Another problem is that driving in SF can can very confusing, draining driver attention. Try to make a left turn onto Market Street on a busy day.
A few months ago, SF made private vehicles turning onto Market Street illegal. Today, biking home, I saw half a dozen cars flout those new laws.
As part of Vision Zero SF, the SFPD have pledged to Focus on the Five (PDF, sorry) "violations that are most frequently cited in collisions with people walking. These violations are"
- Driving at unsafe speed given conditions of roadway
- Red light signal violations
- Failure of driver to yield to pedestrian at a crosswalk
- Failure of driver to yield while making a left or U-turn
- Failure to stop at a STOP sign limit line
I cannot tell you (yeah, yeah, anecdote) how many times I've encountered while riding my bike motorists speeding through the streets of SF as if they were Karl Malden in a 1970s era TV cop show.
So, I'm in perfect agreement with you, ShanghaiBill, that a number of downtown SF city blocks should be turned into pedestrian malls strictly controlled for public transportation only.
As a side note, the first week or so Market Street had SFMTA employees keeping private vehicles from turning onto Market Street was the day public transit drivers and cabbies started racing down Market at over 35 miles per hour and jockeying to beat every. Single. Light. and running them if they couldn't.