150 railroad stations from Vermont to Virginia were part of the operation called "Alerts." It was a coordinated effort by federal, state and local police agencies to increase security on trains and inside stations.
The exercise included the use of dogs trained to detect explosives.
"We have a total of, I believe, 25 police agencies in Pennsylvania working with us. We have Philadelphia P.D., federal air marshals, Secret Service, Amtrak Police, SEPTA and CSX," said Maureen Powers of Amtrack Police.
"It's a great opportunity and an exercise for us to test and assess our skills. But, if we observe behavoir that fall outside the norm, that indicates criminal activity, we're fully able and prepared to respond to it," said Robert Rogers of the Transportation Security Administration.
The potential for problems is great in the northeast where 750,000 people a day ride the rails. The deployed officers provide a high security presence, checking unattended bags, and watching suspicious activity.
One woman said just seeing the police presence made her feel safer.
"It might just be a feeling that I have that I feel more secure, and it might not be more secure, but the feeling itself carries a lot of weight," said Chris Simiriglia of Pitman, N.J.
There have been terrorist attacks on foreign railroads in recent years. There has not been one in the U.S., and the agencies taking part in this exercise hope to keep it that way.