Trains can't be used by terrorists to run into large buildings. But then, as the bombings of commuter trains in Spain showed, terrorists will target any place with large groups of people. And trains, because they're so open and often crowded, are particularly vulnerable.
The Department of Homeland Security (DHS) has already told train travelers to be on the lookout for unattended baggage or suspicious activity. And local rail agencies have been advised to increase the number of officers at stations, deploy more explosive-detection teams, and in some cases, put police on trains.
Some 32 million people travel by train each day in the US, including subways. Screening both bags and passengers on trains would be much more difficult than it has been for airline travel since 9/11.
The various levels of government must carefully weigh the risks against the costs of preventing an attack on the rails. (In rail-dependent New York City, Mayor Michael Bloomberg said "the chance of a terrorist doing damage to you is a lot less than you getting hit by lightning.")
One bill just introduced by three senators on Capitol Hill would give the DHS six months to assess risk on the nation's rails and report back to Congress. And it would also provide $1.29 billion for security-based improvements, especially in rail tunnels in the Northeast. Despite $12 billion spent to secure the nation's airlines since 9/11, only $115 million in grants to local transit and rail agencies have been handed out since May 2003.
The financial and physical challenge of securing crowded and often security-porous train stations can seem daunting. Total security is unlikely, as Asa Hutchison, Homeland Security Department's undersecretary for border and transportation security, points out.
The best defense is a riding public watching for signs of trouble and alerting officials. Other sensible steps, include bomb-proofing trash bins and using bomb- and chemical-detection equipment.
In the politically charged atmosphere of an election, Congress must resist the pressure for knee-jerk spending on rail security or use the heightened concerns simply for pork-barrel spending. A thorough and balanced reassessment is needed first.
The Madrid attacks were not the first signal for action. In 2002, the FBI issued this bulletin: "Information from debriefing Al Qaeda detainees indicates the group has considered directly targeting US passenger trains."
That's a wake-up call for anyone who rides the rails to remain vigilant, and for rail riding to be made safer.