The Metro system of buses and rail in Washington, DC, started implementing random bag checks last year. Right now, the checks appear to be limited to bags and only for detection of explosives. Of course, if you're heading towards a station or stop and see a table set up to do the checks, it's not that hard to turn around and walk to the next one. Or, you could hope that your not selected for the check. But what happens if you refuse? You immediately become a suspect (but you must already be suspect if you undergo a search, right?) and will be surveiled.
If you think this fight is only about cancer-causing radiation, or only about the luxury of air travel, or only about preventing the next 9/11, you are mistaken. This is about our rights as individuals being stripped from us.
H/T Bruce Majors