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  1. #1
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    Stoplight Triggering

    At a stoplight that changes only when a vehicle triggers the magnetic sensor wire circles in the pavement, the large-diameter circles designed to detect cars typically don't read me standing astride my bike, so I never get a green light.

    If I lay my bike down flat, so the metallic frame covers a substantial portion of the circle only a few inches above the pavement, then the magnetic sensor usually does read it and I get my green light.

    I'm not "into" the road bike community enough to know: is this a well-known trick I've merely re-discovered? Or is this something I should spread around for others' convenience?

  2. #2
    IdontShootPeopleAnyMore
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    whats more dangerous laying down in the middle of the road or running a red light?
    What mountain bike forum do pirates use? .....



    MTB-arrrrrrrrrrrrrrr

  3. #3
    Ovaries on the Outside
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    Quote Originally Posted by DriveByBikeShooting
    whats more dangerous laying down in the middle of the road or running a red light?
    What the ****? Is laying your bike down at a red light dangerous at all? You do realize that one isn't lying down with the bike....

    To OP- laying down a bike on a magnetic strip is proper form. Sometimes they don't trigger, so burn the light. I try to avoid burning reds/stops because I think it is a bad example for cycling.

  4. #4
    Squeaky Wheel
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    If your wheel alone won't trigger the light, call your local road department and ask them to adjust the sensitivity. Around here, all the detector loops have a little white "X" painted where you should put your front wheel for reliable detection. I've see the local road department techs adjusting the loops...they use a bike wheel.

  5. #5
    weirdo
    Reputation: rodar y rodar's Avatar
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    I don`t think sensitivity is normally as big a problem as being in the exact right place. I`m also guessing that laying the bike over sometimes works because in the process it ends up directly over the sensors at some point rather than because the frame is closer to the coils. Of course, I could be wrong about that . The nice white Xs sure would be sweet. Our intersections are usually so patched, repaved, and funky looking that there`s normally no way to tell just where the sensors are.

    All I can say for sure is that you`re battling a familiar issue wth the triggering signals thing. It`s an eternal problem for most of us, so you aren`t alone.

    And welcome, Vijeta.
    Recalculating....

  6. #6
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    Just ride up to the signal pole and push the pedestrian crossing button

    There are no "sensors" in the pavement, just wires run in conduit, usually in rectangular shape. When there is enough mass of metal over the wire it alters the electromagnetic field telling the signal controller that it's time to change the light. Standard loops for cars are fairly big and the rectangular shape would most likely completely encompass a person on a bike. If you can tell where the conduit/wire runs, usually by a patch or saw cuts in the pavement, you are better off trying to be on the outer edge and directly over one of the runs of conduit/wire than smack dab in the middle. They are starting to put in smaller loops and loops of different configurations that will detect a bike much easier, but obveously those won't be everywhere.

  7. #7
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    In Tempe they have started putting bicycle buttons next to the curb so you just stay in the street and can push the button. It's quite nice! If there isn't one I just ride up on the sidewalk and hit the pedestrian button. I only run a light if nobody is anywhere around to see and I have been waiting too long, don't want to give any more fuel to the angry motorists when they decide to complain about cyclists in their area.

  8. #8
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    Recently installed or newly paved intersections with obvious octagonal wire pickup loops at the two intersections I have trouble with.

    Both have triggerd once each when I approached the stop line since they were installed. I suspect the loops are on some timed, decreasing signal trigger, algorithm, so after 10 minutes without changing my bike is good enough. I have tried every spot on the two forward loops and there has been no joy in Mudville. I have a steel frame and a big ol' cup and cone BB to trigger with. One state (Utah?) allows you to proceed after stopping and waiting for a break in traffic and Indiana considered doing the same. No luck. They do allow treating it as a stop sign if it is malfunctioning. So If after the usual trigger time no cars have lined up behind or opposite ot trigger the light, I will treat it as malfunctioning, as it is from my perspective. May not stop a ticket, but maybe it will. They don't have pedestrian buttons, and one doesn't even have crosswalks! Very lame.

    The lay the bike down technique is intriguing. Next time I am the sole transportation device awaiting a light change I will try it. Nothing to lose if it doesn't do the trick. I'm standing around anyway,

  9. #9
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    Many of the traffic lights in my area won’t even detect my Harley so I end up making a couple different turns to approach from a different direction or using the pedestrian crossing devices to trigger the lights.

  10. #10
    ~Disc~Golf~
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    Quote Originally Posted by haager
    ...

    There are no "sensors" in the pavement, just wires run in conduit, usually in rectangular shape.
    Quote Originally Posted by haager
    When there is enough mass of metal over the wire it alters the electromagnetic field telling the signal controller that it's time to change the light. ...
    hmmm.
    Honestly... ahh I give up

  11. #11
    weirdo
    Reputation: rodar y rodar's Avatar
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    Quote Originally Posted by highdelll
    hmmm.
    Yup, senseless.
    That`s okay, though.
    Recalculating....

  12. #12
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    Yes, wires CAN be sensors and the curent in them, the signal. The poster got his point across regardless of his definition of 'sensor'. Good enough.

  13. #13
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    Amen.

    What if you are a carbon fiber nut though- horseshoes on a string?




    .

  14. #14
    ~Disc~Golf~
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    Quote Originally Posted by grandsalmon
    Amen.

    What if you are a carbon fiber nut though- horseshoes on a string?




    .
    I've heard that a neodymium magnet epoxied to your sole will werk - never tried it though
    Honestly... ahh I give up

  15. #15
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    Quote Originally Posted by highdelll
    I've heard that a neodymium magnet epoxied to your sole will werk - never tried it though
    Don't get carried away with the Gauss, or you might stick to Manhole covers and grates!

    How ignominious (how often do you get to use THAT word?) would that be?

  16. #16
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    Quote Originally Posted by haager
    There are no "sensors" in the pavement, just wires run in conduit, usually in rectangular shape. When there is enough mass of metal over the wire it alters the electromagnetic field telling the signal controller that it's time to change the light.
    ...er well, there is a controller in the signal cabinet that senses the change in the electric field and tells the signal change the light.

  17. #17
    Ride Responsibly
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    Write your congress person and ask to allow bikes to treat stoplights and signs as yield signs, change the stupid laws.
    Until then wait thirty seconds then run the stupid light.

  18. #18
    Squeaky Wheel
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    Duplicate

  19. #19
    Squeaky Wheel
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    Quote Originally Posted by rodar y rodar
    I don`t think sensitivity is normally as big a problem as being in the exact right place.
    When properly adjusted, the exact right place does not seem to matter much. I can run over detector loops at 20MPH in a variety of spots and see the cross-street light change from green to yellow. The key is to ask your road department to adjust the sensitivity to detect bicycle wheels.

    Here are a couple of pages that talk about triggering lights in more detail:

    http://www.humantransport.org/bicycl...nals/green.htm
    http://www.humantransport.org/bicycl.../detection.htm

  20. #20
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    They often can't adjust the sensitivity with software or the electronic controllers, its the hardware of the loop itself. Not all systems are like this but ours are. Moving to camera sensors is the best way to go. That's what we're doing.

  21. #21
    weirdo
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    Here`s a good idea that`ll never happen. What if they put LED indicators under the green lamp that would show when the sensor (or not sensor) had been tripped? You pull up to the line and watch for the LED. If you don`t see it, move over or roll back a little or whatever until you know it`s registered your presense. Sounds cool to me for "perfect world" solution.
    Recalculating....

  22. #22
    ~Disc~Golf~
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    Quote Originally Posted by BrianMc
    Don't get carried away with the Gauss, or you might stick to Manhole covers and grates!

    How ignominious (how often do you get to use THAT word?) would that be?
    the magnet wouldn't be stationary
    Honestly... ahh I give up

  23. #23
    Moderator Moderator
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    I feel so left out - I don't believe we have any of those here in VT - or not on my commute anyways. When the light doesn't change it's just broken. In fact, one stayed red for a few days last year, until an accident occurred...then they fixed it.

  24. #24
    mtbr member
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    Quote Originally Posted by highdelll
    the magnet wouldn't be stationary
    If you are rolling the light before it cycles, why carry the magnet? Some can post until the signal changes the light, those who can't could circle, but most will put a foot down and the picture of someone's foot held....

  25. #25
    ~Disc~Golf~
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    Quote Originally Posted by BrianMc
    If you are rolling the light before it cycles, why carry the magnet? Some can post until the signal changes the light, those who can't could circle, but most will put a foot down and the picture of someone's foot held....
    who said I was rolling it?
    Honestly... ahh I give up

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