Physics of the Running of the People from the Bulls

The running of the people who are running from the bulls at the Running of the Bulls in Pamplona, Spain, begs for some insights. Insights — insights about the running of those people from those bulls — course through the paragraphs of this newly published study:

Pedestrian Dynamics at the Running of the Bulls Evidence an Inaccessible Region in the Fundamental Diagram,” Daniel R. Parisi, Alan G. Sartorio, Joaquín R. Colonnello, Angel Garcimartín, Luis A. Pugnaloni, and Iker Zuriguel, Proceedings of the National Academy of Sciences, vol. 118, no. 50, 2021, e2107827118.

The authors, at Instituto Tecnológico de Buenos Aires (ITBA), Argentina; Universidad de Navarra, Pamplona, Spain; and Universidad Nacional de La Pampa, Argentina, report:

We characterize the dynamics of runners in the famous “Running of the Bulls” Festival by computing the individual and global velocities and densities, as well as the crowd pressure. In contrast with all previously studied pedestrian systems, we unveil a unique regime in which speed increases with density that can be understood in terms of a time-dependent desired velocity of the runners. Also, we discover the existence of an inaccessible region in the speed–density state diagram that is explained by falls of runners. With all these ingredients, we propose a generalization of the pedestrian fundamental diagram for a scenario in which people with different desired speeds coexist.