St. Petersburg's Sunshine Skyway Bridge, Florida's tallest bridge, has been identified by the National Transportation Safety Board as one of 68 bridges that have an "unknown level of risk of collapse" if they were hit by a vessel. The current Skyway Bridge is the second integration — the first one collapsed in 1980 when a freighter hit one of its columns during a thunderstorm. Thirty-five people were killed when six vehicles and a Greyhound bus fell into the water. The NTSB released a report titled 'Safeguarding Bridges from Vessel Strikes: Need for Vulnerability Assessment and Risk Reduction Strategies' on Tuesday. The report says the board identified the need to safeguard bridges from vessel strikes as part of an ongoing investigation launched after the collapse of the Francis Scott Key Bridge in Baltimore after it was hit by a container ship. In its investigation, NTSB determined that the Francis Scott Key was above the level of risk of collapse were it hit by a vessel, a standard established by the American Association for State Highway and Transportation Officials (AASHTO). In the new report, NTSB has identified 68 other bridges that are frequented by ocean-going vehicles and were constructed before the AASHTO guidance was released in 1991. These bridges have not undergone a vulnerability assessment factoring in the most up-to-date information on vessel traffic near the bridge. The NTSB says these bridges have an "unknown level of risk of collapse from a vessel collision." This list includes the "new" Sunshine Skyway, which was completed in 1987. The agency is also urging the owners of the bridges identified to calculate the probability that they will collapse if hit by a vessel using the risk threshold established by the AASHTO.