the stations where they encouraged people to stand on both sides were so far underground that almost no one chose to walk up. In the case of the Bay Area the “walking” side is often fully utilized and it wouldn’t make sense to stand on both sides.
BART now discourages "stand right, walk left" because it leads to "'uneven wear' on the escalator's gears, which can lead to more breakdowns and need for repair."
Maintenance problems aside, I'm usually surprised at how consistently people follow the stand-right "rule." Typically, everyone ahead of me followed it in my experience with BART.
Standing is denser than walking, so the throughput is greater (at the cost of latency, for those who would walk). I believe the station only encouraged the break in tradition at peak times, when there are significant numbers of people waiting to get on.
> Standing is denser than walking, so the throughput is greater
Doesn't this depend on the walking/standing density ratio and walking speed/escalator speed ratio?
Let say the walking density is 1/2 of the standing density. If the walkers walk at the speed of the escalator (i.e. their speed relative to the ground is 2x the speed of the escalator), then the throughput is the same.
Holborn's escalators are over 23 metres tall, as tall as a six or seven storey building. Very few people will walk up the entire escalator, essentially limiting utilisation to 50%.
There are other issues than eagerness to walk, like physical disabilities and collision avoidance. Ultimately two-speed traffic only works better if you're far from congestion, I believe.
Maybe it's cultural or depends on how eager to walk people are as to utilization factors.