The city started the traffic system in preparation for the 1984 Olympics at a handful of intersections surrounding the Los Angeles Memorial Coliseum, where crowds flocked to watch Carl Lewis and Evelyn Ashford.
Other cities have chased to keep up, adopting centralized control of at least some traffic signals. But Los Angeles has remained at the forefront, with a system that is not only more widespread, but also faster and more autonomous than most others.
Now, the magnetic sensors in the road at every intersection send real-time updates about the traffic flow through fiber-optic cables to a bunker beneath downtown Los Angeles, where Edward Yu runs the network. The computer system, which runs software the city itself developed, analyzes the data and automatically makes second-by-second adjustments, adapting to changing conditions and using a trove of past data to predict where traffic could snarl, all without human involvement.