Transportation between floors in buildings: combining hop-on-anytime with small horizontal footprint

Convenience plays a massive role in our behavior.  Often if there's the tiniest amount of friction, and the effort required rises above a fairly low bar, we won't bother.  Or at least this post is going to assume that's the case.

Here's a way convenience impacts our use of space, which suggests a new mode of specialised transport between floors in buildings.  For the sake of simplicity I'll consider this in the context of shopping.

Lets consider shopping spaces that are distributed over multiple floors.  There are three ways of transporting people between floors: stairs, escalators (I'll lump inclined travelators in with these), and lifts.

These have various trade-offs.  Stairs require the most physical effort, while escalators and lifts require very little.  In normal circumstances, stairs and escalators don't require any waiting to use, whereas a lift will typically require a wait before getting in.  Stairs and lifts can be packed into fairly small horizontal spaces.  For lifts it's basically the horizontal dimensions of the lift itself.  A spiral staircase, or a 'square' staircase (where each flight keeps making a 90 degree turn), can be fairly compact in their horizontal dimensions.  Escalators tend to require a fair amount of horizontal space (they're lengthy).

As far as convenience goes, we can take stairs out of the picture (despite how good they might be for people's health).  That leaves escalators and lifts.  Escalators are very convenient as you can always just hop on them, but they take up a fair bit of horizontal space.  Lifts take up little horizontal space, but you often have to wait to use one. 

In terms of speed, escalators are adequate as long as you only have a few floors to traverse, whereas lifts can be much faster if you have many floors to traverse.

So for a typical multi-floor shopping center, escalators will be your main between-floor transport system.  There's only a handful of floors, so the speed of escalators is adequate, and it's just much more convenient to be able to hop on at any time (plus there's ample room for trolleys).

But what about smaller multi-floor buildings, like you might find on the main street of a smaller town?  Ones that don't have room for escalators (or where it's not worth using the amount of room it would require for an escalator).  (Of course, cost is another factor, but we'll leave that aside for the moment).  They could install a lift, but I think the friction of having to wait for the lift would be too much for the average customer. (And the friction of stairs is going to be too much to have a different set of shops on the second floor).  I suspect this is a contributing factor to why multiple floors often aren't utilised for stores in such situations.  Sometimes you might have the one small store over two floors, but you are less likely to see separate stores on the second or third floor.

What would ideal would be something that has the hop-on-anytime property of escalators but which takes up a smaller amount of horizontal space than they do.

Think of this as setting the requirements for a kind of design challenge.

One design possibility would be where there were vertical shafts running between floors, one carrying platforms up and another carrying platforms down.  The platforms would be like a lightweight form of a lift.  Instead of being an enclosed capsule, they'd just be platforms with railings.  The railings would be designed to fold up, so that so multiple such platforms could be stored in a recessed fashion at each floor, so a person can pretty much always walk up and use one.  They'd be stored there folded up and automatically unfolded for use.

(Another possibility would be a tightly-wound spiral escalator.  As in, a spiral escalator with a small circumference. Spiral escalators exist, but they are quite large, with shallow curvatures.  I suspect a problem with a tightly-wound spiral escalator would be that, even if it could be engineered, it would be a bit disorienting for the rider to be rotating so fast).

Of course, that's just a rough bit of speculation, and the big question is whether a practical system meeting these requirements (of hop-on-anytime and small horizontal footprint) could actually be built.  Another big question is whether it could be cost effective.

What interests me is, if they could, whether it could change the way we use space.  Could it increase the convenience enough such that there would be viable uses of spaces that otherwise would not be viable because of not being sufficiently convenient?  I can imagine applications like making use of multiple floors in smaller retail spaces, that otherwise just wouldn't be convenient enough.  Or perhaps a more convenient way to get between floors in smaller-horizontal-space areas could help people in companies spanning multiple floors communicate and collaborate more effectively.