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The Slow Lane: The City's Anecdotal and Statistical Traffic Studies Collide 

Tuesday, Nov 11 2014
Comments (1)

Anecdotally, traffic is bloody awful in this city and getting worse every day. Anecdotally, the roads have never been so clogged and it's never been easier to leap from rooftop to rooftop of the legions of vehicles navigating San Francisco at a glacial pace.

Anecdotal evidence is hard to counter. But what statistical evidence does exist flies in the face of your well-worn anecdotes.

Bay Bridge auto counts for October indicate around 128,000 cars heading into San Francisco on a daily basis. That is 3,000 to 5,000 more cars than in recent years — but fewer cars than in 2005. The number of vehicles heading into town via the Golden Gate Bridge topped 40 million in the fiscal year concluding in June. That's more than either of the last two years — but fewer than fiscal 2010 and fewer than any year between 1985 and 2001.

So, it's busy. But it has been busier.

The San Francisco County Transportation Authority has undertaken detailed analyses of congestion and average vehicle speeds along major San Francisco corridors. Counterintuitively for anyone who traverses this city on a daily basis, traffic counts are down and average speed is up.

The CTA focused on 15 intersections for its p.m. peak traffic count. Between 2009 and 2014, the observed vehicle count dropped on 13 of them (Columbus and Broadway grew 5 percent more congested and Fell and Van Ness held steady).

Similarly, average vehicle speed increased between 2009 and 2013 on eight of 12 observed thoroughfares during both morning and evening commuting hours.

These results surprised CTA planners, too. Anecdotally, one could explain away rosy San Francisco traffic count numbers due to bottlenecks on feeder roads, which mean fewer vehicles clogging the observed areas. The CTA is eyeballing a handful of roads, but not the streets surrounding them.

But the data does not bear this out: The combination of fewer counted vehicles and higher speeds indicates less demand for the city's roadways rather than more, per CTA traffic planner Dan Tischler. Believe it or not, things may be getting better.

And yet, your anecdotal nightmares on this city's highways and byways aren't invalidated by this statistical analysis. There are, after all, far more than 12 major roads and 15 intersections in this city. And, CTA officials concede, there's much, much more construction taking place in our rapidly transforming city than in years past. While spot checks may indicate smoother sailing overall for commuters, construction can lead to spectacular delays in pockets across the city.

Altruistic commuters trapped in gridlock along these routes can take some comfort: There are other people, not far off, having a much better time.

About The Author

Joe Eskenazi

Joe Eskenazi

Joe Eskenazi was born in San Francisco, raised in the Bay Area, and attended U.C. Berkeley. He never left. "Your humble narrator" was a staff writer and columnist for SF Weekly from 2007 to 2015. He resides in the Excelsior with his wife, 4.3 miles from his birthplace and 5,474 from hers.


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