Unlike normal cities’ flat-fee subways, D.C.’s Metro charges different fares based on how long the trip is, which require tourists to determine their start and end points as well as whether they are traveling at regular or peak hours. Get that calculation wrong, and you’ll be trapped underground by an unsympathetic exit gate and forced to panhandle until you’ve gathered enough change to pay the difference. Despite this system, some tourists managed to escape Metro, so WMATA enacted a new fare structure in July that added a secret $1 charge to paper cards. Now, even if a tourist scrutinizes the fare tables and successfully determines that a rush-hour trip from Dupont Circle to Union Station should cost $2.10, they’ll still be a dollar short unless they had the foresight to invest in a $5 SmarTrip card—or noticed one of the taped-up signs now posted around the system announcing the extra fee. Never let it be said that Washington can’t close loopholes.