The space on an escalator is quantized. You don't stand on the same step as the next passenger, lest you be accused of frottage; the closest packing in the direction of travel is one person per step. The inter-step distance on escalators is large enough to acommodate walking motion.
>The inter-step distance on escalators is large enough to acommodate walking motion...one person per step
In theory possibly but I've never seen that. It's rare for standing passengers to be one per step. In the real world it's probably 3 per 4 steps standing, 1 per 4 steps walking. I think what we need are coordinated escalator classes taught in a similar manner to ballet, for greater utilisation.
1 per 4 steps indicates that it's not a busy time. Or it's one of those long escalators that don't have too many takers for walking. Once the walkers get through the crowd and get on the escalator, they suddenly have lots of space, if a large proportion chooses to stand. It's not because they need space; they aren't standing at the bottom waiting for a space of three extra stairs to open before they start to walk; it's just that by the time they get on, the previous walker is already that far ahead.
The standers are creating the rate-limiting bottleneck, basically. I suspect that even if the mix is 50:50 walkers:standers, the walkers will spread apart more. You probably need something like 60:40 or 70:30 to fill the walking side to better capacity. Or some priority line for walkers, long before the escalator, so that walkers can aggregate together from the get-go. Let all the walkers rush by, and then the remaining standers can use both sides.
Example:
Suppose 300 people get off the same train, and face a long escalator. Nobody wants to walk, except for five people. Also, everyone respects the "stand on one side" rule.
Now suppose those five people are mixed randomly into the crowd. They have to wait for all these walkers to board the escalator and end up spaced far apart from each other. Perhaps by the time the second walker gets on the escalator, the first one is already at the top.
Now suppose that the walkers are given priority access, through a separate queue. (Which they should: I mean everyone is already reserving half the escalator for these guys, yet not letting them get to it, right?) So now, these five people can just march straight to the escalator as a group, get on it, and march on up, remaining closely packed. After that, no more walkers are left in the fast queue. Moreover, everyone else can see that. So, then remaining people start using the full escalator.
Problem (mostly) solved, all-round.
This is almost the behavior I seen in Japanese train stations. There isn't a formal separation of queues, but just about. People separate themselves into walkers or standers based on their intent and start to line up accordingly before reaching the escalator.
