The proposed bill I've seen people supporting - SB 827, by the SF state senator - defined "along existing transit corridors" so broadly that it covered the entirety of San Francisco and anywhere else with a vaguely functional bus service, and used state preemption of local laws to set a minimum height, remove parking minimums, and require local planners to allow dense mid-rise apartment buildings in the entire area. Its more keen proponents insist that it's absurd to call this radical in any way because it's obvious that dense buildings around transit hubs is the way to go.