WASHINGTON – If you’ve ever swiped into the Metro and felt a stranger suddenly on your heels, congratulations-you’ve been “piggybacked.” This term refers to the fare-dodging move where someone closely follows a paying customer through the gates, taking advantage of their swipe to slip in or out without paying. The tactic, equal parts awkward and aggressive, has gained renewed attention as the Metro steps up its fight against fare evasion with five-foot-tall gates.