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Traffic Activated Stoplights

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Traffic Activated Stoplights

Old 05-02-07, 07:26 PM
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Traffic Activated Stoplights

I was talking to the person in charge of stoplights with the city today. I was complaining about the problem cyclists have with traffic activated lights. He proudly told me that the City was aggressively installing loops for bicycles in the bike lanes. It sounded like news to him that most new bikes don't have enough steel in them to trigger even the bike loops. He did agree that just steel cassettes and chains wouldn't trigger them. He thought they were being "progressive". There are several streets I cross where there is too much traffic to just run the light. What other solutions have people come up with.

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Old 05-02-07, 07:28 PM
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Go up onto the sidewalk and press the "Walk" button then go back down on the road and wait for the light to change.

Pretty sad that that someone in charge of stoplights doesn't know that most bikes sold today don't have much steel in them.
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Old 05-02-07, 07:31 PM
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street lights are activated by magnets... just bike on the square and your bike will be enough to activate it.
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Old 05-02-07, 07:34 PM
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Originally Posted by crd15
street lights are activated by magnets... just bike on the square and your bike will be enough to activate it.
Carbon, aluminum and titanium don't activate magnets. I think that was pretty much the point of the OP.
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Old 05-02-07, 07:36 PM
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Originally Posted by crd15
street lights are activated by magnets... just bike on the square and your bike will be enough to activate it.
You need iron to trigger a magnet, regardless of where you stop.
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Old 05-02-07, 07:37 PM
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Originally Posted by crd15
street lights are activated by magnets... just bike on the square and your bike will be enough to activate it.
Magnets?
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Old 05-02-07, 07:41 PM
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Originally Posted by Sprocket Man
Go up onto the sidewalk and press the "Walk" button then go back down on the road and wait for the light to change.

Pretty sad that that someone in charge of stoplights doesn't know that most bikes sold today don't have much steel in them.
That is ther only solution I have found.
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Old 05-02-07, 07:45 PM
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I have the same problem with my motorcycle at some lights...where I live if you've waited for a reasonable amount of time on a motorcycle or a bicycle...you are allowed to proceed with caution and not be breaking the law....check with your local authorities first....I know they sell magnets for motorcycles that you can attach to the bottom of your bike that will supposedly trip the lights...but there are mixed reviews on whether or not they really work.
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Old 05-02-07, 07:59 PM
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Traffic lights use inductive loops:http://www.howstuffworks.com/question234.htm

These do NOT need steel (or magnets) to be activated, but they do need a certain amount of metal to trigger them. They can be adjusted to detect cyclists but often they are not set so sensitively as sometimes they can be falsely triggered by a car in the next lane over. Some are set so insensitively that even motorcyclists cannot trigger them. A carbon framed bike with carbon wheels is probably not going to trigger any sensor.

Assuming you ride a metal framed bike, you have a few options. The easiest is to get out of the bike lane and position yourself centered in the traffic lane where a car would be trying to trigger the light. The majority of sensors I encounter will be triggered just by doing this. Depending on the type of loop, certain positions work better than others so you may need to experiment if being centered isn't cutting it. If someone pulls up behind you, just stay put and move back over after the light turns so that they don't get all confused. Often someone pulling up behind you will trigger the sensor too.

If that doesn't work, you are legally allowed to run the light. If traffic is dense, this right isn't much help though. As I said before, the sensors can be adjusted but you'll have to contact the county to get that done. It's quite easy from what I've heard so they should be able to take care of it quickly. I need to make this call for a few signals on my way to work.
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Old 05-02-07, 08:05 PM
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Originally Posted by joejack951
. . .Assuming you ride a metal framed bike, you have a few options. . .
Is this true? I ride aluminum - will this work as well?
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Old 05-02-07, 08:06 PM
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great info joejack.
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Old 05-02-07, 08:08 PM
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Originally Posted by Sprocket Man
Go up onto the sidewalk and press the "Walk" button then go back down on the road and wait for the light to change.

Pretty sad that that someone in charge of stoplights doesn't know that most bikes sold today don't have much steel in them.
How about from a left hand turn lane? I think that all you can do is wait for a car or run it.
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Old 05-02-07, 08:11 PM
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Originally Posted by joejack951
Traffic lights use inductive loops:http://www.howstuffworks.com/question234.htm

These do NOT need steel (or magnets) to be activated, but they do need a certain amount of metal to trigger them. They can be adjusted to detect cyclists but often they are not set so sensitively as sometimes they can be falsely triggered by a car in the next lane over. Some are set so insensitively that even motorcyclists cannot trigger them. A carbon framed bike with carbon wheels is probably not going to trigger any sensor.
+1. This I what I thought also.

Sometimes I'll lay my bike on its side down close to the loop. I don't know if it helps, but it seems like it might.
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Old 05-02-07, 08:11 PM
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Originally Posted by RoboCheme
How about from a left hand turn lane? I think that all you can do is wait for a car or run it.
Or you can press the button to cross going forward, then press the button to cross going left. I wouldn't waste my time, though. I'd just ride through the red light.
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Old 05-02-07, 08:12 PM
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Originally Posted by Sprocket Man
Is this true? I ride aluminum - will this work as well?
I don't own a steel bike and trigger lights all the time.
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Old 05-02-07, 08:13 PM
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On Mountain View streets, they'll have a bike symbol painted on the road to show that your bike will activate the sensor. My carbon fiber bike seems to activate the sensors without any problem.
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Old 05-02-07, 08:13 PM
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Originally Posted by RoboCheme
How about from a left hand turn lane? I think that all you can do is wait for a car or run it.
Left turn lanes have the same sensors as the other lanes. They can be triggered the same exact way.
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Old 05-02-07, 08:13 PM
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Originally Posted by joejack951
I don't own a steel bike and trigger lights all the time.
Ah, interesting! I always assumed that only steel would do trigger the sensors. Thanks for the info. Learn something new here every day.
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Old 05-02-07, 08:14 PM
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Originally Posted by joejack951
Traffic lights use inductive loops:http://www.howstuffworks.com/question234.htm

These do NOT need steel (or magnets) to be activated, but they do need a certain amount of metal to trigger them. They can be adjusted to detect cyclists but often they are not set so sensitively as sometimes they can be falsely triggered by a car in the next lane over. Some are set so insensitively that even motorcyclists cannot trigger them. A carbon framed bike with carbon wheels is probably not going to trigger any sensor.
I read that article to say you have to have steel to trigger the inductor. Magnets only work with ferrous metals. That is pretty much the definition. The only ferrous metals on my cf bike are the cassette, chain, the fd cage and a few bolts and nuts. I assume this is also the case with aluminum and titanium bikes, 2 non-ferrous metals.
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Old 05-02-07, 08:22 PM
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Originally Posted by CardiacKid
I read that article to say you have to have steel to trigger the inductor. Magnets only work with ferrous metals. That is pretty much the definition. The only ferrous metals on my cf bike are the cassette, chain, the fd cage and a few bolts and nuts. I assume this is also the case with aluminum and titanium bikes, 2 non-ferrous metals.
That's not what the article said. Non-ferrous materials are not magnetic, but that is totally different from induction. Non-ferrous metals will affect a changing magnetic field, which is how inductive loop sensors work. Same principle that is used in metal detectors. Note they are not called "iron detectors."

Here is an article about this exact topic.

From that article:

There is a common misconception that an object must be ferrous (include iron) to activate a traffic signal loop sensor, or that a ferrous object will perform better. This misconception is fed by the observation that steel cars are detected by standard loop detectors but small aluminum bicycles often, but not always, are not. The belief is rooted in the observation that placing a ferrous core into the center of an inductor coil (such as inside an electromagnet or transformer) affects the inductance of the coil. But in such ferrous-core coil applications, the inductance of the coil is increased by the ferromagnetic effect of the iron, while the typical inductive-loop signal sensors used for traffic signal actuation require the vehicle to cause a decrease in inductance. The iron cores used in typical power inductor applications provide an inductance boost for low frequencies such as 60 Hz. But at higher frequencies, the inductive coupling of eddy currents into the iron core often defeats the inductance boost of the iron. Ferrous inductor components manufactured for high-frequency circuits require a special form of powdered iron called "ferrite" which is designed to minimize its conductivity (especially large-loop conductivity) and thus minimize eddy currents. The steel in cars, by contrast, is highly conductive. Given the high frequencies at which signal detectors operate and the large conductive silhouette of the car, any effect the iron's properties might have to increase the inductance of the coil are overpowered by the induced electrical eddy currents in the vehicle which serve to reduce the inductance of the coil. There are some rare cases where a steel-belted radial with poor loop conductivity positioned in the center of a traffic signal loop can create a net increase in loop inductance, but most traffic signal sensor circuits will either ignore this increase or treat it as an error condition. In short, it is purely the size and net conductivity of an automobile that makes it easier to detect than a bicycle.
After reading that article, it says that the best way for a bike to get detected (if it has metal rims) is to ride directly on the wire.

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Old 05-02-07, 08:27 PM
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Originally Posted by nobrainer440
That's not what the article said. Non-ferrous materials are not magnetic, but that is totally different from induction. Non-ferrous metals will affect a changing magnetic field, which is how inductive loop sensors work. Same principal that is used in metal detectors. Note they are not called "iron detectors."
Any material that will easily conduct a current will work. Any metal meets this requirement.
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Old 05-02-07, 08:32 PM
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Some good news is that when you see a camera on top of the signal pole those are now being used to detect traffic as well and are starting to replace loops as a way of detecting cars / motorcycles / bicycles. Those cameras are not recording, they are used for detection purposes only.
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Old 05-02-07, 08:51 PM
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Originally Posted by joejack951
Any material that will easily conduct a current will work. Any metal meets this requirement.
Carbon fiber will also conduct current (pretty scary actually when your carbon fly rod snaps before a thunderstorm ). It should work also. But placement of the bike over the look is important. I find (not on a carbon bike but aluminum ones) that you have to ride directly over the wire imbedded in the road for nearly the entire length.
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Old 05-02-07, 08:53 PM
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Originally Posted by LowCel
Some good news is that when you see a camera on top of the signal pole those are now being used to detect traffic as well and are starting to replace loops as a way of detecting cars / motorcycles / bicycles. Those cameras are not recording, they are used for detection purposes only.
Some of those motion detectors need to be adjusted to get a target with as small a frontal area as a bicycle. I had one at work that wouldn't detect bicycles. Until they adjusted it, I learned to do a little left hook to present a side view of myself. Larger target. It's been adjusted now.
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Old 05-02-07, 09:04 PM
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Originally Posted by cyccommute
Carbon fiber will also conduct current (pretty scary actually when your carbon fly rod snaps before a thunderstorm ). It should work also. But placement of the bike over the look is important. I find (not on a carbon bike but aluminum ones) that you have to ride directly over the wire imbedded in the road for nearly the entire length.
Thanks. I had always just assumed CF wouldn't conduct current (or not very well at least). Guess I was wrong. How does it compare to steel as a conductor (resistivity value)?
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