I wrote early this morning on my tumblr blog about what I observed at Union Station prior to 6:30 a.m. today

WBAL and the AP have more information:

Rail passengers from Virginia to Vermont were greeted by a heavy police presence Tuesday morning, as Amtrak, the Transportation Security Administration and local agencies teamed up for a joint show of force.

Officials say the rush-hour deployment along the Northeast Corridor was meant to demonstrate ongoing collaboration and to give local officials a chance to familiarize themselves with the stations.

The railroad and the TSA say officers from about 100 commuter rail, state, and local police agencies took part in the operation, which included random passenger bag inspections.

The exercise was not announced beforehand. Amtrak and the TSA say similar exercises will be held in the future around the country.