RLGL or red light/green light

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The next time you’re sitting at a red light that looks as though it will never go green, refer back to this:

On-demand signals use what they call “induction loop vehicle detectors” to sense when a vehicle is waiting at a light. These detectors are essentially metal detectors embedded into the pavement. They work by sensing changes in an electromagnetic field and have nothing to do with the weight of the vehicle. You can often see evidence of loop detectors as lines cut into the road surface just behind the crosswalk. Wire sensors are embedded in these cut lines, and it’s possible to trigger a light by placing your bicycle wheels directly on top of one of the wires to disrupt the magnetic field. Some sensors seem to be more sensitive than others; in those cases where the light isn’t initially triggered, I’ve had some success by leaning my bike over toward the inside of the detector loop. In cases where there are two side-by-side loops, lining up over the center where the two loops meet doubles your chances of triggering the light.


Well played, sir. Well played indeed.

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About big jonny

The man, the legend. The guy who started it all back in the Year of Our Lord Beer, 2000, with a couple of pages worth of idiotic ranting hardcoded on some random porn site that would host anything you uploaded, a book called HTML for Dummies (which was completely appropriate), a bad attitude (which hasn’t much changed), and a Dell desktop running Win95 with 64 mgs of ram and a six gig hard drive. Those were the days. Then he went to law school. Go figure. Flagstaff, Arizona, USA

10 Replies to “RLGL or red light/green light”

  1. Queen City Bike, an advocacy group here in Cincinnati, got the “hot spots” of several of these induction loop vehicle detectors along common commuter routes marked with an X so you know where to roll up on it. Proof of a good grass roots effort that can pay off.

  2. you can also glue a small magnet under the bottom bracket if this is a common problem for you

  3. …i believe it’s now mandatory to install ‘bike sensors’ when building new infrastructure here in california & while ‘bike coalitions’ strive to speed up the retrofitting of such everywhere else viable, there seems to be a lotta footdragging in places…

    …undoubtedly finances play a big part but at what cost to safety ???…

  4. That’s all fine and great, but what about the signals that do not use induction loop interference? Here in the 303 the DOT has replaced many lights that use image sensors. Most of these are not calibrated to sense a bicyclist. Coupled to this, when the lights were upgraded, the DOT took out curbside push-button sensors. These were on several bike route, most noticeably around city park. Now, instead of being able to trigger the light from the lane, cyclists has to dismount and/or ride onto the sidewalk to trigger the crosswalk signal. I’ve sent several emails to city and state agencies asking about the inconsistencies, with naught a single reply. In my opinion, the new signals (supposedly more efficient) only make intersections more dangerous to cyclists. At one particular intersection, car-bike collisions increased 700% over last year, before the new signals were installed, going from 0 to 7. Did I mention this is on a street with a marked bike lane that goes into a park? More evidence of the ignorance of traffic engineers to entire spectrum of road users.

  5. I was stuck at a light while on my way to the shootout in Tucson, and the thing wouldn’t change. Five minutes and not a single car, so I ran the red, only to have an under-cover cop pull me over and give me the following tickets:
    Left of center
    Running a red light
    Under vehicle decription, the cop wrote, “black road bike.” It ended up costing me $600 thanks to the lovely judge Dawes. I was a broke college kid at the time and employee at fairwheel bikes. America!

  6. It is sad that EcoVelo is no longer being updated. I thought it quite a classy blog. It isn’t DC, but not everything has to be, right?

  7. AZ law allows you to pass thru a signal that appears to not be functioning
    The driver of a vehicle approaching an intersection that has an official traffic control signal that is inoperative shall bring the vehicle to a complete stop before entering the intersection and may proceed with caution only when it is safe to do so.

  8. …@ training wheels…unfortunate & somewhat ironic, ya ???…
    …originally, ‘dawes’ is an old-time english bicycle brand featuring both racing & touring models…

  9. ‘is’, ‘was’, i don’t know, a poor choice of ‘english’ words…
    …my bad…

    …it’s very early in the morning, 4:15am, left coast time…

  10. They said a few years ago that it would help with motorcycles to throw a couple neodymium [sp] magnets underneath. I have used a truck hitch to open gates to gated communities that have a open walkway but require a keycard or code to drive in using the same type of inductive loop sensor (in through the out door, haha). However, carrying that heavy chunk of steel is not my idea of fun.