Here is the final evaluation of the On-Street Car Share pilot program that started in August 2014. (Instead of being in parking lots and garages, these car-share pods take up a place on the city streets. There are about 200 of them.)
Summary is that on-street car-share pods are well used, but it’s a nightmare to try to nail down a parking spot for one because of neighborhood opposition to loss of parking and unreliable information from SFMTA about construction.
https://www.sfmta.com/sites/default/files/projects/2017/Carshare_eval_final.pdf