traffic lights and vehicle detection

Factual Questions
1

Every motorcyclist has occasionally been frustrated a red traffic light that refuses to turn green because the vehicle detection system, tuned to deal with 4000-pound cars, does not detect the presence of his 500-pound bike.

In addition to carefully running the light after being ignored for a couple of cycles, a number of suggestions have been offered, including:

-where to position your bike relative to the wire loop embedded in the pavement

-using one foot to lower your bike’s centerstand so that it’s closer to the loop

-installing a powerful magnet on the underside of the bike

Here’s the thing. The loop in the pavement is apparently serving as an inductor. Knowing this, I have some questions, and I hope we can get some electrical engineers to provide the straight dope on what might help, or couldn’t possibly help, to get bikes to trigger these lights.

[ul][li]A considerable portion of the metal in a motorcycle is aluminum. Not just the cylinder heads, but often the cylinder, engine block, and frame and suspension components. Contrast this with cars, in which the engine block, frame and body are often made of iron or steel. Am I correct in assuming that the presence or absence of aluminum (and other nonferrous metals) doesn’t affect the behavior of an inductive loop?[/li]
[li]Does a stationary magnet affect the behavior of an inductive loop? IOW, could the product at the above link possibly work, or is it snake oil? If it could theoretically work, should we expect a magnet of that size to compensate for the absence of several hundred pounds of steel?[/li]
[li]Where should the mass of a motorcycle be positioned so as to produce the greatest effect (signal) in the loop, in order to maximize the chance of being detected?[/li]
[*]Should we expect the lowering of the bike’s centerstand down to the pavement to make any noticeable difference? The stand typically only weighs a few pounds, but if it’s within a couple of inches of the pavement (as opposed to a couple of feet above the pavement, for the rest of the bike), could it have a much greater effect?[/ul]

2

This guy claims that magnets are the answer: Trigger Green Traffic Lights - YouTube

3

-where to position your bike relative to the wire loop embedded in the pavement

Yes, moving the bike may help the loop pick it up better.

-using one foot to lower your bike’s centerstand so that it’s closer to the loop

That can help, too.

-installing a powerful magnet on the underside of the bike

That helps, too.

**A considerable portion of the metal in a motorcycle is aluminum. **

The loop will detect aluminum.

Does a stationary magnet affect the behavior of an inductive loop?

It’s a hunk of metal, so sure.

Where should the mass of a motorcycle be positioned so as to produce the greatest effect (signal) in the loop, in order to maximize the chance of being detected?

I would say your best bet would be to get the engine over the center of the loop. That will put the most mass of the bike inside the loop.

Should we expect the lowering of the bike’s centerstand down to the pavement to make any noticeable difference?

It might. That puts a hunk of metal closer to the loop, which is more likely to trigger it.

I played around with a traffic detector many years ago. I used one as part of a control system for a silo as one of several methods that the system used to confirm that a truck was under the silo’s chute. The one I used could be adjusted so that it was so sensitive that it would pick up the metal in my steel toed boots.

They usually set them so that they won’t trigger on a bicycle but should trigger on a motorcycle. However, sometimes they don’t get it adjusted quite right or things get old and out of tune and a motorcycle won’t trigger it any more. If you find one that won’t trigger on your bike, call up the local traffic engineer or whoever is in charge of traffic lights and such in your area and tell them that they need to adjust it.

4

Why would they do that? I’ve had to trigger lights from my bicycle and they mostly seem to work if you are positioned correctly.

5

I always get off my bike and go push the pedestrian walk button. (Then run back to my bike.)

6

The good news is that around here they are no longer putting in loops and are instead using the camera type detectors on the poles. Which makes sense, you don’t have to dig up the street if something goes wrong. 90% of the time when a call comes in about a light malfunctioning it is because someone stopped 3 car lengths back from the stop line and the mechanism can’t detect them.

7

This is an old .pdf article from that trusted publication, Motorcycle Consumer News

http://www.mcnews.com/mcn/features/loopMay07.pdf

I didn’t re-read it this time, but thought it was good info when it was new.

I don’t know what really works best. Personally, I’ve never been able to have consistent, reproducible results from any specific technique. However, my method is to “serpentine” along the left-most sensor wire and come to a stop inside the loop at approx the 11 o’clock position (for whatever that’s worth).

8

Okay, what if you’re riding a horse? :smiley:

In fact, in the vicinity of Griffith Park (Los Angeles), where there is a large horse stables, there are pedestrian walk buttons that are positioned higher up from the ground, the better for horse riders to reach.

Photo (although I have no idea where this is located).

9

You think motorcycles have it bad, try tripping a light on a carbon fiber bicycle! Even steel, titanium, and aluminum bicycles usually don’t have enough metal to trip the crossing light.
Here’s what I do.

  1. As others said, push the crosswalk button if there is one.

  2. Make a right on red and do a U-turn later on.

  3. In some states it’s legal for cyclists to cross at a red light after waiting a period of time and ensuring that it can be done safely.

  4. In states where it’s not legal, cross anyway.

10

Some states have passed laws that allow a cycle to proceed through the light after a certain amount of time (45-60 seconds) has passed which I think is fair.

Where I get tripped up on these things is on freeway entrance ramps. Many times they are 2 lanes so trying to blow the light can get you clipped by a car going through his green light next to you. Gotta be extra careful on them ramps.