From Forbes magazine:
Documents Reveal TSA Research Proposal To Body-Scan Pedestrians, Train Passengers
Giving Transportation Security Administration agents a peek under your clothes may soon be a practice that goes well beyond airport checkpoints. Newly uncovered documents show that as early as 2006, the Department of Homeland Security has been planning pilot programs to deploy mobile scanning units that can be set up at public events and in train stations, along with mobile x-ray vans capable of scanning pedestrians on city streets.
You can read the whole article here.