Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site masscomp.UUCP
Path: utzoo!watmath!clyde!bonnie!masscomp!hank
From: hank@masscomp.UUCP (Hank Cohen)
Newsgroups: net.analog,net.auto
Subject: Re: Car Detectors
Message-ID: <986@masscomp.UUCP>
Date: Tue, 6-May-86 18:03:32 EDT
Article-I.D.: masscomp.986
Posted: Tue May  6 18:03:32 1986
Date-Received: Wed, 7-May-86 04:13:49 EDT
References: <2974@watvlsi.UUCP> <4839@topaz.RUTGERS.EDU> <992@kitty.UUCP> <4347@srcsip.UUCP>
Reply-To: hank@masscomp.UUCP (Hank Cohen)
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Xref: watmath net.analog:805 net.auto:10351
Summary: Speed detection

In article <4347@srcsip.UUCP> williams@srcsip.UUCP (Susan Williams) writes:
>When I see these things, I am always intrigued about how they are
>installed.  There is usually a thin octagonal shaped cut in the
>pavement, and none of the surrounding pavement seems to have been
>disturbed or replaced.  Does anyone know how they do this?  So
>far I have guessed that they must not be placed very deep.

They are installed by cutting narrow slots in the pavement with a diamond saw.
The detector cable is then dropped into the slot and it is refilled with asphalt.
That is why the slots are octagonal the cable doesn't like to turn
sharp corners.

I have another question.  I have often seen these detectors placed 
across the freeway two per lane and I wonder if they are being used
just to count traffic or does having two separated by a known distance
allow them to also measure speed.  This could be a means of monitoring
55 mph speed limit compliance.
	Iligitime non Carborundum
		Hank Cohen