williams@srcsip.UUCP (Susan Williams) (05/02/86)
In article <992@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >In article <4839@topaz.RUTGERS.EDU>, josh@topaz.RUTGERS.EDU (J Storrs Hall) writes: >> What's the circuitry behind the buried-wire car detectors at >> stoplights? Technical details please. > > [Technical details] 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.
hank@masscomp.UUCP (Hank Cohen) (05/07/86)
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
jeffj@sfsup.UUCP (J.S.Jonas) (05/07/86)
> In article <4347@srcsip.UUCP> williams@srcsip.UUCP (Susan Williams) writes: > [will it be used for] > 55 mph speed limit compliance? > Hank Cohen I took a tour of the Sperry plant in Great Neck, NY where they were testing the Long Island Expressway/Northern State Parkway/ Grand Central Parkway/and neighboring streets traffic control system. The traffic sensors, message boards and traffic lights around the major roads are all coordinated by the system. In the main control room, there is a big map of the roads with indicators all over. CRT readouts give average speed and traffic density. The idea is that a traffic jams can be detected and traffic can be diverted by warning motorists miles ahead with the message signs (which are on the highways and entrances). The traffic signals on the neighboring streets can be modified to handle the increased that use some local roads between the two). The signals are carried by buried cables along the highways, unlike another system (in Washington DC I recall) where telephone lines were used. The buried cables have a higher initial cost, but the maintenance costs are less than the telephone lines. The telephone based system was shut down because leasing the lines became too expensive. The entire system should soon be in place and operating. I wish the operators well, and hope the system lives up to its expectations. Jeff 'still a Long Islander at heart' Skot {ihnp4 | allegra | abosgd} attunix ! jeffj PS: Even if your speed can be detected by the sensors, you can't get a ticket because a person has to witness the crime, or something to do with an officer observing the crime. This is why the New Jersey Turnpike doesn't give you a speeding ticket based on your travel time. The toll ticket you get when you enter the Turnpike has the time on it, so if you arrive at your destination too early, it's obvious that you went >55 MPH, but legal complications don't allow them to ticket you (i.e.:What if the clocks are incorrect?)
philm@astroatc.UUCP (Phil Mason) (05/07/86)
In article <4347@srcsip.UUCP> williams@srcsip.UUCP (Susan Williams) writes: >In article <992@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >>In article <4839@topaz.RUTGERS.EDU>, josh@topaz.RUTGERS.EDU (J Storrs Hall) writes: >>> What's the circuitry behind the buried-wire car detectors at >>> stoplights? Technical details please. >> >> [Technical details] > >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. Yes, I've seen it done. They use a very slender version of a "Ditch Witch" type digger. It's kind of like a chain saw, but with asphalt-proof teeth and special wheels to guide it. I wasn't able to get a real close look, but it seems they only go 2-3 inches deep. After laying the wires, they add some sealing caulk. -- =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Kirk : Bones ? Phil Mason, Astronautics Technical Center Bones : He's dead Jim. {Your Favorite System}!uwvax!astroatc!philm My opinions are mine and not necessarily those of my employer. (I would like to think that my employer believes in them too.) :-) =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
larry@kitty.UUCP (Larry Lippman) (05/11/86)
In article <986@masscomp.UUCP>, hank@masscomp.UUCP (Hank Cohen) writes: > > 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. These detectors are used for vehicle speed monitoring on heavily- traveled expressways, but NOT for speed law enforcement purposes. The detectors are used for traffic control purposes, and information from the detectors may be used to change the timing on traffic signals admitting traffic on entrance/exit ramps, etc. Knowing the average speed of traffic on a road will also provide advance notice of traffic accidents, vehicle breakdowns, etc.; obviously if the _normal_ average speed on an expressway is say, 50 MPH, and all of a sudden it is 5 MPH, that is a pretty good indication of a problem requiring the attention of police! Most major cities have some type of centralized traffic control center which allows remote control of traffic signals, remote monitoring of traffic, etc.; such control centers are also found on major bridges and tunnels. So, these speed detectors are monitored in those control center locations. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York ==> UUCP {decvax|dual|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry ==> VOICE 716/688-1231 {rice|shell}!baylor!/ ==> FAX 716/741-9635 {G1, G2, G3 modes} seismo!/ ==> "Have you hugged your cat today?" ihnp4!/