Instructables

Traffic Light Trigger for your Bike

Not feeling ferrrous enough to trip the induction loops that trigger green lights? No problem - just epoxy a rare earth magnet to your shoe! Inspired by a product marketed to motorcyclists, which is basically a big neodymium magnet to stick under your ride. I thought it might be better to get a slightly smaller magnet closer to the road.
 
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Step 1: Dremel as needed between the lugs of one heel

I always put my right foot down, so I ground out a little extra space on my right heel. Luckily, my Sidis have tall, widely-spaced lugs, so I didn't have to remove much material.

Step 2: Epoxy the magnet, backed with a washer, to the shoe

I used PC-7 heavy-duty epoxy paste and coated the entire magnet, both to protect it and to stick it firmly to the heel. Backing the magnet with a washer helps to focus the magnet field, aiming it down (and not up into your heel, not that it should do anything to you anyhow).

Step 3: Using the magnet to trigger lights

Look for the round or diamond-shaped cuts in the asphalt that show where induction loops are buried at intersections, and set your heel down near the tar lines. Here in Portland, some lights helpfully have a small bike between two hashmarks which you're supposed to line your wheels up with, which is a the perfect spot (and more sensitive, too).
agustafson11 months ago
More images would help with this, but it's such a cool idea.
I tilt my bike over to get the frame closer to the ground. I'm curious how well this small magnet is working.
how about a video
senacharim7 years ago
More Pictures! I'd love to see this in action...
maxwell8 years ago
Cool, have you had luck with this on the lights without a bike sensor?
blacksmith_tb (author)  maxwell8 years ago
Well, they aren't "bike sensors", they're really car sensors, which is why we have to go great lengths to get their attention on our bikes. But the magnet isn't magic - it can't make a light without dectors change. Lights that don't have loops change automatically to control the flow of traffic.
cool, so this is working on the big loops then. Here in LA they have a few spots with a smaller sensor loop in bike lanes. They're still pretty hard to trip, but not as impossible as the big car ones, thought that's what you meant with the stencils on the ground.

I found some interesting reading on this matter, seems a magnet shouldn't actually do much, but putting the rims in the right spot will, unless you've got carbon rims

http://bicycleuniverse.info/transpo/triggering-signals.html

http://www.humantransport.org/bicycledriving/library/signals/detection.htm