A rather interesting account, going back to Joan Didion and The White Album. An excerpt:
Well, for starters, Caltrans leaned on the municipal engineer of L.A.’s surface streets. They didn’t have jurisdiction over these local roads, so they wanted him to create a “confused and congested situation” (their words) on the surface roads so that drivers would be forced onto the gridlocked freeways. And Caltrans knew that the freeways would be gridlocked, because that’s the way they wanted them.