During the October 2024 meeting of the American Bar Association’s Forum on Construction held in Pittsburgh, a city of many bridges, the importance of bridges to our nation’s transportation infrastructure was apparent. Just two years ago, the Forbes Avenue bridge in Pittsburgh collapsed—resulting in several vehicles and a bus falling into a ravine. Ten people were injured in the event. It was later reported that the bridge had received a “poor” rating but was still permitted to remain open to traffic. The event resulted in several lawsuits which, just this past September, the City of Pittsburgh requested $500,000 from the city council to settle. The Forbes Avenue bridge is hardly a unique case and is just one example of the litigation that can ensue if we fail to maintain our aging infrastructure.
The State of Our Nation’s Bridges
As of June 2024, the
United States has more than 616,000 bridges located on public roads, including interstate
highways, U.S. highways, state and county roads, as well as publicly accessible
bridges on federal and tribal lands.
However, according to the
American Society of Civil Engineers’ most recent bridge infrastructure report
card released in 2021, 42% of all U.S. bridges are at least 50 years old, and
46,154, or 7.5%, of the nation’s bridges are considered structurally deficient,
meaning the bridges are in “poor” condition. As ranked by the National Bridge
Inventory, bridges are assigned numerical ratings based upon the conditions of
a bridge’s roadway and structural components. A rating of seven or higher means
that the bridge is in “good” condition, a rating of a five or six means that the
bridge is in “fair” condition and a rating of four or less means that the
bridge is in “poor” condition. A bridge is given an overall rating of “poor” if
any of the bridge structural components is found to be in poor condition which
is weighted by the bridge’s roadway or deck area and annual daily traffic. In
the U.S., 178 million trips are made across structurally deficient bridges
every day.
In recent years, as the
average age of America’s bridges increases to 44 years, the number of bridges classified
as poor based on unweighted bridge count has continued to slowly decline based
upon the nation’s investment in its bridge infrastructure from 10.1% in 2008 to
7.6% in 2018. However, the rate of improvements has slowed and substantial
prolonged investment is required to maintain, improve and rebuild our nation’s
bridges.
A recent estimate of the
nation’s backlog of bridge rehabilitation investment is $191 billion and that annual
spending on bridge rehabilitation needs to increase by 58% or from $14.4
billion annually to $22.7 billion annually to improve the backlog. At the
current rate of investment, it will take until 2071 to make all of the bridge
repairs that are currently necessary. At the current rates of aging and
replacement, almost half of the nation’s bridges will require major structural
investments within the next 15 years.
Accelerated Bridge Construction
As the rehabilitation and
repair of the nation’s aging bridges continues to be a priority, the Federal
Highway Administration (FHWA) has been at the forefront of promoting the use of
accelerated bridge construction techniques and pre-fabricated bridge elements
in bridge rehabilitation and construction projects. Accelerated bridge
construction (ABC), or “rapid bridge replacement,” is a bridge construction
process that relies on advanced technology, project planning and design,
innovative materials, smarter procurement, and new construction methods to
reduce the time and effort it takes to replace or rehabilitate bridges.
As a result, state
departments of transportation have begun to turn to accelerated bridge
construction as a solution for upgrading substandard bridges. State departments
of transportation have used ABC techniques to reduce total bridge construction delivery
time, realize cost savings, reduce closure time, minimize loss of toll
revenues, improve the durability of bridge elements, reduce traffic impacts and
long detours, minimize costly use of temporary structures and remote site
locations, reduce onsite construction time and weather-related time delays, diminish
impacts to the traveling public and road workers to construction work zones and
decrease environmental impacts.
Some Best Practices in Accelerated Bridge
Construction
Since bridges constructed
using ABC methods use prefabricated components built offsite, including utility
components, decks, piers, columns, foundations and piles, the number of various
prefabricated components should be kept to a minimum. The prefabricated components should also be
repetitive for the same project and relatively easy to transport and install. Early
engagement of third-party stakeholders, including railroads, utility companies,
and the traveling public, is necessary to create open communications and
information sharing that will help influence the aggressive project schedule
for an ABC project. Stringent quality assurance procedures should be
implemented and stress monitoring should be used to monitor bridge movement
during installation. Prequalified list of materials and products should be
maintained for incorporation into ABC projects. Certified fabrication plants
and certified contractors should be used for fabrication and installation of
bridge elements. In addition, due to the accelerated pace of construction, processes
should be implemented to reduce worker fatigue including rotation of shifts,
increased crew size, and frequent breaks.
Accelerated Bridge
Construction “Slide-In” Bridge 3D Animation
Slide-in bridge
construction or “lateral slide” is an ABC
technology promoted by the FHWA Every Day
Counts program. The program is an initiative undertaken by
the FHWA to bring new technologies to infrastructure construction driven by the
desire to reduce impacts to the traveling public. The rehabilitation of a
bridge using lateral slide technology is effectively demonstrated in the 3D animation
produced by the Pennsylvania Turnpike Authority entitled “How Accelerated Bridge
Construction works on the PA Turnpike.”
Conclusion
As our nation’s bridge
infrastructure continues to age and deteriorate, substantial additional federal
and state investment in building, repairing and modernizing our nation’s bridges
is required to ensure America’s bridges are safe and operational, meet current
and future traveler needs, support local economies and strengthen supply chains.
The Bipartisan Infrastructure Law, which established the Bridge Investment
Program, dedicates $40 billion over five years to tackle the backlog of bridge
projects. Under the program, more than 11,000 bridges are being rebuilt,
repaired or modernized. As of October 2024, the Bridge Investment Program has
invested $8.1 billion into 100 bridge projects in 44 states across the country and
an additional $21 billion in dedicated bridge formula funds used to distribute funding
to states for highway bridge repairs and upgrades. Given the bridge repair
backlog of $191 billion, additional substantial and long term federal and state
investment is required to maintain the integrity of the nation’s bridges.
Sources:
National
Bridge Inventory – U.S. Department of Transportation - Bureau of Transportation
Statistics
American
Society of Civil Engineers’ Bridge Infrastructure Report Card (2021)
Accelerated
Construction - Construction Strategies - FHWA Work Zone
Accelerated
Bridge Construction: Best Practices and Techniques
