If you’re walking to the grocery store, you’re probably trying to take the shortest route. But does that work? Research from MIT shows that although people are very good at navigating cities, they rarely take the shortest route. The MIT researchers argue that this is because it requires less brain power than determining the shortest route.
The shortest distance between two points is a straight line, but in a city, streets and bridges determine your route. To find out how people choose their route, the researchers analyzed GPS data from more than 550,000 everyday walking routes of more than 14,000 anonymous pedestrians in the American cities of Boston and San Francisco. Their findings appeared Monday in Nature Computational Science.
Back by another route
The researchers compared these with the routes that according to Google Maps are the shortest. This shows that people deviate more from the shortest route the greater the distance. In addition, they saw that people who walked back and forth between two points – for example to the supermarket and back – regularly took a different route back than there.
According to the researchers, people often choose paths that point as much in the direction of their destination as possible, even if that means longer travel times. Then people at an intersection are more likely to choose the road that points most in the direction of their destination, even if it is shorter to first walk in an apparently wrong direction and then reach the destination via a right angle.
Bats and cats
Such so-called vector navigation has also been seen in animals, such as bats and cats. It seems to be the most practical method if you don’t have a complete map with distance measurements at your disposal, like a navigation system. Vector navigation may take less energy than pondering the very shortest route. And that outweighs a short detour, the researchers say.
“I think it’s good that more research is being done into the movement patterns of pedestrians in the city,” says Lara Zomer, who obtained her PhD at TU Delft earlier this year on bicycle trips. “That is important to enrich the traffic and transport models that we have been using since the 1970s. Those models, which we use to better organize cities and predict crowds, for example, were rather based on the idea that people optimize everything, regardless of whether they walk, cycle or drive. By understanding the difference between the behavior that people show and what is optimal according to an algorithm, we can make those models more realistic.”
Zomer does note that the MIT researchers lump all pedestrians together, while there is a great deal of difference between the ways in which people determine their route. In addition, not everyone will know as accurately as the algorithm how great the distance is and at how many degrees their destination is. The researchers themselves also state that they lacked information about the pedestrians and their destinations. For example, it may be that someone deliberately detours to a sandwich shop, because the longer route is more beautiful or more sheltered. Such information is more difficult to obtain, but can make the models even better and more humane.
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