In the left hand turn lanes that have an arrow, how do they know there is a car waiting to make the turn? I assume it has something to do with the metal lines i see in the lane, but how does the car trigger it?
The metal lines cover an electromagnetic coil through which a certain electric current is flowing, creating a magnetic field. If a car is standing on the lines, the car’s metal generates a magnetic field caused by the coil’s field, and this again induces changes in the original coil current. The sensor thus knows when a car is standing in the lane and can control the lights adequately.
Too bad if your car is made out of fibreglass, and the engine is cast from non-ferrous metal - you could be stuck in the turning lane forever…
Or on a motorcycle - this is a well-known problem among bike riders. I have had to just run the red light (at an empty intersection) instead of being stuck there my entire life.
In my area we have a left turn lane, in which too many people don’t pull up to the stop line, and consequently they don’t trigger the turn arrow. Hence, you can wait up to 5-10 minutes for the light to finally cycle or the idiot to run the light (ironically triggering the sensor, which is normally on a 20-25 second cycle). Since honking at these oblivious morons is useless, sometimes I have to drive around them and trigger the light myself (stopping over the stop line), which is kinda dangerous and probably illegal.
Anyone else have a better solution to this problem?
I thought there were pressure sensors at the heads of the intersections… oh well.
definitely true about the motorcycles. I would try to stop right on top of a line, and then rock left and right to influence the magnetic field. It even worked sometimes. But way back when I had that Honda 50cc scooter, gooooood luck. I ran them all the time late at night.
It helps to have a passenger. MrsB is designated “get off and hit the pedestrian button” pusher.
Sometimes it helps to flash your headlights. I think it activates the same sensor that detects the stobe light on an ambulance. I think some intersections have a sensor that picks up the sound of a siren. I’ve seen the Highway Patrol change the light with a short burst on the siren.
If the cycle goes more than twice I figure they’re idiot. I usually get out of my car, tap on their window (which is usually good for a cardiac inducing moment on their part, as I am a BIG man) and tell them they need to move forward to trigger the light. I then calmly stroll back to my car and buckle up before the light changes back.
Thanks Schnitte, Answered my question really quick… Too bad I haven’t been around the past couple days to see it. 
So its all done with magnets. Tell you the truth, when I was trying to figure it out, I never once thought it might be magnets.