every year Thousands of people gather in the city of Pamplona, in northeastern Spain, for a chance to flee for their lives as six fighting bulls are launched to launch an assault through the city. There are dozens of injuries each year, and there are at least 15 recorded deaths since 1910. But the event matters more than just adrenaline junkies and animal rights activists. Paper just published in Proceedings of the National Academy of Sciences He describes the insight the event provides into the psyche of panicked crowds.
Enjoy more audio and podcasts iOS or Male appearance.
This is a useful topic to explore. Architects, civil engineers, and urban planners must try to work out how people should act in the event of a disaster such as a fire, flood, or terrorist attack so that they can design their creativity to avoid potentially fatal crushes. Unfortunately, solid information is hard to come by. After all, ethics review boards are likely to decry researchers who put volunteers at mortal danger just to study how they might behave. But Daniel Baresi, a physicist and computer scientist at the Polytechnic Institute of Buenos Aires, and lead author of the research paper, realized that the Pamplona bullfighting offers the perfect natural experience.
Dr. Parisi and his team went to two different rooftop locations in Pamplona in July 2019, and recorded footage of the runners releasing the animals. A wave of people running at full speed raced past their cameras a few seconds before the bulls. The researchers returned their recordings to the lab to calculate the runners’ speeds, crowd density and the probability of a runner’s tripping and falling. They also examined the tracks of the bulls, the responses of individual runners when the bulls approached them, and the relationship between runner group density and speed.
Perhaps not surprisingly, the researchers found that the runners increased their speed as the bulls approached. Less expectation was the finding that the speed of individual runners increased with the density of the crowd. At a maximum crowd speed of about four meters per second, the density reached approximately one pedestrian per square metre. This finding goes against the assumption in architecture and urban design circles that people will slow their pace as group density increases, in order to reduce the risk of collision, which could lead to falls and possibly, injury or death of a runner by others. Dr. Parisi’s data suggests that crowded groups of fast runners are already at risk: Of the 20 people who have fallen, all have done so within a dense, fast-moving group. Most (14 out of 20) were involved in two or more people, with one other stumbling.
However, it seems that in the midst of this moment, people do not care much about the danger of crashing into each other, nor do they slow down. So the onus is on urban designers to come up with how best to plan the construction of alleys, tunnels, future bridges, and other passages that restrict flow. The only option might be to make it wider.
To enjoy more of our mind-expanding science coverage, sign up for Simply Science, our weekly newsletter.
This article appeared in the Science and Technology section of the print edition under the heading “Architects and the Bulls Competition”