How many streets are there?

“Great, wide, beautiful, wonderful World,
With the wonderful water round you curled,
And the wonderful grass upon your breast,
World, you are beautifully dressed.”
Part of a not a very good poem by William Brighty Rands

A couple days back I said “it’s a small world” because that was the response that was clearly expected of me at that point in the conversation, and if I said something else, it would just be annoying.

I didn’t mean it, however, because in fact the world isn’t small. It’s very large.

The world being large is one of the greatest things about it – you’re never going to run out of new things to see, new places. new experiences, if you want them and can access them,  for as long as you live. Thinking about how giant the world is, for me, one of the easiest ways to feel optimistic. And thinking that the world is small usually leads to the mistake of thinking that all people are basically like you and your group of friends in every way. So I actually greatly dislike the “it’s a small world” idea.

That's one street for Ubley, now just to count every other town everywhere in the world...

That’s one street for Ubley, now just to count every other town everywhere in the world…

I was thinking about all of this right after saying that it was a small world, and began to get sidetracked in thinking about exactly how big the world actually was. Pretty soon, I asked myself how many streets there were in the world. Since I was at work, I didn’t have a pencil or paper or access to any information whatsoever. I decided the simplest estimate would be to scale up Vancouver. It’s less street-dense than most cities, but more street-dense than many places where people live. I guessed Vancouver proper had roughly 200 streets and a population of 800,000. At 1 street / 4,000 people, we get roughly 2 million streets.

On one hand, this number seems too big: what of all the people who live where there are no streets at all? And what about where the streets have no name? Do we still count those? On the other, it seems way too small. I think I can easily name about 2000 streets (1st ave, 2nd ave,… OK, fine. I’m not going to try it). But the idea that I know .1% of all the streets in the world seems crazy. So I wanted to ask, what’s a way to make a better estimate? First, a better city than Vancouver may be found. In any case this method will help us bound our estimate: somewhere between 700,000 streets (using estimated Manhattan) and 7 million (using a Vancouver suburb).

Rather than using (streets/people)x(people), it may be more appropriate to pick an area, look at the number of streets, and then scale up. For instance, what if we determine the average population density of land (7 billion /(30%*4*pi*(6400 km)^2), or approximately 45 people/km^2) and then look at some area which matches that average density, see what its street density is, and then scale that up to all land? Let’s imagine a village of 180 people spread over 4 sq. km. Picture that in your mind, and I would say that it has about 5 streets. Now multiply that by the number of 4 sq. km areas in the world, and you get almost 200 million. The problem with this way of doing it is that the number of streets as a function of number of people is very much sublinear, especially once you get to having at least a few streets in an area. That is, the number of people needed to make each additional street keeps growing. So the above is going to be a wild overestimate of the number of streets in total, which is what we do see. We can get a better result by starting with a much bigger sample area. Say some square cut out of BC. At 45 people/sq km, the roughly 3 million people of the lower mainland fit in a roughly 250 km x 250 km sized square. My guess is this corresponds to roughly the US border to beyond Pemberton in one direction, and from the Strait of Georgia to beyond Hope (beyond Hope!) in another. How many streets are in this section? My guess is somewhere around 1,500. Scaling that up, we get somewhere in the neighbourhood of 3.6 million streets in the world.

The problem still remains that I don’t know, and don’t have a good way of guessing at, the question of how streets are arranged outside the developed world. For example, if you ask me how many streets there are in the Democratic Republic of the Congo, I couldn’t offer you any reasonable guess.

Another possibility, and one that somewhat reduces the “first world blinders” problem, is to use something like the earth location sampler used in this xkcd what-if, and look at street densities of various locations (as long as your “sample area” is large enough). The problem here is that finding a location with any streets at all is going to be quite rare, so you will need lots of sampling to get a reasonable answer.

The question is very ambiguous (what counts as a street?) to the point where I think even if you somehow could (and decided to) count all the streets by hand, you could get answers off from each other by a factor of 2 or 3. And yet, the crazy thing is, I bet if you asked google maps to just count them all, for example, you’d get a very specific answer.

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One Response to How many streets are there?

  1. Nico says:

    This was a nice procrastination break at my government job 🙂

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