4 ideas
Banham divides Los Angeles into four ecologies. Surfurbia is the beach strip. The Foothills are the hillside enclaves of the rich. The Plains of Id are the endless flat grid of ordinary suburbs. Autopia is the freeway system that ties the other three together. Each ecology is defined by its terrain, how you move through it, and how people live in it rather than by administrative boundaries, and each produces its own kind of architecture.
The buildings that best express a city are often not its designed monuments. They are its roads, beach houses, hamburger stands and custom dwellings, which respond directly to how people actually live there. Reading a place through these ordinary artefacts reveals an order that a canon of landmark buildings hides.
Los Angeles lacks a dominant downtown, but it is not chaotic sprawl. Its coherence comes from a continuous movement system, the freeways inherited from an earlier streetcar grid, which makes every point roughly equally accessible. A city can be organised by the ease of moving between points rather than by distance from a single centre.
He treated the freeway as a single comprehensible place, a coherent state of mind in which Angelenos spend much of their lives. He reported that driving an interchange like the Santa Monica/San Diego intersection was a kinetic architectural experience comparable to seeing a great building.