Friday, 23 October 2015

How do crowds cross at traffic lights?

You see it all the time in big cities where there are lots of people using the footpaths. Dozens of people will gather at the crossing point beneath the traffic light waiting for the signal to turn green, and when it does they cross the road, threading together with the crowd coming across the road the other way seamlessly.

It's sort of magical how this process happens hundreds of thousands of times each day in cities across the world. Each person in both crowds knows there is only so much time available to cross the road and they do so without fuss, without connection, without practically even brushing a sleeve against the shoulder strap of someone coming the other way. Just by making tiny adjustments in their trajectory, each person in both crowds manages to find the optimal route through the oncoming crowd to the other side before the cars start moving again.

This is something extraordinary and it's practically unconscious. We just somehow seem to find the shortest way to the other side through the oncoming crowd without talking to anyone, without making any outward signal, and without hurrying. I can't see how self-driving cars are going to become a reality until the boffins can develop the kind of hive mind that allows crowds crossing at traffic lights to thread together soundlessly and in complete harmony, to reach the other side of the road. Once they come up with something as seamless and effortless as this, I'll start to take them seriously.

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