I rode back and forth between Philly and New York this weekend. Despite articles like this- 3 days after the Madrid bombing- security has not noticeably tightened on the North East Corridor.
Both Penn Station and 30th Street had the usual limited police presence. Bomb sniffing dogs were MIA. A passenger can easily stroll down to the platforms without anyone checking tickets or IDs. 30th Street Station and the lower concourse of Penn Station have no security and provide unauthorized access to the tracks. AMTRAK travelers are getting on and off at tiny deserted stations like Metropark and Paoli. Everyone has luggage. There is nothing stopping one of those bags from containing an explosive.
I don't see anything stopping the Madrid nightmare from happening here. Homeland security has forced CAPPS, baggage screening and repeated ID checks for air travel. AMTRAK has nothing. The automated AMTRAK ticketing machines would surely allow purchasing of a ticket with a stolen credit card. Identification and baggage are never checked. Passengers in Philly are on the track platforms long before the trains arrive. It's scary. I don't know how they think our passenger rail system is more secure than Spain's.