The Brooklyn Bridge falls within the accepted threshold for the risk of collapsing from a bridge strike in a given year, according to a recent calculation from the New York City Department of Transportation. The calculation follows the naming of the bridge by the National Transportation Safety Board in March among 68 bridges they recommended owners calculate a previously unknown risk of collapse due to vessel strikes, also called AF or "annual frequency." The AF is calculated as the risk in any given year. It takes into account the ship's characteristics, speeds, loading characteristics, waterway geometry, water depth, conditions, bridge geometry, pier protections and maximum horizontal load a pier can handle. All bridges built over navigable waterways are now required to have an annual probability of the event occurring less than 1 in 1,000 for “typical” bridges and 1 in 10,000 if it's classified as a “critical” bridge that’s an important link in the highway system. This is equivalent to a collision resulting in a bridge collapse occurring once every 1,000 or 10,000 years."A bridge design with a risk level below the acceptable threshold would minimize the risk of a collapse but does not guarantee that a collapse from a vessel collision will not occur. Likewise, a risk level above the acceptable threshold does not mean a collapse from a vessel collision is a certainty," the March report from the NTSB said. The NTSB report was released around the one-year anniversary of the collapse of the Francis Scott Key Bridge in Baltimore, where a cargo ship struck the bridge after losing power. While guidance on how much risk is acceptable exists now, it didn’t until the American Association of State Highway and Transportation Officials issued it in 1991 as a result of a ship collision with the Sunshine Skyway Bridge in Florida in 1980.The top of the masts of a tall ship struck the Brooklyn Bridge in New York City on Saturday night, killing two crew members and injuring several others.The vessel that collided with the bridge, the Cuauhtémoc, is a Mexican Navy ship that stopped in Brooklyn as a part of a global tour. It departed a pier to head toward the ocean to sail to Iceland, but instead went in the direction of the Brooklyn Bridge.It’s nearly 300 feet long — less than a third of the Dali cargo ship that struck the Francis Scott Key Bridge in Baltimore more than a year ago — and 160 feet tall. An initial report says that the ship's pilot lost power from a mechanical problem, New York Police Department Special Operations Chief Wilson Aramboles said to the Associated Press, but information is preliminary. The Dali had lost power prior to striking the Key Bridge. The Brooklyn Bridge was one of 13 bridges in New York that showed up in the NTSB report — the most bridges of any state. The New York City Department of Transportation owns three of the bridges on the list: the Brooklyn Bridge, Manhattan Bridge and the Williamsburg Bridge.There has been at least one other occurrence in the past three years in which the Brooklyn Bridge was struck.In July 2023, a crane aboard a barge made contact with the bottom of the bridge while moving north, according to a U.S. Coast Guard investigation activity report. The investigation concluded that the ship’s master incorrectly calculated the crane’s height.The collision led to damage on the bottom of the bridge but did not affect the bridge’s structural integrity, the report said. What is known about the risk of bridge collapses from ship strikes? The calculation of the combined likelihood of a ship strike causing a bridge to collapse is up to individual owners to find out because of the number of factors involved, but researchers at Johns Hopkins were able to identify which are simply at risk of a strike for a large vessel. Large vessels are defined as being 492 feet or longer, or than half the length of the Dali. Some of the same bridges named in the NTSB report were also shown to be at risk of large ship collision, according to researchers at Johns Hopkins University. The findings, also released in March, show one bridge has the likelihood of being struck by a large ship in as little as once every 17 years. While Hopkins was able to calculate the risk of large ship strikes for the busiest bridges in the U.S., going further requires extra detail — something that the NTSB recommended each bridge owner do themselves. After the NTSB made its recommendation to the owners of the 68 bridges in 19 states, nearly all have initially replied to the NTSB either saying they are working on calculating the risk or had done so, according to emails between bridge owners and the NTSB. The NTSB research formula took into account both vessel traffic and pier protection — something that has to be done for each bridge individually."Calculating a bridge’s AF can help owners understand their bridges’ vulnerability of collapse from a vessel collision and the aspects of bridge design or vessel traffic that contribute to this vulnerability, especially for bridges with an AF above the AASHTO threshold," the March report from the NTSB said. The New York City Department of Transportation's three bridges, including the Brooklyn, were all below the threshold. PHNjcmlwdCB0eXBlPSJ0ZXh0L2phdmFzY3JpcHQiPiFmdW5jdGlvbigpeyJ1c2Ugc3RyaWN0Ijt3aW5kb3cuYWRkRXZlbnRMaXN0ZW5lcigibWVzc2FnZSIsKGZ1bmN0aW9uKGUpe2lmKHZvaWQgMCE9PWUuZGF0YVsiZGF0YXdyYXBwZXItaGVpZ2h0Il0pe3ZhciB0PWRvY3VtZW50LnF1ZXJ5U2VsZWN0b3JBbGwoImlmcmFtZSIpO2Zvcih2YXIgYSBpbiBlLmRhdGFbImRhdGF3cmFwcGVyLWhlaWdodCJdKWZvcih2YXIgcj0wO3I8dC5sZW5ndGg7cisrKXtpZih0W3JdLmNvbnRlbnRXaW5kb3c9PT1lLnNvdXJjZSl0W3JdLnN0eWxlLmhlaWdodD1lLmRhdGFbImRhdGF3cmFwcGVyLWhlaWdodCJdW2FdKyJweCJ9fX0pKX0oKTs8L3NjcmlwdD4=
The Brooklyn Bridge falls within the accepted threshold for the risk of collapsing from a bridge strike in a given year, according to a recent calculation from the New York City Department of Transportation.
The calculation follows the naming of the bridge by the National Transportation Safety Board in March among 68 bridges they recommended owners calculate a previously unknown risk of collapse due to vessel strikes, also called AF or "annual frequency."
The AF is calculated as the risk in any given year. It takes into account the ship's characteristics, speeds, loading characteristics, waterway geometry, water depth, conditions, bridge geometry, pier protections and maximum horizontal load a pier can handle.
All bridges built over navigable waterways are now required to have an annual probability of the event occurring less than 1 in 1,000 for “typical” bridges and 1 in 10,000 if it's classified as a “critical” bridge that’s an important link in the highway system. This is equivalent to a collision resulting in a bridge collapse occurring once every 1,000 or 10,000 years.
"A bridge design with a risk level below the acceptable threshold would minimize the risk of a collapse but does not guarantee that a collapse from a vessel collision will not occur. Likewise, a risk level above the acceptable threshold does not mean a collapse from a vessel collision is a certainty," the March report from the NTSB said. The was released around the one-year anniversary of the collapse of the Francis Scott Key Bridge in Baltimore, where a cargo ship struck the bridge after losing power.
While guidance on how much risk is acceptable exists now, it didn’t until the American Association of State Highway and Transportation Officials issued it in 1991 as a result of a ship collision with the Sunshine Skyway Bridge in Florida in 1980.
The top of the masts of a tall ship struck the Brooklyn Bridge in New York City on Saturday night, killing two crew members and injuring several others.
The vessel that collided with the bridge, the Cuauhtémoc, is a Mexican Navy ship that stopped in Brooklyn as a part of a global tour. It departed a pier to head toward the ocean to sail to Iceland, but instead went in the direction of the Brooklyn Bridge.
It’s nearly 300 feet long — less than a third of the Dali cargo ship that struck the Francis Scott Key Bridge in Baltimore more than a year ago — and 160 feet tall.
An initial report says that the ship's pilot lost power from a mechanical problem, New York Police Department Special Operations Chief Wilson Aramboles said to the Associated Press, but information is preliminary. The prior to striking the Key Bridge.
The Brooklyn Bridge was one of 13 bridges in New York that showed up in the NTSB report — the most bridges of any state.
The New York City Department of Transportation owns three of the bridges on the list: the Brooklyn Bridge, Manhattan Bridge and the Williamsburg Bridge.
There has been at least one other occurrence in the past three years in which the Brooklyn Bridge was struck.
In July 2023, a crane aboard a barge made contact with the bottom of the bridge while moving north, according to a . The investigation concluded that the ship’s master incorrectly calculated the crane’s height.
The collision led to damage on the bottom of the bridge but did not affect the bridge’s structural integrity, the report said.
What is known about the risk of bridge collapses from ship strikes?
The calculation of the combined likelihood of a ship strike causing a bridge to collapse is up to individual owners to find out because of the number of factors involved, but researchers at Johns Hopkins were able to identify which are simply at risk of a strike for a large vessel. Large vessels are defined as being 492 feet or longer, or than half the length of the Dali.
Some of the same bridges named in the NTSB report were also shown to be at risk of large ship collision, according to researchers at Johns Hopkins University.
The findings, also released in March, show one bridge has the likelihood of being struck by a large ship in as little as once every 17 years.
While Hopkins was able to calculate the risk of large ship strikes for the busiest bridges in the U.S., going further requires extra detail — something that the NTSB recommended each bridge owner do themselves.
After the NTSB made its recommendation to the owners of the 68 bridges in 19 states, nearly all have initially replied to the NTSB either saying they are working on calculating the risk or had done so, according to emails between bridge owners and the NTSB.
The NTSB research formula took into account both vessel traffic and pier protection — something that has to be done for each bridge individually.
"Calculating a bridge’s AF can help owners understand their bridges’ vulnerability of collapse from a vessel collision and the aspects of bridge design or vessel traffic that contribute to this vulnerability, especially for bridges with an AF above the AASHTO threshold," the March report from the NTSB said.
The New York City Department of Transportation's three bridges, including the Brooklyn, were all below the threshold.
