Tuesday, October 26

Night Traffic Cameras

Signal Operating Traffic Cameras are Tricky
There are a lot of traffic signal cameras around North Texas. They seem to be the signal changing mechanism of choice for almost all new signals. I reported here and here how a cyclist can use knowledge of how they work to make those pesky traffic signals turn green.

Well, it appears there may be another factor at play – our lights when it is dark. As noted, the traffic cameras do not use infrared to detect vehicles in their zone of interest. They use visible light. As a result, as long as the sensitivity is set appropriately, they’ll detect a cyclist “in the zone”  – at least during the day.

At night, it is another matter. I always figured that the headlight of a cyclist is plenty bright to trigger the signal, but then I started to encounter lights that would not change for me in the predawn darkness, but WOULD change during daylight hours. I tried taking my blinky headlight off and pointing it directly at the camera. No joy. What DID work was simply turning the blinky headlight on steady mode, and lighting up the flamethrower for extra effect before I rolled up to the intersection camera field of interest. I have not seen anything on the internet about the specific changing algorithm used by the cameras, but it appears they may depend on a light staying lit for longer than a cyclist’s blinky headlight, so that the lights are not triggered by extraneous brief flashes of light. I’d LOVE it if someone out there can verify this, but in the meantime, my suggestion is “make sure your headlight is on steady mode when coming up to a traffic signal activated by a camera. Stop a bit further back from the stop line than usual, because your headlight may not be high enough to be in the camera’s detection zone.” If you get bored, take the light off and point it at the camera; in steady mode. Certainly, this advice cannot hurt and may improve your ability to change traffic signals in the dark. I really DON’T like signals that won’t trigger for me!

Do Traffic Signals Operated by Cameras Trigger Better for YOU When Your Lights are Steady and Not Blinking?

4 comments:

John Romeo Alpha said...

Steve, check out the section in this document on the differences between day and night (Day Versus Night Operation, p.9). It sounds like you would support the paper's concluding sentence: "manufacturers are also encouraged to improve their night operation algorithms in order to reduce variation in response to vehicle headlight reflections."
http://www.ltrc.lsu.edu/TRB_82/TRB2003-002367.pdf

Chandra said...

I have my battery operated ones on non-blinking mode so I don't annoy other drivers, especially those going in the opposite direction. I have two tail lights, one of which is in the blinking mode, in hopes of alerting those approaching me from behind.

I don't know the ins and outs of how the blinking v. non-blinking affects the traffic signals and I am going to read JRA's link. In addition, I might do some testing of my own.

Peace :)

RANTWICK said...

You, my friend, have some big ass lights.

Steve A said...

JRA found an interesting article and I'll study it further. The authors did not test the different characteristics of bikes which approach a light slower and cars don't blink their lights. The reflection aspect and detection/activation timing are interesting. All of it suggests DIVDS operators often do not know WHAT their systems will do with either a vehicularly operating bike, or one being operated in a more common fashion.

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