Because Metro wants you to stay stationary. “From our perspective, the safest way to use the escalator is to stand on the right and hold the handrail,” says spokesman Dan Stessel. “We don’t encourage people to walk.” Metro does run announcements encouraging customers to stand to the right—but without adding that they should walk on the left. “It’s a subtle distinction,” Stessel admits. Even if the system were to abandon its anti-walking stance, this kind of signage would violate engineering codes: The American Society of Mechanical Engineers only permits certain types of signs within 10 feet of an escalator; “stand to the right” isn’t on the list. So what should you do if you find yourself stuck behind a pack of tourists and running late to work? Just ask them to move. “A simple ‘excuse me’ is usually all it takes to educate an out-of-tower to our ways,” Stessel says. “This approach is a lot more effective than any sign, and it’s free.”