youngqd@jacobs.cs.orst.edu (Dean Youngquist) (04/12/91)
The fire trucks in my town seem to trip traffic lights to green in their direction as they are approaching the intersection. Does anyone know how they do this? I thought they might have a system using infra-red light ? If it is infra-red how can they work in the day-time? Doesn't the sun put out infra-red that would interfere ? Dean Youngquist youngqd@jacobs.cs.orst.edu Corvallis, Oregon 97330 Tel. (503) 757-0335
fval_ltd@uhura.cc.rochester.edu (Trey Valenta) (04/12/91)
In <1991Apr11.211957.7309@lynx.CS.ORST.EDU> youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: >The fire trucks in my town seem to trip traffic lights to green in >their direction as they are approaching the intersection. Does anyone >know how they do this? I thought they might have a system using >infra-red light ? If it is infra-red how can they work in the day-time? >Doesn't the sun put out infra-red that would interfere ? I don't know about how the lights are changed, (I'd think radio) but as for the sun's inteference, what one can do is put a filter that allows only IR to pass through, and the light from a transmitter is many times more powerful that what's put out by the sun. trey valenta fval_ltd@uhura.cc.rochester.edu
bc338569@longs.LANCE.ColoState.Edu (Brian Catlin) (04/12/91)
In article <1991Apr11.211957.7309@lynx.CS.ORST.EDU> youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: >The fire trucks in my town seem to trip traffic lights to green in >their direction as they are approaching the intersection. Does anyone >know how they do this? Here they use radar detectors mounted on the wire or pole that the stoplights are on. There are two sets per intersection. One points North and South while the other one points East and West. Fire trucks and police can both trip these but the computer sometimes screws up and turns all four directions green! This can be quite confusing :-) If you see radar guns mounted on the fire trucks then that's how they probably do it. Police just have to point their guns up so that there is a straight path to the detectors when they want to change the lights quickly. This is done very infrequently since it confuses the computers so much. Hope this helps! B. J. Catlin bc338569@longs.lance.colostate.edu
moroney@ramblr.enet.dec.com (04/12/91)
In article <1991Apr11.211957.7309@lynx.CS.ORST.EDU>, youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes... >The fire trucks in my town seem to trip traffic lights to green in >their direction as they are approaching the intersection. Does anyone >know how they do this? I thought they might have a system using >infra-red light ? If it is infra-red how can they work in the day-time? >Doesn't the sun put out infra-red that would interfere ? Some systems have a photoelectric sensor aimed at the traffic lanes and a phase locked loop circuit that is synchronized to the flashing emergency lights on the emergency vehicles. When the PLL detects the flashing lights in a certain direction, it turns the light green in that direction. Other lights may use radio triggers, or (especially those right near fire/police stations) controlled right from the station. -Mike
sony@buhub.bradley.edu (David Lennie) (04/12/91)
In <1991Apr12.042157.6685@engage.enet.dec.com> moroney@ramblr.enet.dec.com writes: >Some systems have a photoelectric sensor aimed at the traffic lanes and a phase >locked loop circuit that is synchronized to the flashing emergency lights on >the emergency vehicles. When the PLL detects the flashing lights in a certain >direction, it turns the light green in that direction. Wouldn't this also detect the flashing lights on construction vehicles or tow trucks? Does the sensor simply pick up the presence of any flashing light or does it confirm that it is actually a police or fire vehicle by measuring frequency of flashes or something similar? If it does measure the frequency, wouldn't it be susceptible to error due to slight variances in the flash frequency caused by low or high battery voltage in the vehicle? I am intrigued (obviously). Explain furthur.
brian@ucsd.Edu (Brian Kantor) (04/12/91)
The "Opticon" sensors in use throughout San Diego County for traffic light control by emergency vehicles use a photocell in a focusing assembly that's pointed down the road. They ignore changes in ambient light levels and look for flash rates of either 10 or 16 hz, which the bus or emergency vehicle generates with a very bright xenon strobelight. The two different rates are used for different purposes - one is for emergency vehicles and causes the lights to go green in that direction and red in all others. The other flash rate is designed for use by transit buses and simply extends the green cycle so that the bus won't have to stop suddenly if the light changes. To my knowledge, the second isn't actually being used around here. - Brian
tomb@hplsla.HP.COM (Tom Bruhns) (04/12/91)
youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: >The fire trucks in my town seem to trip traffic lights to green in >their direction as they are approaching the intersection. Does anyone >know how they do this? I thought they might have a system using >infra-red light ? If it is infra-red how can they work in the day-time? >Doesn't the sun put out infra-red that would interfere ? Systems I've seen used pulsed light; it's easy to look for the AC component at a particular frequency. It's also pretty easy to filter the receiver so it's looking at the wavelength of peak emission of the transmitter. The receivers tend to be pretty directional, too: aren't they in pipes perhaps 1" diameter and 6" long? I was always annoyed that empty, "out of service" busses in Santa Clara county would trip the light and hold up long lines of left-turning cars for another cycle of the lights. Busses there used them more than emergency vehicles!
johne@hp-vcd.HP.COM (John Eaton) (04/12/91)
<< < The fire trucks in my town seem to trip traffic lights to green in < their direction as they are approaching the intersection. Does anyone < know how they do this? I thought they might have a system using < Dean Youngquist youngqd@jacobs.cs.orst.edu < Corvallis, Oregon 97330 Tel. (503) 757-0335 ---------- If you examine the stop lights you will see a small "probe" that points towards oncoming traffic. This probe detect the emergency lights and switches the light green in that direction. The key light is not the normal red flashers but rather a single Xenon strobe light that all emergency vechicles in the town have mounted in front. (And you thought that was there to get YOUR attention?). I figured this out one day when I was waiting for a left turn signal (On ninth street in Corvallis), when an ambulance approached the light with ONLY the strobe light flashing. The light gave that direction immediate clearance. I suspect that it keys in on a certain rep rate for a flashing light. John Eaton !hp-vcd!johne
lrk@k5qwb.lonestar.org (Lyn R. Kennedy) (04/13/91)
youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: > The fire trucks in my town seem to trip traffic lights to green in > their direction as they are approaching the intersection. Does anyone > know how they do this? I thought they might have a system using > infra-red light ? If it is infra-red how can they work in the day-time? > Doesn't the sun put out infra-red that would interfere ? > > Dean Youngquist youngqd@jacobs.cs.orst.edu > Corvallis, Oregon 97330 Tel. (503) 757-0335 One system that works uses a strobe light on the vehicle. This can be easily seen among the other lights. The traffic signal also has a detector up near the middle of the intersection for each direction. I've heard Dallas is experimenting with a system that uses radio in the 800 Mhz range but it's small scale and on the other side of town so I haven't had much time to check it out. ------------------------------------------------------------------------- lrk@k5qwb.lonestar.org lrk@k5qwb.UUCP 73, utacfd.utarl.edu!letni!rwsys!kf5iw!k5qwb!lrk Lyn Kennedy K5QWB @ N5LDD.#NTX.TX.US.NA P.O. Box 5133, Ovilla, TX, USA 75154 -------- "We have met the enemy and they are us." Pogo -----------------
wcollin@relay.nswc.navy.mil (William Dave Collins - E41) (04/13/91)
Same thing I was told by a firefighter in Fredericksburg, Va. The only one is located about a block away from a new station. It is on one of the busiest highways in the town. The FF stated that it responded to the rep rate of the strobe. In fact he said that one day during check out of the equipment he noticed every car stopped at the intersection a block away! He then realized he had the strobe running!! It would be nice if the city would put up more of these, especially on the main routes to the hospital so that us volunteer ambulance squads can navigate easier. David ============================================================================== Wm David Collins BSEE, EMT-Cardiac, ACLS, expired KA4ZHQ Naval Surface Warfare Center Code E-41, Networks Branch Dahlgren, VA 22448 W(703) 663-7744, H(703) 775-3292 DDN mail: wcollin@relay.nswc.navy.mil ==============================================================================
moroney@ramblr.enet.dec.com (04/13/91)
In article <1991Apr12.063837.7120@bradley.bradley.edu>, sony@buhub.bradley.edu (David Lennie) writes... >In <1991Apr12.042157.6685@engage.enet.dec.com> moroney@ramblr.enet.dec.com writes: > >>Some systems have a photoelectric sensor aimed at the traffic lanes and a phase >>locked loop circuit that is synchronized to the flashing emergency lights on >>the emergency vehicles. When the PLL detects the flashing lights in a certain >>direction, it turns the light green in that direction. > >Wouldn't this also detect the flashing lights on construction vehicles >or tow trucks? > >Does the sensor simply pick up the presence of any flashing light or >does it confirm that it is actually a police or fire vehicle by >measuring frequency of flashes or something similar? If it does >measure the frequency, wouldn't it be susceptible to error due to >slight variances in the flash frequency caused by low or high battery >voltage in the vehicle? > >I am intrigued (obviously). Explain furthur. Most police and firetrucks nowadays have electronic flashers instead of the old style light-with-rotating-mirror they had several years ago. The tow trucks, etc. still use the old style (cheaper). The newer flashers are timed electronically, often with a somewhat complex pattern, and the timing isn't dependent on the battery voltage (as long as it's strong enough to run the apparatus) The timing on the sensor must be coordinated with the timing of the emergency lights, so random tow trucks don't set them off while the police cars/firetrucks do. Even if the tow trucks occasionally trip it, no bug deal (as long as the driver doesn't learn this and start abusing this knowledge) -Mike
jeh@dcs.simpact.com (04/13/91)
In article <1991Apr11.211957.7309@lynx.CS.ORST.EDU>, youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: > The fire trucks in my town seem to trip traffic lights to green in > their direction as they are approaching the intersection. Does anyone > know how they do this? I thought they might have a system using > infra-red light ? If it is infra-red how can they work in the day-time? > Doesn't the sun put out infra-red that would interfere ? Around here the system (called, I think, "Opticom", one of the less-inventive names I've heard lately) uses visible light. A large strobe light atop the fire truck (or paramedic vehicle), running at a fast, but visible, flicker rate, does the job. Yes, the sun and lots of other things put out visible light also, but (a) the pickup unit is not just a CdS cell open to the air; it includes a telescope-like arrangement of lenses (it actually looks like a little telescope, attached to one of the regular R-Y-G traffic light assemblies) so that the pickup area is fairly limited, and (b) not very many things (certainly not the sun) put out anything that looks like a strobe at 10 or 15 (or whatever) pps. It is amazing how well a signal can be picked out of noise, provided you know the exact characteristics of the signal in question. In this case, a simple DC blocking cap will get rid of most of the ambient light, and then it's pretty easy to filter for a steep-sided narrow pulse waveform at whatever the right freq is. At night the pickup will "see" 60 Hz hum from the street lighting, but that's easy to filter out too. Consider how bad static from a poorly-wired car can be in an AM radio, and you'll have some idea how easy it is to "see" a strobe light, even against a brighter background. Since spike waveforms have harmonics that (theoretically) go all the way up the spectrum, they might be able to get away with looking for one, or just a few, of the higher-order harmonics. The first units installed here (15 years ago or so) had PAR floodlamps attached, pointing down the street in each direction from which the intersection could be controlled. Once the strobe had command of the intersection, the appropriate lamp would be turned on to let the driver know that the intersection was indeed controlled and that the green light wouldn't suddenly turn yellow. Later units lack this; apparently the system works so well that they don't need this confirmation. Next time you see a fire truck go by, look at the array of flashing lights and see if there isn't a big (8" diameter reflector or so) strobe among them. --- Jamie Hanrahan (x1116), Simpact Associates, San Diego CA Chair, VMS Internals Working Group, U.S. DECUS VAX Systems SIG Internet: jeh@dcs.simpact.com, or if that fails, jeh@crash.cts.com Uucp: ...{crash,scubed,decwrl}!simpact!jeh
ckinsman@yoda.eecs.wsu.edu (Chris Kinsman) (04/13/91)
In article <1991Apr11.211957.7309@lynx.CS.ORST.EDU> youngqd@jacobs.cs.orst.edu (Dean Youngquist) writes: >The fire trucks in my town seem to trip traffic lights to green in >their direction as they are approaching the intersection. Does anyone >know how they do this? I thought they might have a system using >infra-red light ? If it is infra-red how can they work in the day-time? >Doesn't the sun put out infra-red that would interfere ? > >Dean Youngquist youngqd@jacobs.cs.orst.edu >Corvallis, Oregon 97330 Tel. (503) 757-0335 I have been on departments in the past that use a system like that. The most common is one called Opticom. This system uses basically strobe lights to trip the signals. It is usually a single strobe mounted on the centerline of the vehicle although it is sometimes integrated into the light bar. The strobe flashes a pattern at a specified frequency to trip the lights. Chris -- ============================================================================= Chris Kinsman KINSMAN@WSUVM1 Washington State University 22487863@WSUVM1 Computing Service Center ckinsman@yoda.eecs.wsu.edu
ckinsman@yoda.eecs.wsu.edu (Chris Kinsman) (04/13/91)
In article <1991Apr12.063837.7120@bradley.bradley.edu> sony@buhub.bradley.edu (David Lennie) writes: >In <1991Apr12.042157.6685@engage.enet.dec.com> moroney@ramblr.enet.dec.com writes: > >>Some systems have a photoelectric sensor aimed at the traffic lanes and a phase >>locked loop circuit that is synchronized to the flashing emergency lights on >>the emergency vehicles. When the PLL detects the flashing lights in a certain >>direction, it turns the light green in that direction. > >Wouldn't this also detect the flashing lights on construction vehicles >or tow trucks? > >Does the sensor simply pick up the presence of any flashing light or >does it confirm that it is actually a police or fire vehicle by >measuring frequency of flashes or something similar? If it does >measure the frequency, wouldn't it be susceptible to error due to >slight variances in the flash frequency caused by low or high battery >voltage in the vehicle? > >I am intrigued (obviously). Explain furthur. The ones I have seen detect a frequency range as well as pattern. It is usually not just the strobes in the light bar but a special strobe designed for this purpose. (This is an option on most new EVs. Chris -- Chris Kinsman KINSMAN@WSUVM1 Washington State University 22487863@WSUVM1 Computing Service Center ckinsman@yoda.eecs.wsu.edu Computing Resources Laboratory 76701.154@compuserve.com
jre@sactoh0.sac.ca.us (Jim Earl) (04/13/91)
In my town, there are devices mounted on the traffic signals that
contain a sensor that picks up the rapid white flashing
hi-intensity strobe lights that are mounted on the local fire
trucks. They work from up to a 1/2 mile away, even during the
daytime. The flashing has to be a specific frequency (very fast, I
don't know the exact frequency, probably around 5 flashes per
second), and of course, very bright. The fire chief is a buddy of
mine, that is how I know.
--
Jim Earl - KB6KCP / home: (916) 729-6825 work: (916) 929-0300 x233
INTERNET: jre@sactoh0.SAC.CA.US
UUCP: {ames | apple | att | sun}!pacbell!sactoh0!jre
or: ucbvax!csusac!sactoh0!jregbell@sdcc13.ucsd.edu (Greg Bell) (04/13/91)
In article <5170128@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes: >transmitter. The receivers tend to be pretty directional, too: aren't >they in pipes perhaps 1" diameter and 6" long? > I've seen this too. What doesn't make sense is that I'd think the truck would have to be in a particular lane to get the thing to trigger. And, emergency vehicles take the "best route", right? Hmm... -- ----------------------------------------------------------------------------- Who: Greg Bell Address: gbell@ucsd.edu What: EE hobbyist and major Where: UC San Diego -----------------------------------------------------------------------------
khan@mrcnext.uiuc.edu (Scott Coleman) (04/14/91)
brian@ucsd.Edu (Brian Kantor) writes: >The "Opticon" sensors in use throughout San Diego County for traffic >light control by emergency vehicles use a photocell in a focusing >assembly that's pointed down the road. They ignore changes in ambient >light levels and look for flash rates of either 10 or 16 hz, which the >bus or emergency vehicle generates with a very bright xenon strobelight. Hmm... Sounds to me like a few parts from Radio Shaft will get you a sure- fire way to minimize the dreaded morning commute! ;-) -- Scott Coleman tmkk@uiuc.edu University of Illinois at Urbana-Champaign "If a software computer consultant believes her gonads are ruled by the moon, then none of us is safe." - Karla Jennings
roger@hpnmdla.hp.com (Roger Petersen) (04/15/91)
Re: home brew traffic light triggerer Generating an 800 MHz signal sure sounds easier than generating a 10 to 16 Hz high power strobe (unless a funky digital code is required). And 800 MHz is also a lot less conspicuous than a flashing strobe. Sounds like a new market for the radar detector manufacturers... People might start to notice, however: "Hey, how come the lights always turn green for Bob, but not me?" (Visions of the Nissan "Bob" commercial.) Roger "Don't try this at home, kids!"
aalonzo@eagle.wesleyan.edu (04/15/91)
>>Some systems have a photoelectric sensor aimed at the traffic lanes and a phase >>locked loop circuit that is synchronized to the flashing emergency lights on >>the emergency vehicles. When the PLL detects the flashing lights in a certain >>direction, it turns the light green in that direction. > > Wouldn't this also detect the flashing lights on construction vehicles > or tow trucks? > > Does the sensor simply pick up the presence of any flashing light or > does it confirm that it is actually a police or fire vehicle by > measuring frequency of flashes or something similar? If it does > measure the frequency, wouldn't it be susceptible to error due to > slight variances in the flash frequency caused by low or high battery > voltage in the vehicle? I worked for a while in the engineering department at Whelen Engineering, a large manufacturer of warning & strobe lights for emergency vehicles. They made a special white, directional, rapid flashing strobe light that would trigger recievers at intersections. The system I believe was developed by Xerox?. What it consisted of was a rapid flashing strobe light (200 - 300 flashes per minute) aimed at the intersection. A reciever at the intersection decoded the high flash rate and turned the proper signal green to allow passage of the emergency vehicle. The flash rate of the strobe on the firetruck could be maintained pretty stable (+/- 3 FPM), and was directional and aimed at the stop lights. It would be pretty unlikely that the random flashes of a tow truck, etc. would match the trigger frequency for the sample period required to turm the light green. I hope this sheds some light on the subject....) ______________________________________________________________________________ Allen Alonzo Computer Service Supervisor Wesleyan University AALONZO@EAGLE.WESLEYAN.EDU
jeh@dcs.simpact.com (04/16/91)
In article <khan.671567418@mrcnext>, khan@mrcnext.uiuc.edu (Scott Coleman) writes: > brian@ucsd.Edu (Brian Kantor) writes: > >>The "Opticon" sensors in use throughout San Diego County for traffic >>light control by emergency vehicles use a photocell in a focusing >>assembly that's pointed down the road. They ignore changes in ambient >>light levels and look for flash rates of either 10 or 16 hz, which the >>bus or emergency vehicle generates with a very bright xenon strobelight. > > Hmm... Sounds to me like a few parts from Radio Shaft will get you a sure- > fire way to minimize the dreaded morning commute! ;-) ^^^^ was this pun intentional?? A buddy of mine (in the LA area, where the same system is used) once decided to try this. The foundation for the project was a Sears automotive timing light with inductive pickup. This got him the strobe, housing, and a condensing lens. A normal timing light only fires when triggered by a signal from the #1 spark plug. He added a simple 555-based timer to do the triggering, a pot to adjust the frequency, and a switch, all mounted inside the timing light case. The power-lead clips, intended for attachment to the car battery terminals, were removed and replaced with a lighter-socket plug. The switch disconnected the 555 circuit and allowed the unit to be used for its originally-intended function. It turns out that the standard condensing lens in the timing light (intended for directing the strobe output onto a small area no more than a foot or so away) was nowhere near good enough to do the job. He experimented with various optics (C&H Sales in Pasadena, with its warehouse full of govt. surplus optics, being somewhat nearby) and actually got the thing to work, after a fashion. Trouble was, the aiming was very finicky, and the Opticon (Opticom?) pickup unit apparently needs to see the required flash-frequency for several seconds. He had envisioned being able to reach into the back seat, pull out this huge chrome-plated buck-rogers-raygun-looking THING, squeeze off a shot at the traffic light, and be done with it; reality was much less emotionally satisfying. He still uses the unit as a timing light, and just smiles when asked what that extra knob is for. --- Jamie Hanrahan (x1116), Simpact Associates, San Diego CA Internet: jeh@dcs.simpact.com, or if that fails, jeh@crash.cts.com Uucp: ...{crash,scubed,decwrl}!simpact!jeh
tmkk@uiuc.edu (Scott Coleman) (04/18/91)
In article <7380024@hpnmdla.hp.com> roger@hpnmdla.hp.com (Roger Petersen) writes: > >Re: home brew traffic light triggerer > >Sounds like a new market for the radar detector manufacturers... > >People might start to notice, however: "Hey, how come the lights always >turn green for Bob, but not me?" (Visions of the Nissan "Bob" commercial.) I just heard that these devices turn all the signals at the intersection RED, thus bringing all traffic to a halt (except for the official emergency vehicle, which of course can go through red lights). So much for that great new market for Cincinnati Microwave. :-(
bender@oobleck.Eng.Sun.COM (I want to be eating rich soup in another town) (04/18/91)
In article <1991Apr17.181300.16991@ux1.cso.uiuc.edu> tmkk@uiuc.edu (Scott Coleman) writes: ->In article <7380024@hpnmdla.hp.com> roger@hpnmdla.hp.com (Roger Petersen) writes: ->> ->>Re: home brew traffic light triggerer ->> ->>Sounds like a new market for the radar detector manufacturers... ->> ->>People might start to notice, however: "Hey, how come the lights always ->>turn green for Bob, but not me?" (Visions of the Nissan "Bob" commercial.) -> ->I just heard that these devices turn all the signals at the intersection ->RED, thus bringing all traffic to a halt (except for the official ->emergency vehicle, which of course can go through red lights). well, you could still have some fun with it! mike -- Won't look like rain, Won't look like snow, | DOD #000007 Won't look like fog, That's all we know! | AMA #511250 We just can't tell you anymore, We've never made oobleck before! | MSC #298726
murray@sun13.scri.fsu.edu (John Murray) (04/18/91)
In article <1991Apr17.181300.16991@ux1.cso.uiuc.edu> tmkk@uiuc.edu (Scott Coleman) writes: > >I just heard that these devices turn all the signals at the intersection >RED, thus bringing all traffic to a halt (except for the official >emergency vehicle, which of course can go through red lights). All depends on how your local boys have set them up. They used to use a system like this in Miami on the Metro buses, turning the lights green ahead of them to keep them moving faster. Of course, your city's milage may vary. -- *Standard Disclaimers Apply*| ---Get Out Of HELL Free!--- John R. Murray |The bearer of this card is entitled to forgive murray@vsjrm.scri.fsu.edu |Himself of all Sins, Errors and Transgressions. Supercomputer Research Inst.| -- D. Owen Rowley
ckinsman@yoda.eecs.wsu.edu (Chris Kinsman) (04/18/91)
In article <18277@sdcc6.ucsd.edu> gbell@sdcc13.ucsd.edu (Greg Bell) writes: > >I've seen this too. What doesn't make sense is that I'd think the truck would >have to be in a particular lane to get the thing to trigger. And, >emergency vehicles take the "best route", right? Hmm... > Actually they don't. According to EVAP (Emergency Vehicle Accident Prevention) manuals all emergency vehicles should stay in the left lane at all time to prevent drivers from pulling over, right into your truck. Consequently if I come to an 4 lane intersection in the left lane and there is a car blocking the leftmost lane I will pass this car in the oncoming lane as opposed to the right. Chris -- Chris Kinsman KINSMAN@WSUVM1 Washington State University 22487863@WSUVM1 Computing Service Center ckinsman@yoda.eecs.wsu.edu Computing Resources Laboratory 76701.154@compuserve.com
ckinsman@yoda.eecs.wsu.edu (Chris Kinsman) (04/18/91)
In article <1991Apr15.090530.41753@eagle.wesleyan.edu> aalonzo@eagle.wesleyan.edu writes: > >I worked for a while in the engineering department at Whelen Engineering, a I am glad you don't any longer. We have finally given up on Whelen for most of our needs. We purchased an integrated light bar control/siren from them that can't be heard 10 feet away inside a car. We have had it replaced twice and are now removing it for a Federal. -- Chris Kinsman KINSMAN@WSUVM1 Washington State University 22487863@WSUVM1 Computing Service Center ckinsman@yoda.eecs.wsu.edu Computing Resources Laboratory 76701.154@compuserve.com
ckinsman@yoda.eecs.wsu.edu (Chris Kinsman) (04/18/91)
In article <1991Apr17.181300.16991@ux1.cso.uiuc.edu> tmkk@uiuc.edu (Scott Coleman) writes: > >In article <7380024@hpnmdla.hp.com> roger@hpnmdla.hp.com (Roger Petersen) writes: >> >>Re: home brew traffic light triggerer >> >>Sounds like a new market for the radar detector manufacturers... >> >>People might start to notice, however: "Hey, how come the lights always >>turn green for Bob, but not me?" (Visions of the Nissan "Bob" commercial.) > >I just heard that these devices turn all the signals at the intersection >RED, thus bringing all traffic to a halt (except for the official >emergency vehicle, which of course can go through red lights). > >So much for that great new market for Cincinnati Microwave. :-( It actually depends on how the system is programmed. I have seen Opticom systems by 3M that can do both. Chris -- Chris Kinsman KINSMAN@WSUVM1 Washington State University 22487863@WSUVM1 Computing Service Center ckinsman@yoda.eecs.wsu.edu Computing Resources Laboratory 76701.154@compuserve.com