Sidewalks are complex environments. Sure, they’re second nature for humans, but the delicate balance of humans on foot, humans on bikes, humans with animals, humans in clusters, and humans on skates, skateboards, or other configurations are a lot for a machine to process. Put that sidewalk on a college campus, where people are walking in all directions, clustering and stopping suddenly, and emerging from buildings, and that’s even more challenging for a robot to navigate. Researchers at Stanford built a machine to learn the rules. And to make it seem extra friendly, they gave it a tie and a straw hat.