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Wednesday June 25, 2008

Signal Loops

We've been packing up stuff for our move at work this week. As part of that I've been going through trade magazines and catching up before throwing them out. One kind of interesting article concerned research into traffic detection loops in roads. As someone who rode scooters for years, I can attest that traffic signals that use detection loops can be very frustrating because the motorcycle doesn't always have enough iron in it to trigger the loop that sits in grooves cut in the pavement (even worse for bicycles). Therefore you get stuck at a red light that won't change until someone else drives up behind you (or you run the red light under the "malfunctioning traffic light" justification).

This article talked about changing the sensitivity of the loops, but it also pointed out that the best chance you have of being detected is to be right on top of the wire, whereas I guess I believed you should be in the center of the loop itself. Being in the center is actually one of the worst spots because it puts you the maximum distance from both sides of the wire loop.

Some signals use some kind of radar on the signal head itself that is pointed at the lane and therefore "sees" traffic waiting. The advantage there is that when you repave (every 5-10 years) you don't have to reinstall loops that typically get torn up or buried in a paving opeartion. I think those would be better at detecting motorcycles and bicycles too.

. . . and into the recycling bin it goes!


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