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Old November 9th, 2011, 05:45 AM
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GeckoGeek GeckoGeek is offline
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Join Date: May 2004
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Default Re: MORE on magnetic diversions.

Quote:
Originally Posted by Kaonohi View Post
Traffic light car detection technology is visible in the roadway - I thought it was based on the old pressure-switch technology.
Frequently you can see the slots they cut to put the wire loops in place. So they're sometimes visible. I know it's a common belief that it's "pressure" or "weight" but it's not. It works more like a metal detector. The metal in the car will detune the frequency of the loop.

Sometimes you'll see a pressure-switch system. It's those rubber hoses that run across the road. (Or if you're old enough to remember service stations where your heard a "ding-ding" when you drove up.)


Quote:
Originally Posted by Kaonohi View Post
I don't know why they are different, nor why they are only on one side of the tunnels.
If the purpose is just to count the cars to give a over-all traffic pattern they only need to be on one side. For every car that travels on the windward side there will be (or was) one car traveling on the leeward side. (Unless there's a secret off ramp the public doesn't know about.)

You need both sides only if you're trying to get real-time data on the traffic heading toward the tunnels.
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