A note to tourists in Washington, DC: please walk faster. This is not Disneyland; your tour groups are blocking the capital’s vital sidewalks with your 0.35 mph human obstacles. As much as possible, try to match pace with native Washingtonians, who walk at about 5mph below the posted freeway speed limit. Faster if it’s a cold day.

(Visiting New Yorkers, on the other hand, may want to consider slowing down, so as to avoid the relativistic space-time distortion that occurs at near-light speeds.)