With its focus on air travel, U.S. trains vulnerable to terrorist attack, experts say

(Source: New York Times, December 11, 2015)

WASHINGTON, D.C. — The day before Thanksgiving, with the country on high alert for terrorist threats, dozens of armed guards from the Department of Homeland Security and local law enforcement patrolled Union Station here as hundreds of passengers emerged from commuter and Amtrak trains.

Full story: New York Times