It was a two-sentence email, hastily fired off the morning after the Key Bridge collapsed from one structural engineer to another, that started off an 11-month long inquiry. Johns Hopkins Civil Engineer Michael Shields and his t eam of students and fellow professors wanted to know: was the collapse of the Key Bridge a freak accident, or something that's likely to happen again? And are other US bridges at risk?For the last year, theyve been studying how likely it is for a ship to crash into bridges in the United States. Sifting through hundreds of millions of data points from all 50 ports and some 80,000 bridges in the National Bridge Inventory.They found the risk of a ship collision for many bridges is a lot higher than anyone would want it to be. "We can confirm now with these numbers that this was not a rare event. This is something that we could've seen coming. But we had somewhat of a blind spot to it," explains Michael Shields, a Johns Hopkins Department of Civil and Systems Engineering professor.Their calculations predicted a ship would strike the Key Bridge within the first 48 years of its existence. The bridge had just turned 47-years-old a few days before it collapsed. RELATED STORY | US bridges are frequently struck by ships and bargesOther bridges, like the Huey P. Long Bridge in Louisiana and the Bay Bridge in San Francisco, are even more vulnerable: a ship collision can be predicted to happen every 20 or so years. And since researchers looked at ports that see big ships pass through, these collisions would be strong enough to cause catastrophic damage or a full collapse. Shields said the results are concerning, only if we don't do anything about them."If we don't do anything about it, this will happen again," Shields told the Scripps News Group's Elizabeth Worthington. "And it won't be a century before it happens again. It will be a matter of years, or maybe a decade or so before it happens again."WATCH | Many U.S. bridges at concerning risk of ship collision, according to Johns Hopkins engineers Johns Hopkins engineers find concerning risk of ship collision for many U.S. bridgesAccording to modern bridge design standards, the annual chances of a bridge collapse from a ship collision should be less than 1 in 10,000. However, those standards didnt formally exist until 1994, inspired by the collapse of the Sunshine Skyway Bridge in Florida in 1980. Unsurprisingly, nearly all of the at-risk bridges identified by the Hopkins team have just one thing in common: they were built before 1994.So the Key Bridge, the Chesapeake Bay Bridge, the Oakland Bay Bridge, these bridges were never designed for a ship collision in the first place. When they changed the design provisions, they did not require that existing bridges be retrofitted and protected for these types of events," Shields explains. But they can be. The Scripps News Group visited the Delaware Memorial Bridge last year to learn about the $92 million protection system the state is installing on the 1950s-era bridge - a major investment, but one that pales in comparison to the nearly $2 billion price tag projected for the new Key Bridge. "This is an opportunity for us to open our eyes to a real vulnerability, to a real risk to our infrastructure," Shields said. RELATED STORY | One year after Baltimore disaster, bridges are only getting worseThat includes the Chesapeake Bay Bridge. The researchers found a collision is expected there once every 86 years. The bridge is 73-years-old. For those who are already not fond of driving over that bridge, Shields can offer a comforting thought."You have to also think about yourself as an individual commuter and saying, the chances that that event - that might happen some time in the next few decades - will happen at the moment that I am on that bridge is still incredibly small," Shields told the Scripps News Group. "I, for one, would not hesitate to drive over that bridge."Last week, the National Transportation Safety Board (NTSB) put out urgent safety recommendations for 68 bridges in 19 states. The owners of these bridges failed to conduct a vulnerability assessment that was recommended by the American Association of State Highway and Transportation Officials (AASHTO) after the Sunshine Skyway Bridge collapse. The assessment would have informed the bridge owners what the risk of a collapse from a ship collision was for their bridge. According to the NTSB, the Maryland Transportation Authority (MDTA) never conducted the assessment for the Key Bridge or the Bay Bridge. The MDTA says one is currently underway for the Bay Bridge.The list of bridges identified to be most at-risk of a ship collision by the Hopkins team is below. It is consistent with the NTSB's list of bridges that have never had a vulnerability assessment, except for the Oakland Bay Bridge, because the NTSB confirmed that it's currently in the design phase for new protective systems. Huey P. Long Bridge, Louisiana: Collision expected once every 17 years. San FranciscoOakland Bay Bridge: Collision expected once every 22 years. Crescent City Connection, New Orleans: Collision expected once every 34 years. Beltway 8 Bridge, Texas: Collision expected once every 35 years. Hale Boggs Memorial Bridge, Louisiana: Collision expected once every 37 years. Bayonne Bridge, N.Y./N.J.: Collision expected once every 43 years. Fred Hartman Bridge, Texas: Collision expected once every 47 years. Martin Luther King Bridge, Texas: Collision expected once every 64 years. Sunshine Bridge, Louisiana: Collision expected once every 71 years. Rainbow Bridge, Texas: Collision expected once every 71 years. Veterans Memorial Bridge, Louisiana: Collision expected once every 74 years. Chesapeake Bay Bridge, Maryland: Collision expected once every 86 years. Talmadge Memorial Bridge, Georgia: Collision expected once every 88 years. Veterans Memorial Bridge, Texas: Collision expected once every 94 years. Delaware Memorial Bridge, Del./N.J.: Collision expected once every 129 years. Dames Point Bridge, Florida: Collision expected once every 152 years. Horace Wilkinson Bridge, Louisiana: Collision expected once every 198 years. Verrazzano-Narrows Bridge, New York: Collision expected once every 362 years. Golden Gate Bridge, California: Collision expected once every 481 years. John A. Blatnik Bridge, Minnesota/Wisconsin: Collision expected once every 634 years.You can learn more about the Hopkins study and the researchers' methodology here. This story was originally published by Elizabeth Worthington with the Scripps News Group. ...read more read less