The National Transportation Safety Board recommended Thursday that 68 bridges across 19 states undergo a vulnerability assessment to determine their risk of bridge collapse from a vessel collision, as the agency continues its investigation into the March 2024 collapse of the Francis Scott Key Bridge in Baltimore.
Some 30 bridge operators, such as state agencies and port authorities, urgently need to assess the “risk of catastrophic collapse” of their spans from allision by large vessels like the 984’ containership Dali that hit the Key bridge, said NTSB chair Jennifer Homendy.
“We need action. Public safety depends on it,” Homendy said during a news media briefing.
A methodology for calculating the risk was published by state highway and transportation experts in 1991, in response then to the NTSB’s investigation of the 1980 Sunshine Skyway Bridge collapse in Florida.
The Key bridge opened in 1977, before the Federal Highway Administration began to require new allision risk calculations Had the Maryland Transportation Authority used them, Maryland highway officials could have seen the Key bridge was at 30 times the acceptable risk threshold recommended In 1991, said Homendy.
That 1991 guidance was established by the American Association of State Highway and Transportation Officials, or AASHTO.
“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,” according to a summary released by the NTSB. “The recommendations are issued to bridge owners to calculate the annual frequency of collapse for their bridges using AASHTO’s Method II calculation.”
The agency is recommending 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.”
In 1991, AASHTO had recommended that all bridge owners conduct the vulnerability assessment on existing bridges to evaluate their risk of catastrophic collapse in the event of a vessel collision – and reiterated that recommendation to state agencies again in 2009.
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.”
“As of October 2024, they still haven’t (performed the calculations) o the Chesapeake Bay Bridge,” said Homendy.
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 agency released more than 1,000 pages of its Marine Investigation Report , a work in progress with new updates expected the coming days, said Homendy. A final report will be completed this fall, she said.
