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Old 08-22-05, 10:09 AM   #1
pakole
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What do you do when the light stays red?

Yesterday, I am riding to work, and I was taking a new route. I was at this turning lane with a car behind me, but the light did not recognize I was there. What do you do when a light does not turn on? (I realize later that the light was one of those lights that turn on after straight traffic have gone.)
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Old 08-22-05, 10:28 AM   #2
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In cases where there is a magnetic sensor for a "smart" (read untimed) traffic light and the bike does not trigger the sensor, I go when it is safe to do so. I have two insufficiently sensitive lights on my commute. Most of the time, I can rely on cars to trigger the light, but if there aren't any going my way, I just go anyway. Should I be stopped for it (a real hazard here in Seattle) I don't think I would have any trouble defending my choice. There are rules for how to proceed when a light is broken, which, for my purposes, those lights are.
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Old 08-22-05, 10:30 AM   #3
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First, to clarify the light is actuated by detecting waiting traffic. When it senses a vehicle waiting at one of the entrances to the intersection, the signal stops cross traffic and allows the waiting traffic to proceed. There are ways to improve its chances of detecting your bicycle: http://www.humantransport.org/bicycl...nals/green.htm

However, if that doesn't work, you may wait until it's safe to do so and proceed through the intersection. That light is technically non-functioning and you're allowed to go. If you can't get a gap in the traffic, go over to the cross walk (assuming there is one), hit the walk button, and wait for the walk signal.
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Old 08-22-05, 10:34 AM   #4
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I'll wait for one cycle only.

If I don't trigger the light, I go when it's safe.
I figure by waiting, I've earned the right to go through the red.
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Old 08-22-05, 10:36 AM   #5
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Try lowering your bike till it's almost laid down. If you have a metal frame it should trip the magnet.
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Old 08-22-05, 11:06 AM   #6
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If there's a car behind you, then pull forward so the car can trigger the sensor. Otherwise, if your bike does not trip the sensor you can proceed when safe to do so. The light is considered defective.
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Old 08-22-05, 12:16 PM   #7
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Quote:
Originally Posted by Applehead57
I'll wait for one cycle only.

If I don't trigger the light, I go when it's safe.
I figure by waiting, I've earned the right to go through the red.
Same here.

If it doesn't trigger after one cycle, I just go when safe.

If a car pulls up behind me and I'm not sure I've triggered the light yet, I move forward a bit so that they can trigger it.
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Old 08-22-05, 12:20 PM   #8
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1.Take a couple sips from my water bottle.
2.Look both ways.
3. Run it.
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Old 08-22-05, 12:33 PM   #9
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I use this product...I know it's sort of like an advertisement but it does work:

www.signalsorcerer.com
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Old 08-22-05, 01:20 PM   #10
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Run it.
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Old 08-22-05, 01:28 PM   #11
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If you got and older red light set-up unclip and run your steel cleat over the sensor.
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Old 08-22-05, 04:18 PM   #12
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Run it.
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Old 08-22-05, 04:26 PM   #13
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Um, infra-red doesn't trip inductive sensors. A nice coil 'o' wire will though. Take the AM antenna out of an old radio, ferrite stick and all, that might do it.

I am now interested in how those inductive loops work .... hmmm......... what frequency.......
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Old 08-22-05, 04:26 PM   #14
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I've heard that the best way to trigger them is to put your wheel right on the loop, not in the center.
If it still doesn't trigger, then it's defective. Rules of the road generally say to treat broken lights as though they were 4-way stops. Wait for traffic to clear and go.

Report the incident to your road commission, tell them that it needs adjusting.
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Old 08-22-05, 04:27 PM   #15
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I try to stop right on the sensor, and there's usually enough cars that it doesn't matter anyways. There is one light on my commute though, that tests my patience. It seems like it senses me, the signal for the crosswalk starts flashing 'Dont Walk', after a while though is goes back to 'Walk' without the light ever changing. wtf? Sooo, light traffic: run it, heavy traffic: go push the crosswalk button.
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Old 08-22-05, 04:29 PM   #16
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Do what mommy always said "Look both ways before crossing the street."
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Old 08-22-05, 04:30 PM   #17
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Quote:
Originally Posted by Bikemiker
There is one light on my commute though, that tests my patience. It seems like it senses me, the signal for the crosswalk starts flashing 'Dont Walk', after a while though is goes back to 'Walk' without the light ever changing. wtf? Sooo, light traffic: run it, heavy traffic: go push the crosswalk button.
I've got one that does the same thing. I can get the light to change if I go over and press the ped crosswalk button, but typically I just run it as soon as there's a safe gap. I've never been able to make it go green on the bike.
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Old 08-22-05, 04:40 PM   #18
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Quote:
Originally Posted by myates1980
I use this product...I know it's sort of like an advertisement but it does work:

www.signalsorcerer.com
$20 is a lot of money for a bar magnet. wondermagnet.com will sell you a 2 x 1/2 x 1/4 inch neodynium-ferrite bar magnet (*extrememly* powerful) for six bucks, and it's probably the same thing. Does anyone know if the poles are lengthways or crossways?
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Old 08-22-05, 04:51 PM   #19
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I bring a tent and camp out until it changes. Just kidding! I make certain the way is clear and go.
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Old 08-22-05, 07:18 PM   #20
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Quote:
Originally Posted by lilHinault
Um, infra-red doesn't trip inductive sensors. A nice coil 'o' wire will though. Take the AM antenna out of an old radio, ferrite stick and all, that might do it.

I am now interested in how those inductive loops work .... hmmm......... what frequency.......
An inductive loop simply senses a change in induction by the presence of a conducting material. A rare-earth magnet will trip it through electromagnetic interferance more effectively than an aluminum wheel since the aluminum may not have enough conductive mass to make the sensor stray from it's induction range. The product I mentioned (signal sorcerer) is $20 because it is guaranteed to change the induction enough to change the light and it comes with mounting gear (basically double sided foam carpet tape, and an alcohol cleaning swab). A normal rare-earth magnet will vary in magnetic power and may not work, this product simply HAS the correct power to work properly. Motorcycles have similar problems with changing lights.
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Old 08-22-05, 07:36 PM   #21
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The important point is not that it's magnetic but that it's a conductive mass. Save yourself $20 and go grab some spare bar stock or window weights or something similarly chunky and metal if you're having a problem with inductive sensors.

Better yet, run the light as the law allows and let the appropriate roads or public works department know that until they fix their faulty sensor, you'll continue to proceed through red.
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Old 08-22-05, 08:13 PM   #22
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Quote:
Originally Posted by bostontrevor
The important point is not that it's magnetic but that it's a conductive mass.
Actually you'd need an unwieldy amount of ferrous metal to accomplish changing a light without a magnet. If the bike itself won't change it then a simple lump of metal won't either. A neodymium ferrous permanent magnet with at least 12000 gauss power will work best considering it will only be an inch long by a quarter inch wide.

Traffic lights work off of Faraday's principle of electromagnetic induction. A bar magnet interfering with a weak electromagnet (the loop of wire under the tar in the road) will cause the galvinometer in the sensing unit to read a change and trigger the timing device. I bought the signal sorcerer because where the heck else are you going to find a sufficiently powered neodymium magnet? After much study I now understand the principle but it's still hard to get a hold of a magnet like what they give you in the package...most neodymium magnets you'd find else-where are ceramic and might not work depending on the actual range of magnetic attraction...it's simply a fail-safe idea...it works and it's conveniently available without having to understand Faraday's Law. Now that I know about www.wondermagnets.com I'll use their products from now on...but I just hope that they have the proper power.
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Old 08-22-05, 08:22 PM   #23
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Allow me to quote those more knowledgeable (and educated) than myself:

John S. Allen wrote, of the green light trigger magnet:

"Steve Goodridge has technical material about actuators at http://humantransport.org/bicycledri.../detection.htm

Steve, do you think this thing work, or should work? I am tempted to take an old loudspeaker magnet out to my local actuator loop and see what happens. It seems to me (and I have a degree in electrical engineering) that the magnet would only generate a low-frequency pulse or pair of pulses in the loop, and would have no more effect on the nearly 100 kHz signal sent out by the control box than a non-magnetized chunk of metal the same size -- much smaller than the bicycle's wheels or frame."

Never underestimate the capabilities of magnets, John. When worn on the body in conjunction with proper diet and exercise, they can help you lose weight. Put them under a soft pillow, and you will sleep better at night.

I expect that the manufacturer's instructions tell the cyclist about the best place to stop over the inductive loop. Following these instructions alone probably increase one's success rate enough to earn the company positive user testimonials.

I see no reason why a passive magnet will increase the resonant frequency of a 20-100 KHz inductive loop detector circuit. That's what has to happen in order for the signal to detect the vehicle. Inductive creation of eddy currents inside a conductive object create an opposing magnetic field which reduces the effective inductance of the loop and increases its resonant frequency.

The problem with getting an accurate description of how traffic detectors work stems from the multidisciplinary nature of the invention. A loop detector is used in the civil engineering profession, and civil engineers are usually not experts in things electical. It is built by electronics engineers, but its principle of operation is based on an esoteric area of electromagnetic physics. As a result, the principle of operation is rather separated by those who apply it. I've spoken with application engineers for loop detector manufacturers. Some of them don't fully understand how they really work, and as a result they provide faulty information. Even "How Stuff Works .com " gets it wrong:
http://auto.howstuffworks.com/question234.htm: "...It constantly tests the inductance of the loop in the road, and when the inductance rises, it knows there is a car waiting! " But in a real traffic detector circuit, an increase in inductance (reduction in resonant frequency) is treated as an error condition, not as a positive detection.

Manufacturers of small inductive proximity sensors for industrial and scientific applications generally provide more accurate descriptions of how inductive sensors work, since there may be more variation in the material to be detected.

Lots of unenlightened engineers who have tried to create experiments to test the effects of bikes on loop inductance have used measurement signals too low in frequency to obtain the correct eddy current effect exploited by traffic detectors. This appears to have led some of them to the incorrect conclusion that iron is important. At low frequencies, iron content can in fact raise inductance, but at the higher frequencies used by real detectors, eddy currents dominate to reduce inductance (unless the vehicle is made out of powdered iron glued together with very low conductivity, i.e. ferrite.)

I have an all-aluminum bike as well as an all-steel bike. Both are equally well detected by those signals in town that are adjusted such that they happen to detect bikes. Both bikes reduce the inductance of the loop by carrying eddy currents around the wheels and possibly the frame. It's just a matter of conductive signature; iron content is irrelevant. Traffic engineers who adjust signals to detect bikes in cyclist-friendly communities often just carry a pair of aluminum rims with them for testing.

-Steve Goodridge
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Old 08-22-05, 08:58 PM   #24
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i usually just push the button.

what about those strong magnets from computer hard drives? these magnets are really strong, about 2.5" in length, 1" wide.
hmm i have to go and try it out some times.
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