The fastest crowd may have to stand still
When an escalator is crowded, the quickest way to move the whole group is often for people to stand on both sides rather than leave one side open for walkers. It feels counterintuitive: walking seems faster for each person. But an escalator carries people in a steady stream, and its capacity depends on how many can ride at once.
Leave half the steps empty and the machine keeps moving those gaps upward. Fill both sides with standing passengers, and more people travel on each step, so the escalator can carry a denser flow.
Why the walking lane can slow everyone down
Walkers move at different speeds, need room to pass, and may bunch up when someone ahead slows or stops. That makes the open lane less consistently usable than it looks. Meanwhile, people standing single-file on the other side occupy far fewer steps than a packed two-abreast line would.
The tradeoff is between individual speed and crowd throughput: a walker may reach the top sooner, while the crowd as a whole moves less efficiently. On a busy escalator, standing side by side can therefore get more people upstairs in the same stretch of time—even if it asks the most impatient passengers to resist walking.
