The Struggle to Hold Aging Bridges Together
The Braga Bridge.
Photo courtesy of Massachusetts Department of Transportation.
On March 17, 2008, inspectors for the Pennsylvania Department of Transportation discovered a widening crack in the pier of a bridge carrying Interstate 95 through Philadelphia. Immediately, they closed the interstate and began two days of emergency repairs.
"For those two days, 184,000 vehicles a day were forced on to side streets, and the national media carried pictures of the multi-lane interstate completely devoid of vehicles while nearby streets were jammed,” PennDOT Secretary Allen Biehler later told Congress.
Philadelphia pier crack.
Photo courtesy of Pennsylvania
Department of Transportation
PennDOT Secretary Allen Biehler gives press conference about the state of Pennsylvania’s bridges.
Photo courtesy of Pennsylvania Department of Transportation.
A month earlier, the Secretary said, a rural bridge in north central Pennsylvania, the Route 53 Irvona Bridge, was closed for a week after a routine inspection showed the steel beams needed immediate repairs.
In February 2008, the Birmingham Bridge which crosses the Monongahela River in Pittsburgh had to be closed for just over three weeks after two spans moved because of problems with the bridge’s rocker bearings. During the closure, 23,000 vehicles a day had to find alternate routes.
Biehler told a Congressional committee that PennDOT has tripled its annual bridge investment since 2003 for a total of $3.8 billion in repairs on 1,381 bridges. Despite this investment and because of the system’s age, the number of structurally deficient bridges has grown, from 5,587 to 6,034. In July 2008, Pennsylvanian leaders authorized a $350 million bond issue to repair 411 bridges.
Clearly, Secretary Biehler and his counterparts are struggling to hold together an aging inventory of bridges.
I-25 deteriorating girder.
Photo courtesy of New Mexico Department of Transportation
Missouri DOT Director Pete K. Rahn and Missouri Governor Matt Blunt inspect a bridge.
Photo courtesy of Missouri Department of Transportation.
In Missouri, of the 10,240 bridges on the state bridge system, some 1,093 are rated in serious or poor condition. Through a “Safe and Sound” bridge initiative, MoDOT Director Pete Rahn grouped 800 bridges into one package of projects which a contractor must not only build but finance. “The team will bring all the bridges up to good condition by the end of 2012 and will maintain them in good condition for at least 25 years,” said Rahn. Although the total construction cost of the program will be between $600 million and $800 million, the contractor will provide the financing through private activity bonds. Through this approach, the state will be able to fix 800 bridges in five years, while it normally could afford to fix only 40 per year.
The nation’s departments of transportation and their bridge engineers face a frustrating contradiction. They have better engineering, materials and construction techniques than ever before but stretched resources force them to make painful trade-offs to keep their bridges safe. They use emergency repairs, load limits and even closings as last-ditch efforts to protect the public.
What kind of investment gaps are states facing?
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Pennsylvania has asked the federal government for authorization to toll Interstate 80 to generate funds for highways and bridges, and Governor Edward G. Rendell has asked the Legislature to approve a proposed $12.8 billion, 75-year lease of the Turnpike to a private entity to generate a new annual funding stream for transportation.
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Maine recently forecast that if it doesn’t increase bridge investment by $50 million to $60 million annually, it will face an increasingly deteriorated bridge inventory. “Even at this level of investment, it is anticipated that bridge closures would need to occur on some low-priority, redundant bridges,” says the Maine report. In June 2008, legislators increased vehicle registration fees and approved a $160 million bonding program to repair Maine’s bridges.
North view of Brent Spence Bridge overlooking Cincinnati skyline.
Photo courtesy of Ohio Department of Transportation.
- The Oregon DOT is in the midst of a $1.3 billion program to replace nearly 300 critical bridges after a series of emergency repairs in the early 2000s alerted the public to the looming needs.
Schematic rendering of Arch Bridge.
Photo courtesy of Iowa Department of Transportation.
Local Governments Also Contend with Constant Bridge Repairs
States own 48 percent of the nation’s bridges, comprising 75 percent of the total deck area and carrying 87 percent of traffic. There are approximately 21,000 high-volume bridges which have more than 40,000 vehicle crossings each day, with 90 percent of those in urban areas.
Local governments—counties and municipalities—also own and maintain 300,444 bridges, constituting nearly a quarter of the total deck area, and carrying 12 percent of bridge traffic. Nearly a third of these bridges were rated structurally deficient (17 percent) or functionally obsolete (12 percent).
"Counties own 219,000 bridges, spanning rural and urban areas," said Larry E. Naake, Executive Director of the National Association of Counties. "Most travel starts and ends on local roads and we are in a constant cycle of maintenance and repair. Our bridges are obviously the linchpin in our entire system, but keeping these bridges safe and passable is becoming more and more difficult as construction costs soar and revenues fall."
In testimony before the House Committee on Transportation and Infrastructure last fall, Kathleen Novak, Mayor of Northglenn, Colorado, and Vice President of the National League of Cities, said that "allowing our bridges to deteriorate is a national calamity waiting to happen. The tragedy in Minneapolis reminds us that investment in our transportation system cannot be put aside to the future. Maintenance and continuous investment in improvements requires a renewed financial commitment at all levels of government and a long-term, comprehensive national plan for the future."
New Bridges Needed, Funding Unsure
In nearly every region of the country, states are planning for major bridge needs amidst uncertainty over when or if the construction funds will be available. New bridges are needed to relieve congestion and build new corridors in rapidly growing areas not adequately served by the Interstate Highway System.
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The Quad Cities region of Iowa and Illinois is separated by the Mississippi River. The existing bridges are too narrow for the traffic volumes and have become an impediment to the development and convenience of the region’s population. The citizens and DOTs from both states have agreed upon a state-of-the-art new arch bridge but are uncertain when the $1 billion will be available to construct it.
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In Corpus Christi, the Texas Department of Transportation is conducting an environmental impact statement to help determine how to replace the aging 50-year-old steel bridge which exists there. It estimates that a new structure could cost $500 million to $600 million and take as long as 2015 to open, once funding is determined.
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Similar stories exist for the proposed Great River Bridge between Arkansas and Mississippi, the Louisville Bridges, the Brent Spence Bridge in Cincinnati and the new Mississippi River Crossing in St. Louis.
How Are Bridge Conditions Rated?
According to the National Bridge Inspection Standards (NBIS), ratings are used to describe an existing bridge or culvert compared with its condition if it were new. Bridges are rated from 0 (failed condition) to 9 (excellent) on their “general” condition and on the condition of their primary components. The following components are rated:
- The bridge deck, including the wearing surface;
- The superstructure, including all primary load-carrying members and connections; and
- The substructure, including the abutments and all piers.
A condition rating of 4 or less on one of these items classifies a bridge as structurally deficient.
To be eligible for federal aid to replace a bridge, it must have a sufficiency rating of less than 50 and be either functionally obsolete or structurally deficient. To be eligible for repair, a bridge must have a sufficiency rating of less than 80. In both instances, federal aid must be matched by a state/local contribution. In the case of bridge repairs, if federal aid is used to repair a bridge, a jurisdiction cannot apply for federal assistance for any further repairs to this bridge for 10 years
What Does That Term Mean?
Bridge Sufficiency Rating A bridge sufficiency rating includes a multitude of factors: inspection results of the structural condition of the bridge, traffic volumes, number of lanes, road widths, clearances, and importance for national security and public use, as examples. The sufficiency rating is calculated by using a formula defined by the Federal Highway Administration. This rating indicates a bridge’s sufficiency to remain in service. The formula places 55 percent of its value on the structural condition of the bridge, 30 percent on its serviceability and obsolescence, and 15 percent on whether it is essential to public use. The point calculation is based on a 0–100 scale and compares the existing bridge to a new bridge designed to current engineering standards. The bridge’s sufficiency rating provides an overall measure of the bridge’s condition and is used to determine eligibility for federal funds. |
Functionally Obsolete Of the nation’s 590,000 bridges, a total of 73,000, about 12 percent, are rated as functionally obsolete. A functionally obsolete bridge is one that was built to standards that are not used today. These bridges are not automatically rated as structurally deficient, nor are they unsafe. Functionally obsolete bridges are those that do not have adequate lane widths, shoulder widths, or vertical clearances to serve current traffic demand, or those that may be occasionally flooded. A functionally obsolete bridge is similar to an older house. A house built in 1950 might be perfectly acceptable to live in, but it does not meet all of today’s building codes. Yet, when it comes time to consider upgrading that house or making improvements, the owner must look at ways to bring the structure up to current standards. |
Structurally Deficient Of the nation’s 590,000 bridges, some 80,000 are rated as structurally deficient, about 13 percent. Bridges are considered structurally deficient if:
Every bridge constructed goes through a natural deterioration or aging process, although each bridge is unique in the way it ages. The fact that a bridge is classified under the federal definition as “structurally deficient” does not imply that it is unsafe. A structurally deficient bridge, when left open to traffic, typically requires significant maintenance and repair to remain in service and eventual rehabilitation or replacement to address deficiencies. To remain in service, structurally deficient bridges are often posted with weight limits to restrict the gross weight of vehicles using the bridges. |
U.S. Bridges Per State, December 2007
| Number of Bridges | Structurally Deficient | Functionally Obsolete | Total Number of Deficient Bridges | Percentage of Total | |
| Alabama | 15,881 | 1,899 | 2,158 | 4,057 | 25.5% |
| Alaska | 1,229 | 155 | 179 | 334 | 27.2% |
| Arizona | 7,348 | 181 | 600 | 781 | 10.6% |
| Arkansas | 12,531 | 997 | 1,908 | 2,905 | 23.2% |
| California | 24,184 | 3,140 | 3,837 | 6,977 | 28.8% |
| Colorado | 8,366 | 580 | 824 | 1,404 | 16.8% |
| Connecticut | 4,175 | 358 | 1,042 | 1,400 | 33.5% |
| Delaware | 857 | 20 | 112 | 132 | 15.4% |
| District of Columbia | 245 | 24 | 128 | 152 | 62.0% |
| Florida | 11,663 | 302 | 1,692 | 1,994 | 17.1% |
| Georgia | 14,563 | 1,028 | 1,888 | 2,916 | 20.0% |
| Hawaii | 1,115 | 142 | 358 | 500 | 44.8% |
| Idaho | 4,104 | 349 | 452 | 801 | 19.5% |
| Illinois | 25,998 | 2,501 | 1,840 | 4,341 | 16.7% |
| Indiana | 18,494 | 2,030 | 2,004 | 4,034 | 21.8% |
| Iowa | 24,776 | 5,153 | 1,455 | 6,608 | 26.7% |
| Kansas | 25,461 | 2,991 | 2,372 | 5,363 | 21.1% |
| Kentucky | 13,637 | 1,362 | 2,928 | 4,290 | 31.5% |
| Louisiana | 13,342 | 1,780 | 2,180 | 3,960 | 29.7% |
| Maine | 2,387 | 349 | 468 | 817 | 34.2% |
| Maryland | 5,127 | 388 | 980 | 1,368 | 26.7% |
| Massachusetts | 5,018 | 585 | 1,987 | 2,572 | 51.3% |
| Michigan | 10,923 | 1,584 | 1,304 | 2,888 | 26.4% |
| Minnesota | 13,067 | 1,156 | 423 | 1,579 | 12.1% |
| Mississippi | 17,007 | 3,002 | 1,315 | 4,317 | 25.4% |
| Missouri | 24,071 | 4,433 | 3,108 | 7,541 | 31.3% |
| Montana | 4,980 | 473 | 541 | 1,014 | 20.4% |
| Nebraska | 15,475 | 2,382 | 1,241 | 3,623 | 23.4% |
| Nevada | 1,705 | 47 | 156 | 203 | 11.9% |
| New Hampshire | 2,364 | 383 | 358 | 741 | 31.3% |
| New Jersey | 6,448 | 750 | 1,501 | 2,251 | 34.9% |
| New Mexico | 3,850 | 404 | 294 | 698 | 18.1% |
| New York | 17,361 | 2,128 | 4,518 | 6,646 | 38.3% |
| North Carolina | 17,783 | 2,272 | 2,787 | 5,059 | 28.4% |
| North Dakota | 4,458 | 743 | 249 | 992 | 22.3% |
| Ohio | 27,998 | 2,862 | 4,001 | 6,863 | 24.5% |
| Oklahoma | 23,524 | 5,793 | 1,614 | 7,407 | 31.5% |
| Oregon | 7,318 | 514 | 1,155 | 1,669 | 22.8% |
| Pennsylvania | 22,325 | 5,802 | 3,934 | 9,736 | 43.6% |
| Rhode Island | 748 | 164 | 232 | 396 | 52.9% |
| South Carolina | 9,221 | 1,260 | 808 | 2,068 | 22.4% |
| South Dakota | 5,924 | 1,216 | 261 | 1,477 | 24.9% |
| Tennessee | 19,838 | 1,325 | 2,776 | 4,101 | 20.7% |
| Texas | 50,271 | 2,186 | 7,851 | 10,037 | 20.0% |
| Utah | 2,851 | 233 | 254 | 487 | 17.1% |
| Vermont | 2,712 | 500 | 467 | 967 | 35.7% |
| Virginia | 13,417 | 1,208 | 2,234 | 3,442 | 25.7% |
| Washington | 7,651 | 400 | 1,661 | 2,061 | 26.9% |
| West Virginia | 7,001 | 1,058 | 1,515 | 2,573 | 36.8% |
| Wisconsin | 13,798 | 1,302 | 789 | 2,091 | 15.2% |
| Wyoming | 3,030 | 389 | 231 | 620 | 20.5% |
| Puerto Rico | 2,146 | 241 | 822 | 1,063 | 49.5% |
| Totals | 599,766 | 72,524 | 79,792 | 152,316 | 25.4% |
Source: National Bridge inventory, Federal Highway Administration
