Slidewalk
A moving sidewalk; a conveyor belt for people.

This term refers to a way of moving large numbers of people over a relatively short distance (over flat surface).

He had stepped on to the corridor slidewalk and had coasted halfway to the elevator before he realized that Phy had followed him and was plucking timidly at his sleeve.
From Sanity, by Fritz Leiber.
Published by Astounding S-F in 1941

The slidewalk is also a Heinlein favorite; you'll find references in his 1947 story It's Great to be Back!, his 1948 story Gentlemen, Be Seated and his 1948 novel Space Cadet:

They went on up to the subsurface level and took the crosstown slidewalk out to the rocket port. The slidewalk tunnel broke the surface at one point, becoming a pressurized shed; a view window on the west looked out on the surface of the Moon—and, beyond the hills, the Earth.
It's Great to be Back!

It was a dull trip-climb on a scooter, ride down a completely featureless tunnel, climb off and go through an airlock, get on another scooter and do it all over again. Mr. Knowles filled in with sales talk. "This is temporary," he explained. "When we get the second tunnel dug, we'll cross-connect, take out the airlocks, put a northbound slidewalk in this one, a southbound slidewalk in the other one, and you'll make the trip in less than three minutes. Just like Luna City-or Manhattan."
Gentlemen, Be Seated

Don left the booth and looked around for a cab stand. The station seemed more jammed than ever, with uniforms much in evidence, not only those of pilots and other ship personnel but military uniforms of many corps-and always the ubiquitous security police. Don fought his way through the crowd, down a ramp, along a slidewalk tunnel, and finally found what he wanted. There was a queue waiting for cabs; he joined it. Space Cadet

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