Traffic Light Spoofer for Cyclists

(posted only to sci.electronics.basics, follow-ups set too)

It requires a lot of optical power along a particular angle, frequency needs to be nail-on (fractions of Hz), and in most places cities and counties (parishes, too) and states have made in some part of their legal code made it against the rules of the road and, if caught, you might face some fines or worse. A 9V battery is unlikely to handle the power required to get enough of the right wavelengths into the right angle of acceptance, anyway.

Jon

Optical? Is the OP in the USA because I think that they're all inductive loops in the ground, here in the States.

For motorcycles, there are devices sold that are just large magnets that attach to the bottom of the frame. I haven't tried them, but if I run into a sensor that doesn't pick me up then I call the local traffic division and they're very cooperative. They just turn the sensitivity up to 11.

Bob

Do you mean that your bike is ignored by magnetic-loop sensors?

I'd think that a reasonable bit of electronics and a ferrite-core loop antenna could detect the big loop frequency and generate some signal that would simulate a car. It would take a little research, but the numbers don't look unreasonable to me; the loops are just metal detectors, looking for a fairly small inductance change.

John

But might be unnecessary if you have some cooperation from the local DoT. I've found that just laying the bike down a little over the sensor area of the road gets almost all the lights to trigger in our area (northern Cal.) and the traffic authorities are pretty good about coming out and adjusting the few that don't. This assumes you have aluminum rims to trigger the induction loop detectors.

Perhaps _I_ may have misunderstood.

What I was thinking about was the emergency vehicle access to the light system, which can be used to force a change. The OP (whom we all know) wrote "spoofer that would trick the intersection into changing the light" and interpreted that as the devices used by emergency vehicles.

I read the OP one way, you another. Now we just need to hear from the OP about it.

Jon

I have found that just putting the front wheel on the cut line where the sensor loop is installed is enough.

unfortunately motor cycles have thicker tyres smaller wheels and are harder lie down and pick up.

OTOH Bret says 9v (not 6V or 12V) so chances are he's using leg-power and not a motor.

Ahhhh. After doing a little research, I see that there is an infrared system that allows emergency vehicles to preempt the traffic light state.

This system is for emergency vehicles and not for bicycles. I can only hope that if this (or any) bicyclist decides to use such a "spoofer" that he/she gets run over by a large car. This will help with the too-many-sociopaths-alive problem.

Bob

See .

See also .

OTOH I could har simply tead the subject line! "cyclists" generallt excludes motorcyclists. D'oh.

I once saw a web page, which I can't find now, where the cyclist tipped the bike, to make the frame more nearly parallel to the loop, to improve the inductive coupling.

A google search just now turned up mostly neodymium magnets.

If you're talking about that strobe that emergency vehicles use, be sure you don't get caught.

Have Fun! Rich

The article says, "Did the vendor not stop to think about the potential for abuse? Did they think that nobody would ever figure out how to abuse the system?" But the designers designed these some time ago and did quite a bit already to flummox would-be abusers. (What some manufacturers failed to do was avoid publishing their schematics, though -- so people did get access to the details, if they bothered to look.) There is a narrow band optical filter which allows certain wavelengths in; there is an acceptance angle which limits the angle at which the light is accepted; there is a precise frequency (think small numbers of milliHertz narrow-band set somewhere between 10 and 20 Hertz reprate) allowed by the electronics. One needs to know the precise frequencies (I know of two of them), how to pump out enough IR in the right band in a way that folks around you don't notice (not so easy without flash-lamps, which make things pretty obvious if you use them but which are fine with emergency vehicles), etc. I think other means, too, were also considered and were disposed of based on the application requirements at the time.

Part of the problem is that times change (high power IR LEDs, for example, with narrower dispersion angles and fancy microcontrollers that are cheap, accurate, and everywhere) and their documentation did get lose into the public view so that the labor attempting to find the right Hz was eliminated for some.

Yeah, that was an expected response, I suppose, that I wasn't aware of.

Jon

I have always wondered why they did not design the strobe so that it turned lights red in all directions. Then all traffic would stop, except for the emergency vehicle, and the worst that an illegal strobe could do would be to disrupt traffic and annoy people.

Paul

ed

No, the worst situation under that system is that the legal strobe on the emergency vehicle fails to trigger the signal. Then the emergency vehicle goes barreling through the red and right into the cross traffic that still has a green. Better to have things so that even if parts fail they tend to do so in ways that are still fairly safe.

No, the worst situation under that system is that the legal strobe on the emergency vehicle fails to trigger the signal. Then the emergency vehicle goes barreling through the red and right into the cross traffic that still has a green. Better to have things so that even if parts fail they tend to do so in ways that are still fairly safe.

Most traffic lights are set to fail-safe as flashing red, which at least requires all vehicles to stop before proceeding. Emergency vehicles should never just barrel through an intersection with the assumption that the lights are properly set, and it should be easy enough to verify that the lights in the cross direction are indeed also red. One fail-safe indicator would be to make the lights flash when the emergency condition is set. Otherwise there could be indicators on the sides of traffic lights to indicate their color.

Paul

The sensor picks up the strobe, the strobe doesn't do anything by itself. The controller can be programmed to do whatever the traffic engineer wants, including "all-red" which would at least eliminate the incentive to have an illegal strobe.

It's highly unlikely that they would ever catch you with an illegal strobe, unless its use caused an accident.

With the sensor loops here in Vancouver BC, positioning over them is important to getting some of them them to trip. We've got 4 kinds of loops, or rather, pavement cuts over the loops -- circular, diamond, rectangular, and double-rectangles. With the former three, positioning one's self & bike over the right half and maybe leaning your bike a little gets them to trip. With the latter (double-rectangle) type, just position yourself over the backbone/ centre cut.

If that doesn't work, you can share the left turn lane and invite the driver behind you to come up and stop their car over the sensor. The drivers are grateful & appreciative that you're not holding them back, and everybody (including you) gets to go. If there's no driver behind you and the sensor doesn't trip the traffic light, just treat the intersection as a 4-way after waiting out what should have been one normal light cycle. Or just go, if there's nobody around to be adversely affected by your traffic movements, and no traffic cops lurking behind a nearby billboard or something, just itching to issue a ticket to somebody.

cheers, Tom

ed

he

be

ncy

if

Still strikes me that the current system where the emergency vehicle driver sees a clear green traffic light is safer than one where he has to check for secondary indicators for the cross traffic direction. And flashing red for cross traffic is not as safe since drivers in that direction may well see that other traffic is stopping and start to cross after a momentary stop without noticing the emergency vehicle maneuvering past the stopped vehicles. It's also better for the emergency driver if the vehicles in front of him have a green so they can maneuver out of his way.

If illegal strobes ever become a significant problem it seems to me that can be remedied by stiff penalties combined with cameras to record the plate number of any vehicle that sends out a strobe signal. But don't decrease the safety of the current system for letting emergency vehicles have a green signal while the other directions have a solid red.

Bretski, Back when I used to ride on the road I used to get stuck at a certain intersection...I found the following on Instructables.com, I never got around to trying it:

ABS-ski

If your bicycle will not trigger a green light, the signal can be considered defective, and you have the legal right (in the US) to proceed as long as you yield to cross traffic.