,000 in increments of 500 bridges. The horizontal axis has 21 bars, one for each 5-year period between 1900 and 2000. New timber superstructure bridges were at 1,000 before 1900. They were 200 or less for each period to 1925, then rose sharply to 900 by 1930 and more than 2,700 by 1940. The figure dropped during WWII, then rose steadily again to a peak of 3,700 in 1956-60. The bars then decline steadily to 1,550 in 1981-85, rise to 1,800 by 1990, and drop to 800 in 2000. There are also two lines and a second vertical axis (measuring percentages from 0 to 100 in increments of 10 percent) in this chart. The first, representing cumulative percent of structure population, rises slowly from 0 to 20 percent by 1940, 50 percent by 1960, 80 by 1980, and 100 by 2000. The other line, representing cumulative percentage of ADT, parallels the first line, give or take 1 to 5 percentage points.
Source: National Bridge Inventory.
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Page last modified on November 7, 2014
