If something gets in the way of the door--a person's foot or a roof panel that's hanging down--the electric motor that closes the train door has to work harder and produces more current.

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There is an old adage that when one door closes, another opens.

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To create the mechanics behind the wall, which opens and closes like a garage door, Mr. Peterson worked with McLaren Engineering Group, an engineering team that has done sets for Cirque du Soleil.

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