> Try the same thing on Mission, Howard, Folsom, Harrison, Geary, Van Ness, etc. and you’ll see a very different story.

Probably not. More car lanes = more cars. Less car lanes = less cars. People switch modes, drive elsewhere, don't take trips, etc. Time and time again (Paris, London, NYC, SF, Portland, Seattle, and many many more) cities have taken space from cars without carmageddon.