Pedestrian Potential-Collision Standoffs, and Symmetry Breaking

We’ve all experienced this phenomenon: you and someone else are walking towards each other in opposite directions, and you don’t want to collide. Do you shift to the left or to the right? And how should you shift to avoid a standoff? In a new paper on the arXiv, physicists Nickolas Morton and Shaun Hendy of the Department of Physics at University of Auckland have examined this problem through the lens of statistical mechanics. Here is an excerpt from their abstract:

If both make the same choice then passing can be completed with ease, while if they make opposite choices an embarrassing stand- off or collision can occur. Pedestrians who encounter each other frequently can establish “social norms” that bias this decision. In this study we investigate the effect of binary decision-making by pedestrians when passing on the dynamics of pedestrian flows in order to study the emergence of a social norm in crowds with a mixture of individual biases. (…) We construct a phase diagram that shows that a social norm can still emerge provided pedestrians are sufficiently attentive to the choices of others in the crowd. We show that this collective behaviour has the potential to greatly influence the dynamics of pedestrians, including the breaking of symmetry by the formation of lanes.