Sky Lobby

A sky lobby is an intermediate interchange floor where people can change from an express elevator that stops only at the sky lobby to a local elevator which stops at every floor within a segment of the building. When designing very tall (supertall) buildings supplying enough elevators is a problem – travellers wanting to reach a specific higher floor may conceivably have to stop at a very large number of other floors on the way up to let other passengers off and on. This increases travel time, and indirectly requires many more elevator shafts to still allow acceptable travel times – thus reducing effective floor space on each floor for all levels. (The other main technique to increase usage without adding more elevator shafts is double-deck elevators.)

The sky lobby was invented by Fazlur Khan, a Bangladeshi American structural engineer, to resolve this issue. It was first used in the John Hancock Center in Chicago.