How to trip traffic lights

[nrp]

There was a thread here a couple of weeks ago on how to trip traffic lights. A couple of us engineering sorts pursued the subject with the traffic control manufacturers and found out this:

 

The in-the-pavement search coil types should easily be tripped by a M/C. Federal law says so and you should complain to the local traffic engineers if they don't since you are a licensed vehicle. Bicycles are another story but they can be set to even detect these if they don't have carbon fiber rims. However, the local traffic guys will sometimes reduce the sensitivity of the search coil system so they do not trip on adjacent lane traffic.

 

The search coils sense a tiny reduction in inductance (yes, it is a reduction per Lenz's law!) caused by conductive metal adjacent to the coil windings. They are not tripped by the magnetic properties, but rather by the presence of conductive material near a strand or leg of the coil. Maximum sensitivity will be obtained by positioning your wheels directly on top of one longitudinal leg of the windings - not in the center of the coil nor off to one side of any longitudinal leg or strand. It should trip in a few milliseconds, with the rest of the delay being in the traffic signal logic. If you can't see the coils due to pavement rework, you will have to assume where the coil edge is as they are usually 6 feet across. This should be the same as the track of an individual car wheel. In some states they are marked with a bicycle figure on a line.

 

Exploring alternative concepts with their engineering people, there is really no practical active device to enhance sensitivity. The operating frequencies are field selectable and vary from 10 KHz (that's 10,000 Hz) to about 100 KHz depending on the specific needs. The changes in inductance to trip are very small - usually well under a 1% shift. Magnets etc won't work either except to the trivial extent that they can put longitudinal conductive material

close to the coil. Rims should make a pretty effective tripper.

 

So put the rims right over the wires guys........

 

Some of the newer installations instead use a video system mounted on the cantilevered traffic light standard. These have the advantage that they should be sensitive to even a bicycle.

[Argon]

Excellent post-this really helped me to understand these things. I fell for the magnet device to try to help trip these lights, but I never felt they worked very well. Your description of how these sensors work shows why the magnets don't work.

Thanks.

[Peter Collins]

Nie, thanks for the great informational post. I also fell for the magnets.

[JohnJC]

Thanks for doing the research.

 

I do however park right on the wires. I've tried moving around on them, or just sitting there. I've tried the left wire, right wire, and the one that goes accross the lane. My 12ST trips VERY few, if any lights. My CBR trips most lights.

 

I've never had so much trouble, and I have no idea why. Nearly made a left-on-red right in front of a cop the other day. Backed back up over the wire. Next opening in traffic didn't come for a couple of minutes. Light never tripped.

 

Also a sucker for the magnet. It makes NO difference on my ST.

[jjohnson24]

The units get buried too deep and the installers don't calibrate them. Install as received. If you complain a lot they might calibrate them. I just go. I have done it in front of police and not been hasseled.

[John in VA]

Great technical post, but my bike wouldn't trip the traffic lights in my neighborhood even if I laid my RT down on the pavement (no, I haven't tried it, but I have to draw the line somewhere!).

 

If such a gadget installed by the state at great expense can't respond to every licensed and inspected motor vehicle, it forces "unrecognized" vehicles to disobey the signal, thereby compromising traffic safety rather than enhancing it. It is an example of goofy "technology" run amok -- made worse because it's foisted upon us by the state and paid for by taxpayers.

 

/soapbox

 

I look both ways and run the red light when traffic clears. Hopefully, any LEO who sees me will acknowledge how useless the high-tech traffic system is and won't waste a judge's time in court trying to prosecute me.

[gottago]

You engineering types are awesome.

[steve404]

Thanks for the leg work. This adds weight to what I am sure is right, however I just can't yet bring myself to remove the magnet from my center stand.

[ClearwaterBMW]

has anyone EVER had any luck with this?

http://www.greenlightstuff.com/trigger.html

 

greg

[sdpc2]

What always amazed me, is that my K-bike never had a problem tripping the signal. My RT is a 50:50 chance. Go figure.

[Global_Rider]

And when the traffic light don't change, I just treat them as a defective traffic signal.

[ChuckS]

You guys stop for lights????

 

Well when I have to... I just stop. There seems never to be a problem, for me, it just changes, till it does I just wait. Really, I am not in a big hurry (most of the time) and I use that time to let the other bikes catch up..

[Dave McReynolds]

I look both ways and run the red light when traffic clears. Hopefully, any LEO who sees me will acknowledge how useless the high-tech traffic system is and won't waste a judge's time in court trying to prosecute me.

 

Yeah, but how about red light cameras? They've got all the time in the world! Granted, a judge will probably be sympathetic and throw out your ticket....after you've wasted a morning or an afternoon showing up for court.

[ArbyNav]

has anyone EVER had any luck with this?

http://www.greenlightstuff.com/trigger.html

 

greg

 

I worked with the original poster on this, here's the bottom line:

The odds of tripping a light are directly proportional to the mass of conducting metal over the detector loop and how close it is (closer is better)

 

The detector is sensitive enough to pick up motorcycles. The sensitivity is adjustable - the traffic department can make it pick up cycles (unless it is very ancient or badly installed - not very likely).

 

The shape and geometry of the metal on a cycle may improve the odds, because of the effect on the pattern, but that's a marginal effect.

 

There are no devices sold that improve your chances of tripping a light, except for the fact they add conducting or ferrous metals to the bike and a marginal impact on the geometry. Magnets per se do nothing - a block of highly conductive metal with the same shape will probably have the exact same effect.

 

There are no active devices available that will work - I can think of some designs but in the long run they will cause more trouble.

 

In the long term, the best the motorcycling community can do is to make the transportation departments aware of nonresponding vehicle detectors and work with them to adjust the sensitivity. If the traffic engineers don't respond, elevate the problem and if need be, take it to a political level. I think we need to do this. I see more attention to posts on red lights than any other topic - look at the number of views on this (over 400 now) and the earlier post(last I looked it was over 700) vs any other thread. This is at least equal to and probably more irritating than helmet laws and we talk only among ourselves on it. If you belong to an owner or rider association with a legislative group, ask what they do on this.

 

Arby

[KMG_365]

Thanks for the analysis!

 

I've been meaning to call my City again regarding re-upping the sensitivity on a few near me as they seem to have dialed them down again. The problem here is all the Monster trucks and heards of cellphone jabbering soccer moms in their Hummers all over the road with enough steel down low to trip the adjacent turn lanes and back up traffic on the main arteries for a mile or so on surface streets. It seems like someone will complain about the signal timing's effect on traffic flow and they will turn them down in response and voilá--traffic flows more smoothly. Then someone will complain about their bike not tripping the light, and they'll turn them back up temporarily until the next cage driver complains again!

 

And when the traffic light don't change, I just treat them as a defective traffic signal.

This question was posed to a CHP officer for interpretation in a local M/C mag and he said he waits until another vehicle comes to trip the signal . . . yeah riiiiiight!

 

My rationale is as above: from the California vehicle code (I'm paraphrasing): any inoperative or malfunctioning trafic control signal is to be treated as a four-way stop (like a flashing red). So I come to a full stop behind the limit line and proceed when clear to do so. I usually wait until "clear to do so" also means that there are few if any other cars around to get freaked out (including the potential LEO). My argument in front of the judge would be the signals are supposed to register my presence. If they don't they are by definition "malfunctioning" and I merely followed the CVC in the spirit as well as the letter of the law with due regard to my safety and the safety of other drivers, blah, blah, blah. I've got two near me in turn lanes that regularly fail to trip. In the wee hours of the morning I could be waiting for HOURS for another car to happen by--and then they're likely drunk of their A$$ and might well not see me at all--though realistically that's not very likely really with my MotoEquip reflective stickers and Hyperlights!

[David]

In TN, they just codified it with a specific m/c law that says we don't have to wait and can proceed through the red.

[Global_Rider]

And when the traffic lights don't change, I just treat them as a defective traffic signal.

 

This question was posed to a CHP officer for interpretation in a local M/C mag and he said he waits until another vehicle comes to trip the signal . . . yeah riiiiiight!

 

 

My rationale is as above: from the California vehicle code (I'm paraphrasing): any inoperative or malfunctioning trafic control signal is to be treated as a four-way stop (like a flashing red). So I come to a full stop behind the limit line and proceed when clear to do so. I usually wait until "clear to do so" also means that there are few if any other cars around to get freaked out (including the potential LEO). My argument in front of the judge would be the signals are supposed to register my presence. If they don't they are by definition "malfunctioning" and I merely followed the CVC in the spirit as well as the letter of the law with due regard to my safety and the safety of other drivers, blah, blah, blah.

 

I've got two near me in turn lanes that regularly fail to trip. In the wee hours of the morning I could be waiting for HOURS for another car to happen by.

 

Exactly. And you don't have to wait for another car to come by to trigger the lights. I always let the lights cycle through one complete cycle to confirm that they're not picking me up.

 

It is their responsibility to make the lights work. If they can't get them to work for all road vehicles, then I suggest the engineers go back to the drawing board.

[Catbird]

I suppose this may be a different issue, but what about the reported devices that some emergency vehicles (legally) have which "trip" the traffic lights in their favor? Is the existence of these devices totally bogus?

[ClearwaterBMW]

lightwave technology

new lights in a lot of towns have a white light hanging below the red light...... only on when the light is red

they can shine a stick with a certain wavelength of light at it... then it automatically changes the light to green (when it turns the opposite light yellow and red immediately)

hey

you can get a stick yourself

but...... get caught using it......

automatic jail time in most cities

 

greg

[TampaJim]

lightwave technology

new lights in a lot of towns have a white light hanging below the red light...... only on when the light is red

they can shine a stick with a certain wavelength of light at it... then it automatically changes the light to green (when it turns the opposite light yellow and red immediately)

 

I thought the white light was to help traffic cops anywhere in an intersection determine if someone ran a red light

[Husker Red]

Great post, good info on a common question. I like having engineers around!

 

I have a green light trigger magnet on my bike and I felt like it did occasionally help. Of course, at the same time I installed it, I became more careful about stopping over the sensors. Now I learn more and see that the magnet's benefit was almost certainly all in my head, but I prefer to think my $10 POS was a great investment. Maybe ya'll just need to change the batteries on your magnet?

[fnyrt]

Thanks for doing the research.

 

I do however park right on the wires. I've tried moving around on them, or just sitting there. I've tried the left wire, right wire, and the one that goes accross the lane. My 12ST trips VERY few, if any lights. My CBR trips most lights.

try putting the center stand over the trip wire and push it down with your left foot.

[KMG_365]

Hey Husker! I've got some solar-powered deer-whistles that I can sell you REAL cheap--never need batteries!

 

lightwave technology

new lights in a lot of towns have a white light hanging below the red light...... only on when the light is red

they can shine a stick with a certain wavelength of light at it... then it automatically changes the light to green (when it turns the opposite light yellow and red immediately)

 

 

I thought the white light was to help traffic cops anywhere in an intersection determine if someone ran a red light

I'm not familiar with all the devices available everywhere, but we use the Opticom system from 3M for what is termed "signal pre-emption". It is a strobe light mounted high on the vehicle that flashes a VERY rapid pattern of flashes that will trigger a sensor on the signal. Usually the sensor is a very small horizontal "tube on a stick" either above or below the signal. Each vehicle has a unique pattern to the flashing so the signal knows who triggered it and computer records are kept of times and locations for safety and oversight. Some systems even use two different "priority" levels for how fast to change the lights.

 

It's more dangerous to immediately change green to red (imagine the pile-ups! ) or sometimes even red to green (think of pedestrians caught in a cross-walk! ) so the signal timing is modified according to a pre-set algorhythm. The pre-emption software looks at the current state of the signals, from which direction the pre-emption request is coming, the priority level (if applicable) and whether a pedestrian pushed the crossing button and might therefore need time to reach safety and either freezes some lights red, changes others to green to clear traffic or accelerates other greens to yellow then red.

 

Ours works great and makes it much safer than sitting in backed up traffic while someone dies of cardiac arrest, or pushing some poor tourist out into busy cross traffic because they see or hear us coming (though they almost NEVER see us or yield for that matter, but that's a separate rant! ).

 

We used to have a more primitive system that worked audibly with our sirens, but the damn sensors never seemed to work preperly when they did at all and in the corrosive coastal salt-air they were always repairing them. I've never heard of the system you're describing with the "light stick", but perhaps we're talking about the same system.

 

The "lights" used by traffic enforcement are flashes for a camera hooked up to either the traffic signal computers (to catch red-light runners) or stationary radar guns (to catch speeders). In either case they'll take a picture of you in your car in the interesction with the light red with your license plate visible and mail the vehicle's registered owner the ticket (hint, hint). They are pretty easy to beat if you know the tricks and a little "Googling" will give you volumes of reading material.

 

There used to be (and may still be) more primitive pre-emption systems that use simpler and slower strobe patterns (that you can trip by flashing your highbeams rapidly until you randomly hit a pattern) but the manufacturers have had to try to stay ahead of the hackers that were selling units on the internet, and elsewhere. Now, the newer units use complicated patterns with individual I.D.'s that flash 100's of times a second--faster than you'll ever be able to flash your highbeams.

 

Next time you see a fire truck (or LEO squad) rolling "Code 3" (with lights and sirens) look at the top for the rapidly flashing white strobe to know if your area uses them. The newer ones are also usually programmed to shut off separately from the rest of the "code 3 lights" when the vehicle is put in "Park" so that we're not sitting near an intersection working a traffic collision, fire or medical aid and the nearby traffic signal is backing up cross traffic for miles!

[skinny_tom (aka boney)]

Okay, I'll post opposite of Jamie's snake oil thoughts.

 

They work in some places and not others. If you're interested in my experiences and how I came this conclusion, read on;

 

I had a green light magnet thingy on my center stand and wasn't sure that it worked. Now that it's gone, I'm running red left turn signals ALL OVER THE COUNTY because I can't get a green anymore. Yes, it never worked on some lights, and yes I don't need it on others, but the majority of the county operated stop lights picked up my bike before it fell off and don't now. I can suspect an area-wide conspiracy to re-calibrate all the lights around the same time that I lost my magnet, but that seems like a little bit of a reach.

 

It's about the sensitivity of the light trigger. I bought the freakin' thing so I could get the automatic gate to open at work, but it didn't help. Then one day last year it started working. The engineer told me they had recalibrated the sensor mechanism because it wasn't picking up some cars. Again, when the green light thing fell off, I can't get out without using a pass key.

[ClearwaterBMW]

jamie

thanks for telling about how that device work

the one you've described is EXACTLY THE SAME AS THE ONES where we live on the west coast of florida

 

greg