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Mythbusting: Green Light Trigger

GReen LIght Trigger traffic lights detect

We recently received a Green Light Trigger unit which is basically two powerful magnets that attach to the underside of your motorcycle and promise to trigger a green light.

Read on and find out if the Green Light Trigger actually works!

Why lights won’t change

Most riders have experienced the frustration of a traffic light that won’t budge off red because it cannot detect their motorcycle which is smaller than a car.

We contacted several state transport departments for their technical advice.

They say these lights are controlled by a induction loop (typically < 0.5 volt ac and < 5 mA)  cut into the pavement.

It creates an electro-magnetic field to detect ferromagnetic metals such as iron, cobalt, nickel, steel and manganese.

Some people erroneously believe these rectangles are actually scales that detract the weight of vehicles and therefore don’t pick up light motorcycles!

For the best possible detection of the metal in your motorcycle, you should position your bike longitudinally right above one of the cut lines or the lead-in cable lines (on the left in the photo below).

GReen LIght Trigger traffic lights detect
Stop over that centre longitudinal cut line

If there are two rectangles cut into the pavement, line up over the centre line for the best effect.

Be aware of oil and diesel spills in the centre of the lane, particularly in the wet. If you pull up on the left or right cut line, be careful of putting your foot down in the slippery centre as you may loose your footing, drop the bike and maybe fall under a vehicle in a side lane.

But here’s the most important part: Don’t move away or continue past the loop! Stay over those lines for the loop to detect your bike.

Also, be aware that lining up over a side cut line or lead-in cable next to a running lane exposes you to the danger of being rear-ended by an errant driver straying out of their lane.

It has also been suggested that if you deploy your side stand directly over a cut line it will help trigger the lights.

We tried it and it doesn’t seem to work, but it may depend on the metal composition of your sidestand. Some modern motorcycles have non-ferromagnetic alloy sidestands to save weight.

Sensitive issue

The transport departments tell us the the sensitivity of the loops is set to detect all vehicles.

However, sensitivity is a delicate balancing act: too low and it won’t pick up a motorcycle or bicycle; too high and it will pick up false readings for cars in adjacent lanes.

If you believe the sensitivity is set too low at a set of lights, you can contact the relevant department in your state or local council area and ask for it to be increased.

Green Light Trigger

But what about this $US30 Green Light Trigger which is basically two powerful neodymium or rare-earth magnets?

The science suggests they could work because the induction loop creates a magnetic effect which should detect other magnets: either attracting or repelling.

I tried it out on my Triumph Street Scrambler and a Kawasaki Versys 1000 test bike which do not trigger a set of lights near my home in western Brisbane.

The Green Light Trigger made no difference.

Believing the sensitivity is just too low, I tried another set of lights where my bike does trigger green.

GReen LIght Trigger traffic lights detect
Green Light Trigger can be attached by the magnet or a cable tie

Instead of using my motorcycle which I know is detected, I placed two of the Green Light Trigger magnets directly on the cut lines. They failed to trigger the lights.

I gave the device to a friend who has complained about lights near his house which don’t detect his bike and he says it worked.

However, RACQ technical officer Steve Spalding is sceptical, believing that the lights may simply have changed as part of the scheduled traffic pattern.

Traffic phasesred light cameras trigger

RACQ Principal Traffic and Safety Engineer Gregory Miszkowycz says if your motorcycle is detected, it won’t necessarily speed up the light change process.

“It just registers a demand for that movement in the traffic controller,” he says.

“If all movements at the intersection have a vehicle waiting, the traffic controller will move through its usual pattern or phases of traffic movements at the intersection.

“There may be three to four movement phases at a typical intersection as all the different movements receive their turn before it returns to the first phase again, which is one complete cycle, usually 60-100 seconds in total. 

“Some intersections at certain times of the day will ‘skip’ certain phases where there are no waiting vehicles. This improves the efficiency of the intersection and reduces delays for motorists by not wasting green time.

“In essence, this speeds up the light change, but only because the traffic controller has skipped other unnecessary phases. 

“There are other intricacies of vehicle detection, like terminating a right turn movement as soon as the queue has gone. It is all to squeeze the most out of the intersections and minimise lost time.”

  1. It is frustrating & dangerous to be stationary through many signal changes in various weather conditions until a larger vehicle joins & activates e.g. right turn arrow.
    I found one of the Motor Writer’s older posts;
    I’ve been proceeding with turns with caution (other traffic & law enforcement) against red lights since I realised that motorbikes weren’t registering their presence at signals, from my first year of riding in 1973 on my RD350 Yamaha, a bike I regret parting with 🙁

  2. Few years ago, I started my project for “ACTIVE Green Light Trigger” device. It is an electronic, DSP based device and a loop antenna, not a magnet. The device receives the signal from the sensor loop in wide frequency range of 10 – 200 kHz, and transmits the specially generated signal back to the sensor. The device reliable works at the height up to 1 meter and above.

    I sells the devices worldwide at
    There are user reviews and some useful information on facebook page

    Hope, it will help.

      1. None, I have carefully studied competitors’ in question patents.
        The published patents for active devices show lack in performance or too complicated to work. Thus, no commercially available devices exist.

        My Active GLT device has a revolutionary approach and based on digital signal processing with advanced state-of-the-art algorithms. It reliable works in wide range of real-world environments using not expensive electronics.

    1. I have used the round fishing magnets with great success for near two years now for near 20 years I have used magnets from pitney bowes mailing printers.
      It is an art and a science to trip what we call magnetic mass indicators. Incidentally when I put two fishing magnets under a HONDA ST1300 POLICE BIKE. I would pull up to a red light, theirs opposite would go yellow,red and mine green almost instantly

  3. From the manufacturer:
    In reading the article what stood out to me was that his friend said it worked on the stubborn lights that normally don’t change once he used it. Then he tried to dismiss it by saying that it may have just because the light cycle started. The light cycle doesn’t start unless something triggers it to start, they aren’t on timers for the majority of the time. So the product started the cycle which means it worked.

    I have also personally tested it multiple times on a bike and also just walking with my product in my hand and it worked like a charm. The explanation for the fact it didn’t work for him is either user error (He mentioned he put the GLT on the line which is actually completely wrong. It doesnt work well on the line , rather than a bit off center from the center of the square or circle.) It actually explains the best way to use it in the instructions. Also very rarely there are lights that are really stubborn and it doesnt work, but that is really uncommon.

    Over the 10 yrs of selling this product we have had mostly all positive feedback and the rare complaints were probably because of one or two defective lights in a town that have issues anyway. We have a 100% money back guarantee policy and have almost never had anyone return them.

    I encourage you or anyone to test the GLT themselves and do it even without a vehicle and you will see its power. Do it late at night when you know the light isnt on a timer. The person that wrote that article should have tested it more thoroughly on several lights and read the instructions on how to use it before writing something after trying it at one light.

  4. When I was riding bicycles a lot I found that stopping on the edge of the loop as you describe was the best way to trigger lights. Can’t say that I have ever had a problem on a motorbike.

  5. From the inventor of Active GLT:
    We have released GLT v4 device:

    The new device is designed for installation under a motorcycle seat and suitable for almost every motorcycle. Our tests show reliable sensors activation at height 1.5 meters above the ground.

    Whats new:
    Better sensitivity and calculation accuracy
    Power controlled transmitter, complied with FCC Part 15
    Flexible antenna for under seat installation

  6. The issue with “active” in the US is it generally needs type acceptance by the FCC to be used legally.

  7. You know what… it’s worth the $30 bucks to give it a shot and I know just the light. You can consistently sit in the left turn for 5-6 cycles of the traffic signals if you’re on a bike (I ride a Shadow 750.) Even creeping forward to give the big rig behind me a chance to trip it didn’t work. I’ll let you guys know if it did the job.

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