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

Chapter 11: Federal Bridge Program Status of the Nation's Bridges
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Index
Introduction
Highlights
Executive Summary
Part I: Description of Current System
Ch1: The Role of Highways and Transit
Ch2: System and Use Characteristics
Ch3: System Conditions
Ch4: Operational Performance
Ch5: Safety Performance
Ch6: Finance

Part II: Investment Performance Analyses
Ch7: Capital Investment Requirements
Ch8: Comparison of Spending and Investment Requirements
Ch9: Impacts of Investment
Ch10: Sensitivity Analysis

Part III: Bridges
Ch11: Federal Bridge Program Status of the Nation's Bridges

Part IV: Special Topics
Ch12: National Security
Ch13: Highway Transportation in Society
Ch14: The Importance of Public Transportation
Ch15: Macroeconomic Benefits of Highway Investment
Ch16: Pricing
Ch17: Transportation Asset Management
Ch18: Travel Model Improvement Program
Ch19: Air Quality
Ch20: Federal Safety Initiatives
Ch21: Operations Strategies
Ch22: Freight

Part V: Supplemental Analyses of System Components
Ch23: Interstate System
Ch24: National Highway System
Ch25: NHS Freight Connectors
Ch26: Highway-Rail Grade Crossings
Ch27: Transit Systems on Federal Lands

Appendices
Appendix A: Changes in Highway Investment Requirements Methodology
Appendix B: Bridge Investment/Performance Methodology
Appendix C: Transit Investment Condition and Investment Requirements Methodology
List of Contacts

Specific Bridge Types

The following areas are addressed in this section of the chapter:

  • Additional detail on Interstates, other arterials, collectors and local bridges.
  • Characterization of the superstructure material types used in the bridge network.
  • Examination of the age distribution, deficiency percentages, and deficiency trends for each superstructure material (concrete, steel, prestressed concrete, timber, and other).

Year of Construction by Functional Classification

The year of construction distribution was presented for all structures in the National Bridge Inventory. Distributions were created for Interstates (see Exhibit 11-13), other arterials (see Exhibit 11-14), collectors (see Exhibit 11-15), and local (see Exhibit 11-16) bridges. There is a distinct peak in the distribution of Interstate bridges with the average year of construction in the mid 1960's. Other functional classifications have much greater dispersion in the year of construction.

Interstate Bridges
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Other Arterial Bridges
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Collector Bridges
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Local Bridges
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Superstructure Material Types

Predominant materials used for bridge superstructures are steel, concrete, prestressed concrete, and timber. Other materials, such as aluminum, iron, and composite materials, are utilized on less than 1 percent of the structures. The percentage of superstructure materials utilized is shown in Exhibit 11-17 weighting bridges equally (by numbers), weighting by the traffic carried (ADT), and weighting by the size of the structure (by deck area). Steel bridges tend to be utilized for longer than average structures carrying higher volumes of traffic than average. Timber bridges, which constitute 5.7 percent of the inventory by numbers, carry small volumes of traffic and are smaller than average in terms of deck area. Material percentages are shown for Interstates, other arterials, collectors and local functional classifications in Exhibit 11-18.

Bridges by Type of Superstructure Material
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Bridges by Type of Superstructure Material and Functional Class
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The number and percentage of bridges by superstructure material, owner, and functional classification are shown in Exhibit 11-19. Figures include both rural and urban designations. Exhibit 11-20 shows the percentages of material type used for the varying functional classifications and owners for rural bridges. Exhibit 11-21 shows the same information for urban bridges.

    
Exhibit 11-19

Bridges by Type of Superstructure Material, by Owner and Functional Classification
 
FUNCTIONAL CLASS MATERIAL FEDERAL STATE LOCAL PRIVATE ALL OWNERS
Interstate
Concrete 12 (52%) 20,088 (37%) 58 (20%) 40 (10%) 20,198 (36%)
Prestressed 3 (13%) 13,288 (24%) 24 (8%) 5 (1%) 13,320 (24%)
Steel 8 (35%) 21,295 (39%) 211 (71%) 349 (89%) 21,863 (39%)
Timber 0 (0%) 6 (0%) 2 (1%) 0 (0%) 8 (0%)
Other 0 (0%) 53 (0%) 1 (0%) 0 (0%) 54 (0%)
Other Arterial
Concrete 216 (37%) 56,326 (48%) 10,088 (49%) 141 (22%) 66,782 (48%)
Prestressed 126 (22%) 25,980 (22%) 4,725 (23%) 131 (20%) 30,979 (22%)
Steel 196 (34%) 33,556 (29%) 5,076 (25%) 352 (54%) 39,249 (28%)
Timber 32 (5%) 825 (1%) 339 (2%) 11 (2%) 1,209 (1%)
Other 12 (2%) 369 (0%) 264 (1%) 12 (2%) 658 (0%)
Collector
Concrete 759 (61%) 40,496 (55%) 37,686 (45%) 64 (16%) 79,014 (50%)
Prestressed 263 (21%) 11,739 (16%) 16,735 (20%) 58 (15%) 28,836 (18%)
Steel 170 (14%) 19,763 (27%) 23,719 (29%) 224 (57%) 43,945 (28%)
Timber 27 (2%) 1,741 (2%) 4,508 (5%) 44 (11%) 6,324 (4%)
Other 19 (2%) 319 (0%) 520 (1%) 6 (2%) 867 (1%)
Local
Concrete 1,957 (26%) 8,319 (26%) 62,647 (32%) 179 (18%) 73,199 (31%)
Prestressed 1,234 (17%) 6,733 (21%) 35,537 (18%) 110 (11%) 43,651 (18%)
Steel 1,751 (24%) 15,996 (49%) 73,284 (38%) 473 (47%) 91,592 (39%)
Timber 2,452 (33%) 1,222 (4%) 22,423 (11%) 235 (23%) 26,350 (11%)
Other 56 (1%) 233 (1%) 1,529 (1%) 9 (1%) 1,829 (1%)
All Urban Bridges
Concrete 2,944 (32%) 125,229 (45%) 110,479 (37%) 424 (17%) 239,193 (41%)
Prestressed 1,626 (17%) 57,740 (21%) 57,021 (19%) 304 (12%) 116,786 (20%)
Steel 2,125 (23%) 90,610 (33%) 102,290 (34%) 1,398 (57%) 196,649 (33%)
Timber 2,511 (27%) 3,794 (1%) 27,272 (9%) 290 (12%) 33,891 (6%)
Other 87 (1%) 974 (0%) 2,314 (1%) 27 (1%) 3,408 (1%)
Source: National Bridge Inventory.

Rural Superstructure Materials by Owner and Functional Classification
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Urban Superstructure Materials by Owner and Functional Classification
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Exhibits 11-20 and 11-21 present the superstructure material percentages for rural and urban designations respectively. Notable differences can be seen in the Interstate bridge population with significantly higher percentages of urban Interstates constructed with steel. Prestressed superstructure bridges also constitute a higher percentage of the inventory in urban environments. Concrete (excluding prestressed concrete) is the dominant material for rural bridges. Timber superstructure bridges are prevalent in rural areas and not common in urban environments.

Concrete Superstructure Bridges (Excluding Prestressed Concrete)

The average age of concrete bridges in the NBI is approximately 40 years with an average year of construction of 1961. The average age of bridges for each combination of ownership and functional classification may be determined in Exhibit 11-22. The year of construction distribution and cumulative ADT are shown in Exhibit 11-23 for all concrete superstructure bridges (exclusive of prestressed concrete). Deficiencies and deficiency trends are shown in Exhibits 11-24 and 11-25 respectively for reinforced concrete superstructure bridges.

    
Exhibit 11-22

Average Year of Construction and Standard Deviation for Concrete Bridges by Functional Classification and Ownership
 
FUNCTIONAL CLASS AVERAGE YEAR OF CONSTRUCTION (AND STANDARD DEVIATION)
FEDERAL STATE LOCAL PRIVATE ALL OWNERS
Rural Bridges
Interstate
1964
(2)
1965
(10)
1943
(38)
1954
(9)
1965
(10)
Other Arterials
1958
(22)
1955
(21)
1971
(26)
1955
(23)
1956
(22)
Collectors
1959
(17)
1957
(20)
1962
(22)
1941
(28)
1959
(21)
Local
1960
(18)
1960
(22)
1965
(26)
1950
(36)
1964
(26)
All Rural
1960
(18)
1958
(20)
1964
(25)
1949
(32)
1961
(22)
Urban Bridges
Interstate
 
 
1966
(10)
1968
(20)
1967
(18)
1966
(10)
Other Arterials
1962
(18)
1959
(20)
1962
(23)
1943
(24)
1960
(21)
Collectors
1950
(11)
1958
(22)
1964
(25)
1935
(25)
1962
(24)
Local
1952
(19)
1964
(21)
1965
(24)
1949
(36)
1965
(24)
All Urban
1954
(18)
1961
(18)
1964
(24)
1948
(30)
1962
(21)
All Structures
1959
(18)
1958
(20)
1964
(25)
1948
(30)
1961
(22)
Source: National Bridge Inventory.

Year of Construction and Cumulative ADT - Concrete Superstructure Bridges (excluding prestressed concrete superstructures)
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Percent Deficient - Concrete Superstructure Bridges
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Year of Construction and Cumulative ADT - Deficient Concrete Superstructure Bridges (excluding prestressed concrete superstructures)
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Steel Superstructure Bridges

The average age of steel bridges in the NBI is approximately 44 years with an average year of construction of 1958. The average age of bridges for all combinations of functional classification and ownership may be determined through examination of Exhibit 11-26. The year of construction distribution and cumulative ADT for all steel superstructure bridges are shown in Exhibit 11-27. Deficiencies and deficiency trends are shown in Exhibits 11-28 and 11-29 respectively for steel superstructure bridges.

    
Exhibit 11-26

Average Year of Construction and Standard Deviation for Steel Bridges by Functional Classification and Owner
 
FUNCTIONAL CLASS AVERAGE YEAR OF CONSTRUCTION (AND STANDARD DEVIATION)
FEDERAL STATE LOCAL PRIVATE AVERAGE
Rural Bridges
Interstate
1960
(10)
1967
(10)
1967
(28)
1965
(16)
1967
(10)
Other Arterials
1965
(19)
1960
(20)
1961
(29)
1951
(18)
1960
(20)
Collectors
1963
(20)
1958
(20)
1956
(23)
1945
(24)
1957
(22)
Local
1964
(21)
1963
(21)
1953
(29)
1936
(28)
1955
(28)
All Rural
1964
(21)
1961
(19)
1954
(28)
1942
(26)
1957
(25)
Urban Bridges
Interstate
1967
(8)
1969
(11)
1959
(10)
1965
(13)
1969
(11)
Other Arterials
1947
(31)
1965
(18)
1956
(25)
1947
(23)
1963
(21)
Collectors
1955
(14)
1965
(19)
1955
(25)
1949
(30)
1959
(23)
Local
1955
(20)
1967
(19)
1955
(27)
1944
(33)
1958
(25)
All Urban
1953
(23)
1967
(16)
1955
(26)
1953
(25)
1964
(20)
All Structures
1963
(21)
1963
(18)
1954
(27)
1949
(26)
1958
(24)
Source: National Bridge Inventory.

Year of Construction and Cumulative ADT - Steel Superstructure Bridges
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Percent Deficient - Steel Superstructure Bridges
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Year of Construction and Cumulative ADT - Deficient Steel Superstructure Bridges
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Prestressed Concrete

Prestressed concrete was introduced in the middle of the 20th Century, and today the majority of bridges are constructed using prestressed concrete designs. The average age of prestressed concrete bridges in the NBI is approximately 24 years with an average year of construction of 1978. There are no significant differences in the age of rural versus urban prestressed bridges. The average age of bridges for all combinations of functional classification and ownership is shown in Exhibit 11-30. The year of construction distribution and cumulative ADT are shown in Exhibit 11-31 for all prestressed concrete superstructure bridges. Deficiencies and deficiency trends are shown in Exhibits 11-32 and 11-33 respectively for concrete superstructure bridges.

    
Exhibit 11-30

Average Year of Construction and Standard Deviation for Concrete Bridges by Functional Classification and Ownership
 
FUNCTIONAL CLASS AVERAGE YEAR OF CONSTRUCTION (AND STANDARD DEVIATION)
FEDERAL STATE LOCAL PRIVATE AVERAGE
Rural Bridges
Interstate
1968 (5) 1973 (10) 1996       1973 (10)
Other Arterials
1978 (12) 1980 (16) 1981 (17) 1972 (11) 1980 (16)
Collectors
1977 (11) 1978 (16) 1978 (17) 1982 (19) 1978 (16)
Local
1977 (13) 1979 (15) 1980 (17) 1981 (20) 1980 (17)
All Rural
1977 (13) 1978 (15) 1980 (17) 1979 (18) 1979 (16)
Urban Bridges
Interstate
    1975 (12) 1993 (6) 1973 (14) 1975 (12)
Other Arterials
1977 (11) 1979 (15) 1977 (18) 1979 (20) 1978 (16)
Collectors
1971 (13) 1975 (20) 1976 (19) 1982 (22) 1975 (20)
Local
1974 (19) 1978 (14) 1976 (19) 1975 (19) 1977 (18)
All Urban
1975 (17) 1977 (14) 1976 (19) 1978 (20) 1977 (16)
All Structures
1977 (13) 1978 (15) 1979 (17) 1978 (19) 1978 (16)
Source: National Bridge Inventory.

Year of Construction and Cumulative ADT - Prestressed Concrete Superstructure Bridges
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Percent Deficient - Prestressed Concrete Superstructure Bridges
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Year of Construction and Cumulative ADT - Deficient Prestressed Concrete Superstructure Bridges
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Timber Bridges

Timber bridges, as described previously, are primarily used in rural environments for small spans carrying small volumes of traffic. The average age of timber bridges in the NBI is 43 years with an average year of construction of 1959. There is no significant difference between the ages of the rural and the urban timber bridge populations. The average age of timber bridges for all combinations of functional classification and ownership is presented in Exhibit 11-34. The year of construction distribution and cumulative ADT are shown in Exhibit 11-35 for all timber superstructure bridges. Deficiencies and deficiency trends are shown in Exhibits 11-36 and 11-37 respectively for timber superstructure bridges.

    
Exhibit 11-34

Average Year of Construction and Standard Deviation for Timber Bridges by Functional Classification and Ownership
 
FUNCTIONAL CLASS AVERAGE YEAR OF CONSTRUCTION (AND STANDARD DEVIATION)
FEDERAL STATE LOCAL PRIVATE ALL OWNERS
Rural Bridges
Interstate
 
 
1960
(20)
1974
(18)
 
 
1963
(20)
Other Arterials
1956
(14)
1943
(12)
1970
(30)
1956
(33)
1949
(21)
Collectors
1955
(16)
1953
(15)
1958
(21)
1933
(21)
1956
(20)
Local
1964
(18)
1960
(22)
1959
(23)
1937
(25)
1959
(23)
All Rural
1964
(18)
1953
(18)
1959
(23)
1936
(25)
1959
(22)
Urban Bridges
Interstate
 
 
 
 
 
 
 
 
 
 
Other Arterials