(vargklo/flickr)

The escalators on the D.C. Metro are very tall and they are always breaking. This sucks a little if you are just lazy like me, it sucks a lot if you’re on crutches or you have a suitcase. But even when you know the escalator is broken, and expect it not to be moving, for many people, there’s still a moment of disorientation when you step on and start climbing, a weird imbalance that doesn’t happen with equally motionless stairs. But a broken escalator is stairs. Hence the mystery.

Luckily, chances are that if you’ve stopped to wonder about something before, somewhere, a researcher has likely done the same. In this case it was R.F. Reynolds and A.M. Bronstein, who in 2003 published a study called “The Broken Escalator Phenomenon,” which they defined as “an odd sensation of imbalance, despite full awareness that the escalator is not going to move.”

To recreate the feeling in an experimental setting, the researchers used a mobile sled, which participants stepped onto from a stationary platform. First they stepped onto the sled 10 times while it wasn’t moving, then stepped onto it 20 times while it was in motion. Then the researchers stopped the sled, clearly told the participants it wouldn’t be moving, and had them walk onto it again. Even though they knew the sled wasn’t moving, they still walked onto it too fast, swaying their torsos forward. “There was a forward sway of the trunk by about 14.9 centimeters above that of the final resting stance position,” the study reads. Many of the subjects said they were surprised by the feeling, and some of them compared it to walking onto a broken escalator.