As part of the ongoing investigation into the collapse last year of the Francis Scott Key Bridge in Baltimore after contact with a containership, the National Transportation Safety Board (NTSB) recently recommended risk assessments for dozens of other bridges around the country.
Specifically, NTSB’s March 18 report calls on 30 owners of 68 bridges across 19 states to conduct a vulnerability assessment to determine the risk of bridge collapse from a vessel collision.
The report does not suggest that the 68 bridges are certain to collapse, says the NTSB, which is recommending that the 30 bridge owners evaluate whether the bridges are above the acceptable level of risk set by the American Association of State Highway and Transportation Officials (AASHTO).
If the calculations indicate a bridge has a risk level above the AASHTO threshold, then the NTSB urges owners of bridges over navigable waterways frequented by ocean-going vessels, the Federal Highway Administration (FHWA), the U.S. Coast Guard (USCG), and the U.S. Army Corps of Engineers (USACE) to act on the safety recommendations in the report, and to develop and implement a comprehensive risk reduction plan.
The NTSB found that the Key Bridge, which collapsed after being struck by the containership Dali on March 26, 2024, was almost 30 times above AASHTO’s acceptable risk threshold for critical or essential bridges.
The Dali, a 984-foot Singapore-flagged cargo vessel, was transiting out of Baltimore Harbor when it experienced a loss of 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 crew members were killed and another was injured, as well as one person onboard the vessel, according to the NTSB.
During the last year, the NTSB identified 68 bridges that were designed before the AASHTO guidance was established in 1991 — like the Key Bridge — that do not have a current vulnerability assessment.
Since 1994, 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 if the Maryland Transportation Authority (MDTA) had conducted a vulnerability assessment on the Key Bridge based on recent vessel traffic, then 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 also recommends that FHWA, USCG, and USACE 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.