Thursday, March 04, 2010

Cycling accidents at Fell and Masonic: the numbers

Given the ongoing hysteria about the allegedly dangerous intersection of Fell and Masonic, for some context let's look at the city's own numbers in the "City of San Francisco 2008 Bicycle Collision Report" of February, 2010 (the MTA website only has an executive summary; if you want the full report, contact the Bicycle Program at ).

The report tells us that there were six "bicycle injury collisions" at Fell and Masonic in 2008---the last year covered by by the report---even though the city redesigned that intersection in September, 2008, installing the first "bicycle and pedestrian only" traffic signal in the city (pages 4, 5). That means there was one injury "collision" involving a cyclist every two months at Fell and Masonic, which is hardly a bloodbath.

According to the long-range numbers for the intersection, 2008 was essentially a normal year: between 2004 and 2008, there were 20 injury collisions involving cyclists at the intersection, an average of four injury accidents a year. In spite of the hysteria about Fell and Masonic whipped up by the SF Bicycle Coalition and BikeNopa, it's fair to conclude that in recent years there has been no big uptick in injury collisions involving cyclists at that intersection.

It will be interesting to see whether the redesigned intersection with the special stoplight has any effect on the number of accidents annually, but we'll have to wait for a future report to find that out.

There's the question of who's responsible for these accidents, motorists or cyclists? Table 13 on page 22 tells us that, where fault is assigned in an injury accident, 48.7% are the fault of motorists and 49.6% are the fault of cyclists.

And what specific violations do cyclists most often commit when they are assigned fault for an accident? Table 15 on page 24 tells us:

83% of the time cyclists were traveling at an "unsafe speed."

86% of the time cyclists were failing "to stop at red light limit line."

96% of the time cyclists were failing "to stop at stop sign limit line."

94% of the time cyclists are riding on the "wrong side of the roadway."

This shows that cyclists don't just annoy the rest of us when they do these things; they also put themselves in danger. Maybe the next report will analyze all the accidents at Fell and Masonic to see where the fault lies. I suspect that, like cycling injury accidents overall, the fault will lie in the 50-50 range, which means that no matter how well the city designs that or any other intersection, some motorists and some cyclists will drive/ride recklessly, and---this bulletin just in---there will be accidents.

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