WASHINGTON, D.C. — Following an analysis of the National Counterterrorism Center's incident database and interviews with Congress, federal security officials, transit authorities, rail operators, independent security experts and passengers, a USA Today investigation found that the nation's rail network of more than 3,200 stations and 20,000 miles of track combined with the impracticality and cost of screening every passenger leave U.S. subways and rails exposed to the types of terrorist attacks 22 other nations have experienced the last five years. For the full story, click here.