We've spoken before about Saudi Arabia's "The Line" project. At first, I wasn't sure if it was real, but it is, and it's now under construction. We then spoke about whether a 170-kilometer line is an optimal urban form for a city, and the answer, according to this study, is that it's not. The problem with a line is that it actually maximizes the average distance between inhabitants. This makes sense because you could have two people living and working 170 kilometers apart.
On the other hand, if you maintain the same built-up area and take the opposite kind of geometry -- a circle -- you actually minimize the average distance between inhabitants. It's for this reason that older cities (the ones that weren't masterplanned) have tended to grow radially and not linearly (unless there were geographic features forcing it to grow in a certain way). So there is a strong argument to be made that The Line is a suboptimal plan for a new city.
But here's what's interesting: many cities already follow a somewhat similar approach. They don't do it as absolutely as The Line, but they do it in the way that they zone for higher densities and a mix of uses only on their main corridors. Example:
Concentrating density on just one street creates less livable neighborhoods.
Medium density projects should be spread over a bigger area.
So I guess I was wrong. I thought "The Line" in Saudia Arabia was never going to be built -- at least not in its current incarnation. But apparently it is now under construction, and it is still planned to be 170 km long and house some 9 million people when it's complete. I suppose something could happen between now and when all 170 km are complete, but I'm happy to accept that, for the time being, I was wrong.
Now it's time to ask ourselves what a 170 km long city would even be like. To answer that, here is a fascinating article from npc Urban Sustainability describing how mobility and urban interactions are likely to work in this kind of a linear city. And it turns out that a line is actually an optimal urban form if you're trying to both maximize commute times and maximize the average distance between inhabitants:
One of the most critical aspects related to The Line is distance. If its 9 million inhabitants are homogeneously distributed in the city, each km will have roughly 53,000 people. If we randomly pick two people from the city, they will be, on average, 57 km apart. Although The Line occupies only 2% of the surface of Johannesburg, if we pick two random people in Johannesburg, they are only 33 km apart.
As a gross generalization, there are probably two ways in which one can approach the building of a new building. The first is based on demand. You believe that there is demand for new housing or new office space or some other use, and so you decide to build new space in order to satisfy that exact demand.
Sometimes developers get it wrong and build too much space or the wrong kind of space, but the reason for building remains the same: you believe that there is a market waiting for you.
The second way to build is to completely disregard the market and just build whatever you feel like building because it is going to serve some other alleged purpose. And that is arguably what is happening in Saudi Arabia with The Line and what happened in places like North Korea with its "Hotel of Doom."
I suppose that there is a chance that somebody in North Korea believed (or pretended to believe) that there was demand for a skyscraper that was 1,000 feet tall and housed 3,000 hotel rooms, but in reality, the real reason was that leadership thought it looked cool and that it would make for good propaganda.
To be fair, there was probably also some hope that it would spur demand and attract foreign investment. But it's still a case of just building whatever you want.