Protecting so-called soft targets like railway stations has been a challenge for security officials, who are tasked with ensuring safety but need to balance that with ensuring the smooth movement of hundreds of thousands of travelers.
The TSA's administrator, David Pekoske, said in November that airport-like security, in which passengers have to line up for personal and carry-on bag screening, was not necessary at rail stations.
"We don't intend to roll out anything like what we have in the airports," Pekoske said, adding that random passenger checks and police with canines among other measures are sufficient. "We are satisfied at his point."
However, in December, a man was injured by a pipe bomb he had attached to his torso with Velcro in a blast that went off at a 42nd Street subway station in Manhattan.
The technology aims to help officials detect concealed suicide vests or other improvised explosives, the TSA said, which is better known for its passenger screening at U.S. airports.
"The use of these devices enables a rail or transit agency to help safeguard against terrorist threats in the mass transit environment," the TSA said. "TSA is supplying two models of the equipment for the purposes of the pilot."
The TSA last year started testing the equipment in the Los Angeles transit system.