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From: powers@noscvax.UUCP (William J. Powers)
Newsgroups: net.bicycle
Subject: Re: left turns
Message-ID: <998@noscvax.UUCP>
Date: Thu, 4-Jul-85 15:40:25 EDT
Article-I.D.: noscvax.998
Posted: Thu Jul  4 15:40:25 1985
Date-Received: Sun, 7-Jul-85 05:50:29 EDT
References: <605@intelca.UUCP> <1636@reed.UUCP> <328@varian.UUCP> <2@uw-june> <331@varian.UUCP>
Organization: Naval Ocean Systems Center, San Diego
Lines: 29

> > In fact, these sensors are adjustable, but if the sensitivity is made
> > too high, a really massive piece of metal (like a truck)
> > can activate the one in the adjacent lane.  This can cause problems
> > like a left-turn signal going on when no one is waiting to make a left
> > turn!  So you see, it's not quite as simple as it seems at first.
> > 
> 	Obviously, any device of this type can be misadjusted.  My point
> 	is that if the device cannot be adjusted to accomadate the opera-
> 	tion of all vehicles-- trucks, cars, motorcycles and bicycles--
> 	that legally use the road then the device is inadequate and a
> 	more reasonable system should be adopted.  Also, I can't quite
> 	believe that the sensitivity required to sense a bicycle directly
> 	over the loop is even close to that required to sense a truck in
> 	the adjacent lane.  Even if it is, to occasionally set off a left
> 	turn arrow when no one is there seems more desirable than not
> 	setting it off at all for motorcycles and bicycles.
> 

I know that in Los Angeles they have evidently solved this problem.
I don't know how.  Maybe some of you LAans know or can find out.
Here in San Diego we have initiated a study to solve this problem.
Another suggestion that might work is to add an inductor or some such
resonant circuit to a bicycle that would increase its sensitivity.
I do not, however, have sufficient information on the workings of
these loop detectors to attempt to design such a system.  If something
as simple as this could be made to work the bicycling community would
be greatly indebted ( not to mention the profits that might be
involved ).
Bill Powers