This morning I took the mid-level escalators down to Hong Kong station so that I could catch the express train to the airport. At over 800m, it is supposedly the longest outdoor covered escalator system in the world.

If you’ve ever walked the streets of Hong Kong you’ll know that the ground plane can be inhospitable at times. There’s limited space, but no shortage of steep pitches. I can’t imagine having a physical disability and trying to navigate this city.

So this system must have been a real innovation when it was constructed in the early 90′s. In total it moves up and down about 135m in elevation. That’s about the equivalent of a 45 storey tower. And I got down from the mid-levels and was on a train to the airport within 15 minutes.

But because the streets here are so narrow it’s a unidirectional system with one line of escalators. They bring people down to the CBD during the morning rush, but then the direction flips and they bring people up the hill for the remainder of the day — until midnight I believe. Living near these escalators is considered a win.

Hong Kong Island surely isn’t the easiest of environments in which to build and operate one of the world’s most important global cities. There’s relatively little developable flatland. But they more than made it work by being creative and by building up. Hong Kong is not just a tall city, but a truly vertical city.

Too bad my efficient morning commute was followed by a cancelled United flight. Tomorrow is not going to be a fun day travel.

I am one of those people that gets annoyed when people don’t follow proper escalator etiquette. The etiquette being: stand on the right; walk on the left. Some cities – London and Tokyo come to mind – are draconian about this.

But it turns out that this is not always the best way to optimize throughput. A recent study conducted in London found that during peak periods – such as the morning rush hour – it is actually better for everyone to stand still.

What they found was that when 40-60% of people chose to walk up on the left, maximum throughput was 115 passengers per minute. But when everyone stood still maximum throughput increased to 151 passengers per minute.

The reason for this is that walking takes up more space than staying put on one step. When demand is low, this has no impact on capacity. But as soon as people start slowing down to avoid the set of legs in front of them, a bottleneck occurs and capacity starts to drop. 

This is not dissimilar to what happens in traffic jams. Imagine if during peak periods all of the cars could separate themselves by only a few inches and travel at exactly the same (slow) speed. That’s not going to happen until self-driving cars hit the road, but it would be more efficient than the current chaos of distracted drivers starting and stopping.

All of this being said, since this finding only applies during very busy times, I plan to continue being annoyed when proper escalator etiquette is not followed.