Report warns of bioterror attack on public transportation

A USA Today examination has found that, despite the government's attempts to upgrade rail and subway defenses against terrorist attacks, there are major holes in the public transportation system that may be impossible to fix.

These security holes may leave over four billion passengers vulnerable, whereas the tighter security at airports affects fewer than 700 million people. There have been six terrorist plots that have targeted the U.S. rail and subway systems since the September 11, 2001, terrorist attacks, USA Today reports.

"Mass transit systems are much less secure than the aviation sector or certain key government buildings," Clark Kent Ervin, the former inspector general of the Department of Homeland Security, said, according to USA Today.

The Transportation Security Administration has mostly given the responsibility of rail security to local governments, which USA Today said does not have the money and capabilities to make systems secure.

"We know that some terrorist groups see rail and subways as being more vulnerable, because there's not the type of screening that you find in aviation," Ervin said, USA Today reports.

It is possible, according to USA Today's report, that the only way to truly secure rail and subway cars is to screen every passenger.

"Mass transit systems in the U.S. are vast, a literal black hole," James Carafano, a homeland security expert at The Heritage Foundation, said, according to USA Today. "They would consume every cent we spend on homeland security, and there still would be vast vulnerabilities."