Commuter Crunch

During his rush-hour travels on Washington’s Metro, Michael Fu noticed two kinds of people using the escalator: those patiently waiting to board the clogged right side, and the more energetic commuters bounding up the open left lane.

The Smith Chair of Management Science knew the unwritten rule of escalator etiquette—stand on the right, walk on the left—but still, the long line seemed like both a potential safety hazard and inefficient.

Fu, who studies decision-making under uncertainty, set out to determine the optimal times to walk or stand on an escalator. He used mathematical models, adjusting for factors like platform capacity and escalator length, and relied on queueing theory and pooling methods.

His research, published in the journal Systems, found that during high-congestion periods, standers should abandon underground protocol and stride confidently into the left lane for the good of the order. Only later should they slide right to keep the left lane moving.

The approach won’t always get the most hurried travelers out of the station as fast as possible, Fu acknowledges. But adding a minute or two to a commute is a fair tradeoff for eliminating bottlenecks, he reasons.

“If your objective is to clear the platform, then everyone should get on the escalator as quickly as possible,” he says—even if it makes you a temporary left-lane hog.