BALTIMORE’s Frances Key Bridge, which collapsed after being struck by the containership Dali a year ago on Friday, was almost 30 times above the acceptable risk threshold for critical or essential bridges, according to guidance established by the American Association of State Highway and Transportation Officials.
The US National Transportation Safety Board late last week recommended that 30 owners of 68 bridges across 19 states conduct a vulnerability assessment to determine the risk of bridge collapse from a vessel collision, part of the ongoing investigation into the collapse of the Baltimore bridge.
Over the last year, the NTSB identified 68 bridges that were designed before the AASHTO guidance was established — like the Key Bridge — that do not have a current vulnerability assessment. The recommendations are issued to bridge owners to calculate the annual frequency of collapse for their bridges using AASHTO’s Method II calculation.
The report does not suggest that the 68 bridges are certain to collapse but the Board is recommending that these 30 bridge owners evaluate whether the bridges are above the AASHTO acceptable level of risk. The NTSB recommended that bridge owners develop and implement a comprehensive risk reduction plan, if the calculations indicate a bridge has a risk level above the AASHTO threshold.
Since 1994, the Federal Highway Administration, or FHWA, has required new bridges be designed to minimize the risk of a catastrophic bridge collapse from a vessel collision, given the size, speed and other characteristics of vessels navigating the channel under the bridge. The Key Bridge was built before vulnerability assessments were required by FHWA.
The NTSB found that had the Maryland Transportation Authority, or MDTA, conducted a vulnerability assessment on the Key Bridge based on recent vessel traffic, MDTA would have been aware that the Key Bridge was above the acceptable risk and would have had information to proactively reduce the bridge’s risk of a collapse and loss of lives associated with a vessel collision with the bridge.
The NTSB is also recommending FHWA, the U.S. Coast Guard and the U.S. Army Corps of Engineers establish
an interdisciplinary team to provide guidance and assistance to bridge owners on evaluating and reducing the risk, which could mean infrastructure improvements or operational changes.
The Maersk-chartered, Singapore-owned-and managed 9,962 TEU Dali was departing Baltimore for Colombo on 28 March 2024 when it lost electrical power and propulsion and struck the southern pier supporting the central truss spans of the Francis Scott Key Bridge, which subsequently collapsed. Six construction crewmembers were killed and another was injured, as well as one person onboard the vessel.
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