According to the California Bicycle Coalition, as the number of trips made by bicycle in San Francisco has nearly doubled in the past seven years, the number of collisions involving cyclists has also doubled. The visibility effect seen in other major bike-friendly cities apparently hasn't held true in San Francisco.
In Portland, Oregon, where bike ridership has tripled since the city committed to bicycle infrastructure improvements years ago, the number of collisions involving cyclists has stayed relatively even. Bike activists attribute stats like this to a "safety in numbers" mentality: more bikers leads to more visibility leads to more awareness among drivers. So why is the opposite happening in San Francisco? The Cal Bike Coalition blames it on the infamous injunction that stalled infrastructure improvements for years:
After four years of an injunction against new bike infrastructure imposed as punishment for violating a misguided environmental law (which we helped to change), San Francisco is playing catch-up, trying to accommodate the demand for safe bicycling. Cities like New York on the other hand are designing infrastructure ahead of the curve of people riding bikes. Each has their visionary goal: New York plans to have a city with zero fatalities or serious injuries caused by car crashes on the streets within 10 years, San Francisco plans for 20% of trips to be made by bike by 2020.
So, even as San Francisco pushes it's goal of getting more cyclists out on the city streets, the city isn't necessarily on pace with bike lanes and necessary infrastructure to keep those riders safe.
While you, cautious cyclist, await the next round of bicycle infrastructure improvements, you might also want to consider this map of 307 bicycle crashes that occurred in San Francisco in 2012 and 2013 (and those are just the ones that were reported):
Click through here for an interactive version, complete with crash frequency data and street views of the incident sites.YouAreHere.cc)