hairnet

https://www.metacafe.com/watch/828731...raffic_lights/

Check out this video on this simple idea of installing some strong magnets to your bike so lights will change when you go over the sensors as if you were a car.

I'm curious just how much of the metal would be needed, assuming the video could be wrong. It couldn't hurt to try since the magnets suggested in the video are not expensive.

CliftonGK1

There's been a number of studies showing that those mini-magnets don't do squat for a standard induction loop traffic light switch, unfortunately.

Check your local laws regarding "non-functioning" traffic signals. Here in WA, if a light doesn't change through 2 cycles of the opposing traffic, you're allowed to proceed on the red when traffic is clear. I have 2 lights like that on my commute.

hairnet

aw, I was getting excited because there a few lights on my commute that stay green for the opposing traffic FOREVER and there are usually too many cars to run the red.

prathmann

I don't see that adding a small magnet is likely to do anything to help trip the typical inductive loop detectors used to trigger traffic lights.

They operate on the same principle as the metal detectors seen in use by people at beaches who are looking for coins and jewelry buried in the sand. Your bike already has a considerable amount of metal in the rims (closest to the detector) and other parts so a little magnet isn't going to add much. The detectors are generally adjustable in sensitivity and can be turned up to detect bicycles. But there's a rather delicate balance since they shouldn't be too sensitive or they'll trigger based on vehicles in other lanes. I've found the local traffic departments to be pretty good about coming out and readjusting the sensitivity if they're made aware of a problem sensor that's not picking up bicycles.

I find that I'm able to trip most sensors by positioning my Cannondale over either an edge of the loop (for single loop types) or in the center of the loop (for figure-8 or multiple loop types). Laying the bike down over the sensor makes it even more likely to be successful by getting the metal parts of the bike as close as possible to the sensor. Note that any type of metal will work - there's no need for it to ferromagnetic.

cyccommute 

Yup. No magic needed and far more 'scientific' then the guy in the video. From a 'scientific' standpoint, attaching a magnet to a bike, or any other vehicle for that matter, is useless. The magnetic field of any magnet decays with the cube of the distance from the magnet. Unless the magnet is almost on the ground, it has no effect on the induction coil. Find the most sensitive part of the loop and ride your bike directly as large a part of the coil as possible.

For a detailed explanation go here (short version) or here (very detailed version).

steveknight

I had to test it so I took a rare earth magnet rated for 150# and set it right over the wire. nope did nothing.

subclavius

My apartment complex I lived at had a loop sensor on the inside of the gated parking lot. You needed a pass card to get in, but only needed to pull up in your car to get out, because the metal in the car easily triggered the sensors for the gate.

When riding my mid 50's steel cruiser bikes out of the complex, they were usually enough to trigger the loop inductors and open the gate. If I was on an 80's cruiser, road bike, or fixie that was stripped of steel components like derailleurs and kick stands, I would have to stop directly over the sensors and drop the frame to one side so it was almost touching the ground before the gate would open. That trick should work for road lights, as long as you know where the sensor is.

I know several motorcyclists who swear by the magnets, but they insist you use the super-strong rare earth type. I've never tried them since tilting the bike to one side has always worked for me.

CCrew

Most of the new lights are optical anyway.

-R

RobertFrapples

if a light doesn't change through 2 cycles of the opposing traffic

How do you count cycles if the light is not working?

hnsq

Run the red or turn right on red, pull a U-turn and turn right again...

ItsJustMe

Magnets don't work. Putting your rims over the loop properly will work. Steel vs aluminum makes no difference, it just needs to be conductive.

People who get magnets and start having better luck are almost certainly seeing the same effect as people who buy gas mileage gimmicks then see better mileage; they WANT to see an improvement, and they're riding/driving more carefully to try to induce that improvement (like, parking their bike right over the loop).

If you look at how an inductive loop sensor works, and you understand the inverse cube law, you'll see that a magnet on the bottom bracket makes squat difference compared to putting the rim right over the loop.

mr jones

Just about all traffic lights here are done by camera now, but before then, I put my wheels on the center line which triggered the light with no problem...

cyccommute 

Many newer light installations are motion activated. And, perhaps, heavily trafficked intersections. However the camera activated lights are a rarity here in Colorado. The induction loop is still the most common around here. I'd suspect the same is true in most places since the systems are expensive.

cycle16v

How and were exacty are you positioning your bike/wheels to trigger the sensor? Are you putting your bike wheels into one of the cut-out lines or between two lines or in the center of the whole lane?

I haven't had much luck trying to trigger the sensors so I've just resorted to crusing up the sidewalk the last 100 feet or so and hitting the pedestrian crosswalk button and getting back into the lane.

Thanks.

prathmann

This link:
https://www.humantransport.org/bicycl.../detection.htm
has some illustrations. The exact position depends on the type of loop being used at a particular intersection. If it's only a single loop (roughly a square with rounded corners) then placing the wheels right over one of the edges is generally best. Better loops are either figure-8 shape or ones with multiple elements diagonally across the outer square. With these it's better to have your bike in the center of the outer square. Of course the hardest ones are where the intersection has been resurfaced and you can't see the cuts for the loop. Usually it's right near the stop line and I put the bike there and in about the middle of the lane.

But, as I said initially and also in the above link, the detectors are adjustable for sensitivity and if your local traffic department doesn't care about making them bicycle-sensitive they're probably not set right.

CliftonGK1

Poor explanation on my part. For turn lanes it's listed in the RCW as a non-functioning signal if it goes 2 cycles w/o changing. So the "straight only" lanes get a green, but the turn lane doesn't change.

For non-turn lane situations, I either wait for a break in traffic and then just go, or I roll over to the sidewalk and push the pedwalk button.

HardyWeinberg

Yeah I get no result w/ the optical ones. Do motorcycles have that problem?

noglider 

I don't believe we have traffic lights triggered by inductive traffic sensors. Or maybe we do. I do see the inductors embedded in the pavement, but maybe they use a combination of sensing and timing to change the lights. In other words, if no traffic detected in a while, the light eventually changes anyway. I haven't been stuck while cycling. We just started getting some camera-operated lights so maybe we'll bypass the west-coast method.

I'm in NJ, in the NYC metro area, in case you can't tell.

cyccommute 

I know it seems stupid but I've had some luck with only one of these I have to deal with by waving my arms around. You need to be in the middle of the lane near the crosswalk line, however. Doing an S in the lane prior to stopping helps sometimes, too.

cyccommute 

If you see the loops buried in the pavement, the light is likely an induction coil light. Some are also timed. Ride directly over the wires that are going the same way as you are and you'll trip them...most likely, I should say

I have about a 90%+ success rate if I can find the wires.

MikeOnBike

Our local county highway district will come out and recalibrate a light. Just give them a call and within a couple of days they will send someone with a bicycle to tune the sensor.

We also have a law on the books that allows a bicycle to treat a stop sign as a yield and a red light like a stop sign. Sometimes traffic is heavy enough that you really need to trigger the light.

+1 on putting your wheels/frame near the edge of the loop

ian123

lol how come the only way for a cyclist to get through these lights is to make a fool of themselves? either lay your bike over, wave your arms arounds, ride in circles over the sensor, bust out an earth magnet, run to the ped crossing button and come back, or just run the freaking light. i tend to just wait for another car to come and set the sensor off. they need to fix this problem at two of the lights on my commute

HardyWeinberg

There is one red light I routinely have to run, and I don't like doing it 'cause it's across 4 lanes of traffic on a speedway type setup, traffic is ~40mph though the limit is 25, and when I'm at that intersection I have my 4 yr old in a trailer. Anyway, the last 2 times I was there, I managed to trigger the light. I wonder if somebody complained and they adjusted it. I'd think the cars would complain about bikers running the light as much as bikers would complain about being forced to run it.

mr jones

Really? I love the optical/camera; they work great for me!

steveknight

I have one stop with them one side works everytime the other sometimes. but it is pretty food compared to most.
found one turn where there are two spots of paint on the road get my front wheel between them it turns otherwise nope.