Pedestrian crossings generally showcase the best in pedestrian behavior, with people naturally forming orderly lanes as they cross the road, smoothly passing those coming from the opposite direction without any bumps or scrapes. Sometimes, however, the flow gets chaotic, with individuals weaving through the crowd on their own haphazard paths to the other side.

Now, an international team of mathematicians, co-led by Professor Tim Rogers at the University of Bath in the UK and Dr. Karol Bacik at MIT in the US has made an important breakthrough in their understanding of what causes human flows to disintegrate into tangles. This discovery has the potential to help planners design road crossings and other pedestrian spaces that minimize chaos and enhance safety and efficiency.

In a paper appearing in the journal Proceedings of the National Academy of Sciences, the team pinned down the precise point at which crowds of pedestrians crossing a road collapse from order to disorder.