Mobile Elevators

Perhaps a workable element of a sci-fi story, but something that would be pretty cool in real life, too.

Elevators that go up and down through buildings, as usual, but that also settle into trams that travel horizontally from building to building.

Basically, a combination elevator and subway — though the trams could be at any level of the buildings.

When trams pick up an elevator — whether single-person pod or multi-person — it leaves behind an empty elevator pod, so users in the building always have the elevator transport they need.