Traffic

I've always been fascinated by traffic. (I grew up in LA, so I had plenty of time to indulge my interest.) City streets are a complex system in which seemingly insignificant changes - a broken street light, a stalled car, a poorly designed highway merge - can have dramatic consequences. In this sense, it's a useful metaphor for all sorts of intricate systems, from gene regulation to neural networks.

Perhaps the single greatest mystery of my childhood was this: Why do freeways get clogged when t