French Train Attack a Reminder of US Railroad Vulnerability

Amtrak is reassuring commuters after the scary incident on a Paris-bound train.

— -- Days after three Americans subdued an AK-47-wielding gunman on a Paris-bound commuter train, Amtrak, one of America’s largest passenger rail companies, is reassuring travelers in the states that the carrier is taking security seriously.

The security initiatives are ongoing and not in reaction to Friday’s attack, the partially government-funded railroad said.

But the reality is that, like airlines, U.S. railroads remain vulnerable to terrorist attacks, experts say.

“The increased security efforts around air travel have led to concerns that terrorists may turn their attention to ‘softer’ targets, such as transit or passenger rail,” a March 2015 report from the Congressional Research Service reads.

“A key challenge Congress faces is balancing the desire for increased rail passenger security with the efficient functioning of transit systems.”

With rail passengers coming and going rapidly throughout the day, establishing airport-style security protocols at train stations “would essentially make rail travel extraordinarily difficult if not impossible,” said John Cohen, a former U.S. counterterrorism official and ABC News contributor.

Added ABC News contributor and former FBI agent Brad Garrett: “The idea that you could screen all of those people is not realistic.”

Instead, rail security teams are focused on gathering intelligence to protect critical stations, tunnels, and bridges and maintaining highly visible deterrence teams, including a robust uniformed police presence.

Amtrak retains its own police force with over 500 personnel, including canine units that “provide a psychological and physical deterrent to potential threats,” plus two analysts with top secret security clearance who routinely sit in on classified briefings with federal officials and coordinate VIP movements, according to the Amtrak Police Department.

And armed Amtrak security personnel perform random luggage searches at bustling hubs like Washington’s Union Station or New York’s Penn Station.

And yet, "notwithstanding all that we do from a rail security prospective,” Cohen said, “chances are that if someone wanted to get on a train with a firearm and begin shooting people, there's a pretty good chance that they would be able to do it.”

ABC News’ Emily Shapiro contributed to this report.