Tripping the light
 

There are various traffic signals with sensors around town. With my carbon bike, I have not been able to trip any of the signals. My guess that I'm not stepping on the sensor in the correct place. I usually end up stopping, and then proceeding with caution through the (usually deserted) intersection. But a cop would probably ticket such a move.

Here is one of the sensors....where do you step on it and how long does it take to trip it.

The standard traffic light sensor is magnetic, not sensitive to pressure. Your carbon fiber bike may not have enough ferrous metal to trigger it. :(

My steel bike has not enough metal to trigger it ....*sigh*

I had a huge Harley that wouldnt trip them.
There are laws in some states that allow you to
proceed after a reasonable amount of time.

Even all-steel bikes don't have enough metal in them ususally...

I think you can talk your way out of a ticket, if not with the cop, then in the court for sure. You have the rights and responsibilities of a vehicle operator, and the light is clearly malfunctioning from your perspective, hence you're free to ignore it and just proceed (with caution, of course).

A trick on a motorcycle is to put down the side stand. That usually (but not always) works for me.

You might consider putting a steel kickstand on your bike.

There are threads that discuss how to position your bike -- if it has metal in it. In general, position the wheel over the exposed trigger lines -- preferably inside the circles. Some lights work reliably with this technique, and others don't work at all. Some lights have long delays even if they do trigger, so its useful to time the light. Apparently even a small amount of metal can trigger the lights if its close to the trip wires. For people on carbon frame bikes, I wonder if you could carry a small 6" wrench on a string and drop it along the wire. Then haul it up when you see the side yellows switching.

The real problem at a lot of lights is that the lines have been paved over. Still others you can see lines -- lots of them! -- with no clue which ones are the current active set.

Supposedly they can set them up to be sensitive enough to be triggered by a steel bike (double loop or figure 8 of cable, I think) but there are a couple on one of my routes that have a bike symbol painted on the pavement, but where nothing happens when I stop over them. I'd be just as happy if they moved the pedestrians' button closer to where I stop so I could reach that.

Several months ago, I posted this question to the local bike club and somebody replied that you just step on a WHITE X with your cleat and that changes the light.

The X's are on the right most part of the lane and were in the wrong place esp if you're turning left. My cleat did nothing.

Maybe I should do a CYA move and call the city...then if a cop stops me, I can proved that I did report the problem.

I have read that putting loops of copper wire inside of your rims can help. Apparently the ends need to be electrically connected into loops to be effective though. I ride bikes with plenty of steel, so this has not been a problem for me. The one light that I ever really have to trigger on my own works great by just stepping off my bike and laying it down sideways on top of the sensing loop.

If you call the city and explain the problem, you should be able to get them to recalibrate the light sensors to be sensitive enough to be tripped by a steel-frame bike.

To the OP: the two round loops are the sensors. the other cuts are just troughs for wiring to run from the sensors to the control box.

I read somewhere that hopping off your bike and laying it on the ground for a couple of seconds might do the trick. :) Unless you have a carbon bike... :D

Attached is the picture of the other sensor that does not trip. Yea laying the bike on the ground is probably just as funny as trying to stamp on a white X ------> probably trips a hidden camera to broadcast your efforts to the nearest bar :)

Someone posted a link to an article recently about tripping the sensors, which obviously no-one read. The gist of the article was that the metal does not have to be ferrous, (alloy rims will work) but must form an electrically complete loop (ie its the wheels, not the frame that counts) and will function best when placed with its plane parallel to and on top of one of the cuts that form the loop. The article also said that some detectors do need to have their sensitivity adjusted to detect bikes.

Here in Tennessee that would be consdered a malfunctioning signal and we are allowed by law to basically proceed as if it was a stop sign. You may want to check you state laws for the same thing.

Urban Bikers tricks and tips mentions a magnet to trip the lights.
http://www.amazon.com/gp/product/096...lance&n=283155

Hey, cool -- it even got reviewed by one of our forum "celebrities"! (one star). It sounds like there's a lot of bad advice in there ... but it got 3 stars -- not bad by Amazon standards.

:-) I didn't look through the reviews... but the magnet sounds okay.

Taken from here: http://bicycleuniverse.info/transpo/...g-signals.html

"I read your article on triggering traffic signals with a bicycle and would like to tell you a few facts about vehicle detectors as I am a designer of these units. Firstly, magnets have no effect at all on loop detectors (unless of course the magnet is so big that it acts more like a big mass of metal.) If you want to trigger the traffic lights with 100% certainty, simply get off the bike and lay the front wheel of the cycle flat over the loop towards one corner for a second or two. The rim of a cycle wheel acts like a big short circuited turn of wire and used in this way will produce a bigger signal than most automobiles do. The reason for this is that you can place your wheel flat on the ground so that it is about 10 x closer to the loop than most automobiles can reach."

Also see this article, and the links he gives at the end: http://www.bikexprt.com/bicycle/actuator.htm

Remember to dance the funky chicken nekkid

I used to be the field manager for a company that installed vehicle detectors. Let me add my .02 worth.

Detectors will pick up non-ferrous metal, however, ferrous metal is detected much more easily.

It doesn't matter the shape of the metal being detected, a cube, sheet or hoop all look the same to a detector. It's mass that's important, the metal of the vehicle adds to the force of the magnetic field created by detector. This is done by intersecting the lines of the magnetic feild created by the detector so mass the important factor. The more magnetic lines you intersect, the better. That's why laying a bike over the loop will work better than a standing bike.

The magnet idea is ridiculous. A magnet will not create a difference in the magnetic feild of the detector loop that will cause a difference in the current through the loop, which is what the electronics of the sensor actually detect.

Here is a very good article on the subject.
http://www.hgsc.bcm.tmc.edu/~havlak/...detectors.text

SB

Actually I don't think it is magnetic but sensitive to things that conduct electricity (metal in particular). It measures induction. I find if I can get my rims over the wires they trigger almost all lights. (bet you didn't know there were theramins all over town in the pavement huh? They should put a speaker next to the lane so as the pitch rose you knew you were on the sensor :) ).

Thats right. Even aluminum rims and/or a crank will be enough for a properly tuned sensor. I did a test in my hood and carried my front wheel to a couple of intersections and sure enough just the front wheel alone standing on tire over center wire of triple wire sensor was enough to trigger.

If your aluminim rims and crank are not triggering the sensor and you have bike in proper position and you wait for traffic control system to change light (it may take a couple minutes after you trigger or it may require more than one vehicle to be in line) and it still doesn't work then you really should call your public works or traffic dept. and file a friendly request to have the sensor tuned properly.

Al

VR, I think parking your rear hub over the sweet spots at the sensors would be the most advantageous when you are on your CF bike.

My rule of thumb for Seattle traffic sensors: 15 seconds to trigger the little red hand says 'stop' starts flashing at the intersection signal, or I proceed (once clear) under the assumption the bike will not trigger the sensors. At intersections facing off at right turn only lights, i often sneek in past the last car opposing, if I can see the light above is still green for them....I don't think this is legal in WA however...

I recommend most urban bikers get good at reading the traffic lights and walk signals that DON'T face their travel direction...

This may be how they are set up in Seattle, but I know that in Tempe-Arizona and surrounding cities that the walking man symbol may take up to 2min to start flashing red after sensor is triggered whether in car or on bike. 2min can seem like forever when waiting.

Al

that's why I only wait 15 seconds, Al.