found on https://www.facebook.com/pages/Neat-Old-Stuff-and-Yesteryear/154872514719231
Steve let me know that this image showed up on Shorpy 3 years ago, and there are a lot of notes and information gleaned from it
like this observation about the pusher COE behind it:
The cable car is headed for the Powell Street turntable, and if it can't be fixed there the Dodge will most likely have to push it all the way back to the car barn at Washington and Mason Streets. It will be a long push -- mostly uphill.
Cable cars were (and still are) notoriously finicky and tend to go flooey at inconvenient times. This car could have 'lost its grip,' meaning the mechanical device that grips onto the moving subsurface cable that pulls the car along. Alternately, it might have suffered some sort of brake malfunction. Whatever the case, MUNI didn't want any riders on this trip.