This is part of the Public Health (Control of Disease) Act 1984, sections 33 and 34: Public Conveyances.
An interesting discussion regarding this law (and a few others) can be found here.
According to Chapter 6 of the San Francisco Housing Code, “Private and public storage garages in apartment houses and hotels shall be used only for storage of automobiles.” Failing to comply with the law can lead to fines of up to $500. [Added by Ord. 399-89, App. 11/6/89; amended by Ord. 161-92, App. 6/4/92; Ord….