Interesting. At 1.10 cars per household, and 2.26 people per household, about 47% of SF residents own cars. (Though subtracting out the under-18 population means 55% of driving-age residents own a car.) Also, given there must be some people who own more than one, the actual percentage is probably lower. Still, that's a lower number than I imagined.
70% of SF households own a car, so still a majority by a long shot [1].
[1] http://www.governing.com/gov-data/car-ownership-numbers-of-v...