My neighbor owns a motorcycle and sometimes has to sit through several rounds of lights at the intersection near our house because the traffic light sensor embedded in the asphalt doesn’t pick up enough steel to let the traffic light computer know someone is waiting at the intersection.
What? You didn’t know that’s how a lot of lights work these days? Yep, other than during rush hour (when they’re usually on simple timers like they were in the old days), many traffic lights, especially those with the arrows that allow you to turn left, work off some kind of sensor. The most common is the inductive loop under the road.
When you’re in a car (which has a lot of steel in it), idling right behind the crosswalk, the car acts like the core of an inductor, causing the loops of wire under the asphalt to trigger the computerized traffic light box at the intersection. Basically, your car is telling the light, “Hey, I’m here, let me through.”
But my neighbor’s motorcycle doesn’t have enough umph, and he’ll often get shut out of an entire sequence of red-green. Even the cars coming in the opposite direction get the green, but he sees only red.
Bicyclists have the same problem. True story: I was once on a bike in Irvine, California (don’t ask) and made a left turn without the arrow (because it wasn’t turning green!) and got pulled over by a police car for running the red. Luckily, he let me go with a warning, but it really wasn’t my fault. If motorcycles don’t have enough steel in them to trigger the sensors, how could bicycles? (Actually, I’ve recently found a couple patents for devices that would hook up to bike’s for just the reason. Check this one out.)
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As a long time biker, there is an easier solution. It is called a Green light trigger. It is simply a rare earth supermagnet, usually encased in plastic. You mount it by wire ties or similar to the frame on the bottom of the bike. I have them 3 HDs and they work fine.
posted by David on 11-5-2008 at 7:50 am
in NC, they have actually made it legal for motorcyclist to turn on red when this occurs…
posted by theYerg on 11-5-2008 at 8:04 am
I’m a bicycle commuter and worked late last week. The gates were closed when I left and of course wouldn’t open. It would be nice if they would just have a button to open the gates to let us non ferrous people out
posted by Tim C on 11-5-2008 at 8:38 am
I was going to post what theYerg did – here in NC motorcyclists can turn on red being that 1) its ‘all clear’ (obviously) and 2) they’ve sat through at least 1 light cycle. Not a bad law in my opinion…
posted by Elphaba on 11-5-2008 at 9:28 am
As a motorcyclist myself, I’ve suffered through this problem at stoplights with sensors in the road. I read that one way to trigger the sensor is to put the bike’s sidestand down as you pass over the wire in the road. That gets enough metal in proximity to the sensor to trigger it. The probelm with that as bikers know is that you then have to get the sidestand back up before you proceed or your bike will stall when you release the clutch (there is a cutoff to keep you from driving with the sidestand down). I haven’t tried it becuase I just don’t like the idea of being underway or in gear (even with the clutch in) with the sidestand down.
recaptcha: elation ideal (like riding!!)
posted by Annette on 11-5-2008 at 9:40 am
I’ve heard you don’t even need a special device to attach to your bike or moped or motocycle to make the sensors feel you. Just attach a couple powerful magnets to the bottom of your frame should do the trick. Like the ones that a the size of hockey puck.
127th Villeneuve
posted by Lou on 11-5-2008 at 9:49 am
There’s also a passive solution for triggering without adding a bunch of stuff on your ride. Several places sell strong permanent magnets for this purpose that aren’t bigger than a square-inch. You mount it to the lowest point of your frame and the added magnetic field helps trigger the inductance coil, making you seem “larger” than you really are (kind of like reverse-stealth). I’ve rarely had problems using the magnet, but I installed it when I first got the bike so there’s not a “before” reference to say how much it improves activation.
posted by John on 11-5-2008 at 10:36 am
I ride my bicycle in a pretty urban area, and when this happens I either ask someone walking by on the sidewalk to hit the crossing button for me, or if no one’s around, I get up on the sidewalk to do it. Not really the most convenient way to do it…
posted by gibson8or on 11-5-2008 at 11:11 am
In California it is legal for any vehicle to run a “malfunctioning” light system. You must be left out of one complete cycle of the system and it is then considered to be “malfunctioning” and you may proceed with caution through the light.
posted by Taylor on 11-5-2008 at 11:41 am
“I made a left turn without the arrow (because it wasn’t turning green!) and got pulled over by a police car for running the red. Luckily, he let me go with a warning, but it really wasn’t my fault.”
So, you are saying that there weren’t any alternatives? Dismount and walk to the crosswalk, switch to the right lane, etc.
All I am saying is that turning left against a red is a willful action and you had a choice. Claiming that it wasn’t your fault is silly.
:)
posted by Mark on 11-5-2008 at 11:58 am
I went to college in Irvine and rode my bike all the time as I had no car. I had a few problems with the police for riding my bike through the crosswalk, rather than walking it.
Now, as a motorcyclist, I have problems with the lights changing and I can’t exactly use the crosswalk. I’ve got a magnet on my bike, but it really doesn’t work. I think the reason it would work with the Harleys is because they’re lower to the ground. My BMW has a lot of ground clearance so the magnet is further away from the sensors. I sometimes end up making a bunch of right turns and using residential back streets to get where I’m going simply because I have no way to get around the lights. It’s usually only a problem late at night, though, when there are fewer people on the road in my area.
posted by Tomas on 11-5-2008 at 12:33 pm
Actually, you don’t need the contraption, you just need some really strong magnets. Strong magnets make your vehicle seem heavier to the sensors.
posted by Karleigh on 11-5-2008 at 5:25 pm
Hey! What’s wrong with Irvine? ;)
UCI is my alma mater as well, but I agree that police here are really, really anal. My f-i-l got pulled over for driving 2 miles above the speed limit.
Interesting article, I learned something new! I always thought those circles worked off of weight, so thanks for clarifying that for me =).
posted by CK on 11-5-2008 at 6:10 pm
I pedal to work at night. The light on my corner does this as well. At night I simply stop, look, and go. During the day I have to wait for a car coming from either direction. sometimes a car turning will cross at the right spot to trigger it. This is a small price to pay for not buying gas.
posted by gus on 11-5-2008 at 10:16 pm
Whether or not these sensors can detect motorcycles and bikes is determined by the sensor itself. For example, in nearby Boulder, CO (which has a lot of bicyclists) there are turn light sensors that can detect bicycles. They have a painted bicycle sign showing where the cyclist should position his/her bicycle. And as a motorcycle rider, I found that these also detected my motorcycle.
posted by Chad Cloman on 11-6-2008 at 9:47 am