Preliminary Plan: Minatoma Project (1948)
This is one of a pair of plans for the Minnatoma Project (as the text of the plan spells it), an elevated viaduct that would have run between Minna and Natoma Streets from the Transbay Terminal to Van Ness and then to Market.
In this version, it would have been a three-level structure, with car parking at ground level and on the first level, a six-lane freeway on the second level, and a six-lane busway on the top level. The western end terminating at Market and Waller makes more sense if this was to be constructed as part of the Waller Street widening and tunnel project that was proposed in 1945. Several new midblock pedestrian routes with moving sidewalks would have been provided between the stations and Market Street.
Scott Dowdee at the Department of City Planning has a great rendering of this project and I thank him for letting me post a copy of it.