With the revelation that al Qaeda was considering targeting U.S. rail lines, transportation officials and experts are concerned that enough is being done to ensure that train travel is safe.
Sen. Charles Schumer of New York said today that there should even be a "do not ride" list for Amtrak, similar to the no-fly lists that are part of the airline security effort.
Train bombings overseas, such as occurred in Madrid and London, are eveidence of what terrorists are capable of, but the documents found in the raid last week on Osama bin Laden's compound indicated that the more likely mode of attack would be on the rails themselves, rather than a terrorist trying to get on a train with a bomb.
By tampering with the rails, the intelligence indicated, al Qaeda was hoping to send a whole train tumbling off a bridge or into a valley.
"The targeting of the railroad infrastructure itself is a much smarter move on the part of the terrorists, because you get more bang for the buck," said Kevin Lynch, a retired freight rail police chief who consults on railroad police practices.
With so much of the train lines running through the wide open spaces in this country, there could be attractive terrorist targets. Forty percent of the rail lines in the United States have no automatic monitoring systems. Those lines are supposed to be inspected at least twice a week, but that still can leave long stretches of track unwatched for long stretches of time.
"You could disrupt the rail network and disrupt commerce across the country," Lynch said.
There are 140,000 miles of freight and passenger track in the United States, not counting subway systems and light rail, as well as 3,100 train and transit stations. There were more than 4 billion passenger rail trips last year from commuters rushing to work, students heading to school and families out on vacation.
On any one day, 78,000 people ride Amtrak, 660,000 step on the elevated trains in Chicago, and 8 million ride the New York City subway system.
The rail lines along Amtrak's heavily traveled Northeast Corridor from Washington, D.C., to New York, the lines are carefully inspected.
"These guys out here, yeah workers out here, every day walk every mile of the railroad," Amtrak engineer Jack Barton said.
"We have people out on the Northeast Corridor tracks every day," Amtrak spokesman Steve Kulm told ABC News, but he said "they are not necessarily inspecting every mile of track, every day."
Workers also inspect and maintain bridges and electrical power substations, overhead wires and stations and signal systems, and drainage ditches, he said.
In recent years, anti-terror deterrents have been introduced, such as additional bomb detection equipment and new vapor wake detection dogs trained to smell every possible component of explosives, which the Department of Transportation announced in late October.
As a result of what appears to be an already employee strapped system, adding trained K-9's could make sense. According to Bureau of Labor statistics, there are fewer than 1,000 officers policing rail transportation in the United States.
A most recent record to step up the nation's rail security was seen in July when Department of Homeland Security (DHS) Secretary Janet Napolitano launched the first phase of the agency's "See Something, Say Something" campaign, requesting the public play a role in pointing out potential railway threats.
The effort is part of a series of events called Operation Rail Safe, which includes local, state, and federal efforts to increase occasional security presence onboard trains, canine sweeps and random passenger bag inspections at unannounced locations.
Lynch, however, said he is not convinced.
"Most of the time the railroad is unprotected, hundreds and hundreds of miles at a stretch," he said.
Nevertheless, officials are promising heightened vigilance.