One of the most interesting things about cities is that as they grow their "urban metabolism" also tends to increase. People become more productive. Economic output increases. It becomes easier to hail a cab (which is a test I like to use). And, according to this recent article by CityLab, people walk faster.

Yes, research has shown that there's a correlation between population size and the speed in which people walk. And some of the studies go as far back as the 1970s — like this one from psychologists Marc and Helen Bernstein:

In many ways, this makes intuitive sense. Life in the big city is a fast paced one. But why exactly do people start literally walking faster? The most probable answer seems to be, quite simply, that time is money. Subsequent research from the 1980s and 1990s has revealed that the best predictor of fast walking is economic output.

When a city grows larger, they wrote, wage rate and cost of living increase, and with that the value of a resident's time. As a result, "economizing on time becomes more urgent and life becomes more hurried and harried," Walmsley and Lewis suggest. (Source: CityLab)

The first thing that crossed my mind when reading all of this is that there must be some sort of upper limit. Humans don't just keep walking faster and faster as the city in which they live in grows bigger. If that were the case, the mega cities of the world — such as Tokyo — would have people sprinting around all the time. But that's obviously not the case.

So this is a topic that could probably use some more data. And I would imagine it would be a lot easier to collect today given that we all now walk around with mobile sensors in our pockets (our smartphones). And pretty soon we may have mobile sensors on our wrists (smart watches).

I would certainly like to see more data on this. The idea of an "urban metabolism" has always interested me.

Image: Dundas Square, Toronto via Flickr