According to authorities, documents uncovered in the recent raid that killed al Qaida leader Osama bin Laden show that the terror group may have been plotting to launch an attack on the U.S. by derailing a passenger train.
In response, transit systems across the nation are operating under a heightened sense of awareness.
The Chicago Transit Authority (CTA), for example, is reminding employees and passengers to be on the lookout for anything suspicious.
"The CTA is in touch with the appropriate local and federal agencies to stay informed of any developments that could affect or impact bus and rail service. Earlier this week, the CTA reissued security bulletins, reminding employees of what activities to look for and what steps to take should they observe any suspicious or criminal activity during the course of their duties. We also continue to make announcements reminding our customers that vigilance and awareness of their surroundings is an important part of our efforts and encourage them to report any unusual or suspicious activity to 911 or to CTA personnel," the CTA said in a statement.
Sen. Charles Schumer (D-NY) is even calling for a "no-ride" list for Amtrak trains in an effort boost rail security measures.
While news that al Qaida may have been plotting an attack on passenger trains may come as a shock to some, Kenneth Cummins, chief security officer for Sound Transit, the transit authority for the Puget Sound region of Washington, said that the industry has known for sometime that it is a big target for terrorists.
"To be honest, the news last week wasn't a surprise. We've known for many years that rail was a target," Cummins said. "Just looking at incidents around the world, public transit is usually pretty high on the terrorist target list. We've always kind of assumed that it wasn't a matter of if, but when?"
Though he isn't shocked by the newly uncovered plot, Cummins said that Sound Transit, which operates three rail lines and has an average daily ridership of 25,000 passengers, did increase its security presence following news of bin Laden's death out of concern over the threat of a retaliatory attack.
"On the public side, this information coming to light has kind of rejuvenated interest in how secure our transit (systems) is and it's just good to keep the public aware of things like this," Cummins explained.
Cummins said his primary focus when it comes to terrorism is explosive devices, followed closely by Mumbai-style coordinated gunmen attacks. Though chemical and biological attacks are a concern, Cummins indicated that since most of the Sound Transit system is open air, it's not as great a concern as it would be for some subway systems along the East Coast. When it comes to tampering with rail lines, Cummins said there are also numerous security measures in place to protect against derailments.
"With the BNSF lines and our heavy freight rail and our light rail, there is so much traffic on those systems that it would be hard to actually tamper with the rail during the day. Also, there are systems on those lines that will notify us if the rail has been cut or if there is a heavy enough object to block the track," he said. "Our primary concern then is somebody tampering with the rail afterhours before service begins."
To guard against afterhours tampering, Cummins said that before passenger rail service begins every morning that the first train out carries no passengers and they conduct a sweep that covers "every inch" of the track both north and southbound to look for damaged rail or objects that may be in the way.
"We also have security and law enforcement 24/7," he said. "We have patrols of major intersections and critical infrastructures such as our bridges, overpasses and traction power substations, those critical nodes that would affect the system if one were damaged or destroyed or tampered with."
In a way, Cummins said that when plots like these are uncovered they serve as validation for the security measures that have been put in place over the years.