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My Traffic Light Complaint

Last week I emailed the San Francisco County Transportation Authority and my district Supervisor, Ross Mirkarimi about long red lights at the junction of Page and Divisadero for people traveling on Page. Mr. Mirkarimi forwarded my email on to SFMTA and I eventually got the following reply:

Hi Henry,

This is in regard to your complaint of the long red cycle at Page and Divisadero. We found everything working per timing card but we also found that bicycles were not always being detected. If the bicycle was slightly past the stop bar then the bicycle was not detected and therefore did not get a green light. We have increased the sensitivity of the detector so that the zone of detection is increased. Every bicycle we watched after increasing the sensitivity received its green light.

I am hoping this helps with what you have observed. If not, or if you would like to speak with me directly concerning this intersection or any other please call on my direct line. We appreciate citizen’s input and observations. You will probably be the first to notice a problem on a corridor you travel.

Thanks again for the information. I look forward to hearing from you.

Lauren Green
MTA/DPT Traffic Signal Shop

More on detectors:
We have different types of vehicle detection throughout the City but at Page and Divisadero they are inductive loops that "pick up" metal in cars and bikes. A groove is cut in the asphalt and wire is looped around in about a 6' rectangle area. When a car or bike sits in that loop, it creates an inductance voltage which signals the controller that a vehicle is present. There is usually enough metal in the wheel rims of a bike to trigger the voltage but as you know the light weight bikes are made of non metal and sometimes hard to detect; especially if the bike is not sitting exactly in the detection zone.

I am very happy with the response from Supervisor Mirkarimi and the SFMTA. I don't think I could ask for anything more.


( 4 comments — Leave a comment )
Apr. 21st, 2009 07:38 pm (UTC)
Wow, that's awesome. It's especially cool that they include more information on how it works...
Apr. 21st, 2009 07:55 pm (UTC)
The second part about how it works was taken from a follow-up email where I asked her for details. Still, she was very forthcoming and the emails were informative and helpful.
Apr. 21st, 2009 09:29 pm (UTC)
Oh neat! I learned something, thanks for sharing this. :-)
Apr. 27th, 2009 06:49 pm (UTC)
Pretty sweet. Also: yay you for obeying lights even though you're on a bike! As an occasional car-driver, I really appreciate that.
( 4 comments — Leave a comment )