Senate Homeland Security and Governmental Affairs Chairman Joe Lieberman (ID-Conn.) called for expanded security measures on the nation’s railways and buses following terrorist attacks in Moscow’s subway system.

“The threat is real to non-aviation transportation,” Lieberman said on NBC’s “Meet the Press.”

In addition to the Moscow bombings, Lieberman cited terrorist attacks on trains in London and Madrid, and said new efforts are underway in the United States to protect ground-based mass transit in ways both visible and not obvious to passengers.

“All you’ve got to do is look around the world,” Lieberman said. “These are targets.”

“Non-aviation is the vulnerable part of our transportation system, and we frankly need to give it more than we’re giving now to protect the American people. I worry about this,” he added.

Appearing on the same program, Rep. Jane Harman (D-Calif.) also praised new security measures in airports aimed at detecting suspicious behavior patterns.

Harman, the chairwoman of the Homeland Security Subcommittee on Intelligence, Information Sharing and Terrorism Risk Assessment, said the new systems would spot threats from people who are not the “stereotypical Muslim male” between the ages of 20 and 40.

“Terrorists come in all shapes and sizes,” Harman said.