I was at a large baseball stadium today and they had escalators to bring everyone up to the upper levels at the beginning of the game. At the end of the game, when everyone was leaving, the escalators were shut off and blocked off and everyone was walking down ramps to exit. I was thinking it should be possible to have everyone take the escalators down and the motors could be used as generators to generate electricity to sell back to the electric company. Does anyone do this? Is there a practical reason why this wouldn't work?