Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site utastro.UUCP Path: utzoo!watmath!clyde!bonnie!akgua!whuxlm!whuxl!houxm!mtuxo!mtunh!mtung!mtunf!ariel!vax135!timeinc!phri!pesnta!amd!amdcad!amdimage!prls!philabs!cmcl2!seismo!ut-sally!utastro!bill From: bill@utastro.UUCP (William H. Jefferys) Newsgroups: net.bicycle Subject: Re: left turns Message-ID: <292@utastro.UUCP> Date: Fri, 28-Jun-85 13:04:59 EDT Article-I.D.: utastro.292 Posted: Fri Jun 28 13:04:59 1985 Date-Received: Wed, 3-Jul-85 06:17:39 EDT References: <605@intelca.UUCP> <1636@reed.UUCP> <328@varian.UUCP> <2@uw-june> Organization: U. Texas, Astronomy, Austin, TX Lines: 35 > > > >1) most left turns around here have sensors in the street, so they don't > > > change unless something large and metalic is sitting on them. > > > > It angers me however that the state can declare a bicycle a vehicle > > and then interfere with its safe and efficient operation with these > > ridiculous sensors. My motorcyclist friends have the same problem, > > incidentally. Does anyone know if these sensors have adjustable > > sensitivity? They are based on a metal object interfering with a > > magnetic field, so I should think so. > > > 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. > Actually, there is a way around this, but it has to be done when the sensor loop is *installed*. (Described in John Forester's *Cycling Traffic Engineering*): If the loop is installed as a figure 8 instead of (as is normal) a plain loop, it will simultaneously become more sensitive to low-mass objects such as bicycles over it, and less sensitive to large objects, such as trucks, in the adjacent lane. Unfortunately, very few of the people responsible for installing these things are aware of this. It is really up to bicyclists to organize and make waves at city hall! -- "Men never do evil so cheerfully and so completely as when they do so from religious conviction." -- Blaise Pascal Bill Jefferys 8-% Astronomy Dept, University of Texas, Austin TX 78712 (USnail) {allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp) bill%utastro.UTEXAS@ut-sally.ARPA (ARPANET)