Illustration of the lane formation phenomenon in a crowded walkway in Bordeaux, France (photo by Simon Garnier)

When it has been first observed in the 1970th and first reproduced by computer simulations in 1995, lane formation has been quickly labeled as a smart collective behavior, a nice illustration of the wisdom of crowds. In fact, this collective pattern is an efficient way of organizing counter flows to minimize avoidance maneuvers and frictions among people moving in opposite direction, just like cars in highways. The major difference with cars, however, is that highways of pedestrians are self-organized: They don’t require any specific centralized traffic rule. They appear naturally, when it’s necessary… That’s the magic of self-organization!

Snapshot of the experiment

So, to answer that question, we have designed a big lab experiment to characterize the features of lane formation. For this, we hired up to 60 participants and put them in a large ring-shaped corridor. Half of them were instructed to walk clockwise, and the other half to move anti-clockwise. Participants were randomly located in the corridor at the beginning. At the starting signal, they started to move in their walking direction. As expected, it took about 20 to 30 seconds before the two opposite flows segregate almost perfectly, without giving the participants any specific instructions about that. A very nice emergence of order out of disorder, as it has been theoretically described in the study of self-organized systems. The video below shows an example of what we observed during  the experiment, after the tracking of pedestrians.

This figure shows that the global traffic efficiency decreases as the speed difference among pedestrians increases. The three colors correspond to different crowd size in the corridor, from 30 to 60 individuals.