
Browsing around for bike-related goodies today, we came across this brilliant example of proletariat problem-solving in the name of an improved urban cycling experience. They call it the Traffic Loop Sensor Activator, or sometimes U.S. Patent #7,432,827--we call it a nice alternative to sweating for minutes at a time in the midst of high-speed traffic, waiting for a green light that never comes.
The gadget, depicted above, directly triggers the inductive sensors embedded in the roadway at many intersections, by creating a strong but short-lived magnetic field that simulates the presence of a much larger conductor--like the steel body of a car. Note that it's not an always-on kind of deal; the cyclist must press a button to activate it when centered over the telltale two-rectangle groove of the induction sensor coil, but it's a heck of a lot better than hoping for a car to come along and rescue you, or risk running a red light with an excuse no dedicated motorist is going to believe.

Obviously clunky and big, we'd love to see a sleeker version integrated into a few of the growing multitude of "urban commuter" bikes being trotted out lately, if only out of pure self-interest. We've gotta wonder, though, what the prototype testing looked like for this one. Late night intersection inspections maybe?
>>Read more about it, and get directions for building your own (if you're nerdy enough)<<
Comments
Just tape a large magnet to the bottom. All you have to do is change the EM field around the inductor that senses cars, and a simple magnet will do the job nicely. It's an old motorcyclist's trick.
Thanks for the nice comments.
Yes, there were many late night missions to certain obstinate intersections.
One thing I want to clear up....the device does not just make a strong, short-lived magnetic field; it scans around to find the frequency of the loop sensor, itself, and transmits back a mag field at or near that frequency. The frequency is key.
And, yes, you're seeing a clunky prototype. It can be made much smaller.
This is unreal!! But I agree it does have a purpose.
I find this to be generally unneeded. I've done tests with both aluminum and steel rims on traditional stoplight sensors at several city yards on several types of systems. On properly installed systems, a bike tire will work just as well as a car at triggering the sensor.
Simply place the tire inline with the direction of the sensor wire (tangential to the sensor loop in the road). The wheel sets up a field that will trigger the sensor. Believe it or not, it actually works better for aluminum rims.
I hardly ever seem to have a problem with getting "forgotten" by the sensors -- maybe twice a year. I either run it or go down the crosswalk toward the crosswalk buttons.
How long is the signal generated? I ask because some traffic signals require that a vehicle be sensed for some number of seconds before triggering. For example, a car that stops at the signal and then quickly makes a right turn on red won't be enough to change the signal over.
BTW, Chris has it spot-on. The vast majority of loop sensors can be triggered, even on a full-carbon-frame bike, by sitting right on top of one of the loop wires. You don't have to be magnetic (ferrous), just conductive, and even lightweight aluminum-rim wheels fit the bill.
Once again, an answer looking for a question. ;-)
Yea its very clunky and ugly to look at, also I would never risk leaving my bike tied outside because someone could steal the electronic transmitter.
These are illegal in almost every state.
Forget that. There's nothing I hate more than people riding there bike like it's a car. GET OFF THE ROAD.
Seems like overkill. You could probably just attach a neodymium magnet to the bottom of your bike and get the same result for $3.
I've never had to do more than simply lower my bike down toward the road so that there's more frame parallel to the sensor. If there are 3 dots in a row about 18 inches long, stop your bike over them - it's a more sensitive part of the sensor made for bikes.
I have an Earth magnet attached to the bottom of my bike, just under the kickstand mount, and it trips the sensor instantly when I roll over it. It's about the size of a 50 cent piece, but super strong!
mngrif is right. I had one on my motorcycle many years ago, so I also put one on my bicycle. Never again will I have to wait for a car to come up behind me to change the traffic light to green so I can go.
Looks like the bandwidth surge of digg knocked out the pics..
Yea it may be heavy but you could use the battery for lights or even attach a generator... that would be epic at a critical mass meet up.
This technology has existed for YEARS for motorcycles, already.
I ride a motorcycle that weighs about 300 lbs and have problems all the time with sensors. Sometimes I just get frustrated and walk over to the crosswalk buttons, which isn't recommended in case the light does change.
Save yourself a metric ton of money and simply invest in a pair of high-strength magnets, you can get a pair of small magnets that can be secured between the spokes of your front and rear tires (they're about 1/2" across, cubic in shape) and you will never have a problem with this again. You don't need some ridiculous magnetic field detection technology, cars certainly don't run anything so complex for the sole purpose of triggering sensors, so why would you?
Chris: I can't count the times I've been stuck in the left turn lane on my motorcycle, while watching the light cycle back and forth 3 times w/o a green arrow. The whole time I've been rolling the bike back and forth across the sensor area. If it's the middle of the night and there are no cars the light's simply not going to change at some intersections. You can't tell me that 15lbs of metal is going to have better results than 460lb of metal. It just depends how many times the street has been asphalted over.
They have sold these for motorcycles since the 80's
Isn't the ability to run red lights one of the great advantages of bicycling?
you mean "adventures", not "advantages"
I hear that if your motorcycle isn't detected, kill the engine, then start it up again. The flux generated by the starter motor is enough to trigger the loop. Or so I've heard.
Bunk. See http://www.humantransport.org/bicycledriving/library/signals/detection.htm Magnets don't work, neither should this, I suspect, and parking with your aluminum wheels over the detector works fine.