Escalators. Unlike Elevators (Lifts, for you Brits), Escalators don't/can't have counter weights. But why couldn't Escalators have generators or massive flywheels to generate or store energy of the ones carrying people downward?  That could then be used to help drive the ones carrying people up.,(reply>), Da Hai Zhu escalators do have a counter weight.  A the top of the escalator the stairs go under the escalator and head down this acts as the counter weight.,(reply>), REALLY??,(reply>), Escalators running downwards usually use their motor as a generator an produce electricity when more than two or three people are on them.,(reply>), Well," Tom Scott made a video about another type of elevator: <a href=""https://youtu.be/YgJBD1wf-YQ"">https://youtu.be/YgJBD1wf-YQ</a> so I guess people already experimented a lot with them."