HI all, me again (don't groan)
Can someone help to settle a dispute? On traffic lights there are little grey boxes on top of traffic lights which look a lot like sensors. Is this what they are? I have had a number of ideas...some as stupid as the next:
a) sensors to control lights
b) sensors to detect pedestrians
c) red light cameras (I am doubtful about this one; if they were capable of that, why put up the massive ones that are definitely cameras?)
d) (My personal favourite...) CCTV cameras......
Needless to say, I really want to know what they are now...so...WHAT ARE THEY? Please...
Many thanks...
Adam
--
After death, hair grows but phone calls tend to taper off
|
they Are IR sensors to detect whether ther is a car waiting at the lights this adds the advantage that they to do stop other traffic if no car is waiting on the red lights. Regards Peter
|
|
|
I think these are IR sensors to detect vehicles which are not picked up by the inductive loops buried in the roads.
Some vehicles eg motorbikes, aluminium bodied cars, cyclists do not contain enough ferrous material to be detected by the loop and thus they can get stuck on a red until something else comes along. (not that a red light will stop most cyclists but that's another thread!)
No longer do we have the opportunity to step out and stand on the pressure pads as in my yoof.
I do know that in USA some bikers buy strong magnets which they fasten to the bottom of the bike to avoid this happening, but never heard of it in UK. Others could be better placed to know if this observation is correct with bikes in UK, but the presence of sensors may explain why this might not be so common a solution in UK.
FWIW that's my 2p anyway.
FiF
|
Either IR or microwave sensors as found here www.microwavesensors.com/TC26-B.html
--
groups.msn.com/honestjohn - Pictures say a thousand words.....
Reply |
Report as offensive
| Link
|
|
If the sensors are the same as those used on temporary lights, it's worth knowing that if the lights are sensor controlled rather than time controlled (they can be switched between the two) and you coast slowly up to a red light hoping to catch the green without stopping, you might not be going fast enough to trigger the sensor. A backward and forward waving of the hand directly in front of the sensor box will change the lights.
|
|
All they are is Infra-red heat dete4ctors, they simply pick up the heat from the engine and theyreby change the lights in your favour if no-one else is waiting at the other lights.
|
|
A few years ago I worked as an engineer (mechanic) for a national company that manufactures, supplies ,installs, and maintains temporary traffic signals, usually for local council's etc. The equipment I worked on at that time didn't include any sort of heat detector. The boxes on top of, or just under, the lights contain a crude sort of radar/sensor (can't remember the tech term). An approaching vehicle is detected by the bouncing and measuring of em. waves etc. In theory this moving vehicle detector should work well, but it only does so when traffic is light, ie several vehicles per hour. In heavy traffic the system can't really cope as for one reason the legal minimum time for a green traffic signal to be displayed is about 12 seconds. In most situations the signalling set by a timer.
|
|
Yes some of the units are Radar Doppler units that retect a crued measurement of speed and trigger the lights. These are mostly used where the road is reduced to a sigle lane i.e. narrow bridges and the like, this is to allow approaching emergency sevice to trigger the lights and forcea red against oncomming traffic. I know of a couple around here that the locals trigger them to save waiting. Regards Peter
|
They could be the reciever that picks up the transmision of an approaching bus, which then gives priority to the bus over other traffic.
rustbucket
|
|
I'm pretty sure that most of the sensors in Leicestershire are set to detect cars and immediately switch to red!!
|
I'm pretty sure that most of the sensors in Leicestershire are set to detect cars and immediately switch to red!!
Yes it seems that way, most countries use lights to improve traffic flow in the uk we use them to discourage use of the car
rustbucket
|
|
|
|
not that a red light will stop most cyclists...
Hmm... some of us have been known to wait for the complete sequence of light changes to occur at a quiet junction before realising that the sensor hasn't sensed us.
|
>> not that a red light will stop most cyclists... Hmm... some of us have been known to wait for the complete sequence of light changes to occur at a quiet junction before realising that the sensor hasn't sensed us.
With acknowledgements to Basil Fawlty Towers Communication Problems
"a cyclist who waits at lights! we should have him stuffed!"
Only kidding W!
|
"a cyclist who waits at lights! we should have him stuffed!"
I'd modify that to say a cyclist with lights. I'm appalled at the behaviour of 99 per cent of the cyclists I see. Riding on pavements and lack of lights are the main offences, but that's a topic for another thread.
|
|
|
|
|
Do they detect density in traffic...heres why i think why
using the ones in the town, when you press the button the lights seem to make you wait until most traffic has past buy if its busy, when it quitens down or there is a gap in the traffic, then they change to red and let you cross.
When i have used them and there is no or little traffic they change to red instantly.
so are they to aid traffic flow at pedestrian crossings?
--
1983 (A) Vauxhall Astra 1.3L
1993 (K) Vauxhall Cavalier 2.0i GLS
1999 (T) Renault Laguna 1.6
|
Our local authority have started to fit equipment to some traffic light controlled pedestrian crossings that disables the pedestrian push button as a bus fitted with a tag approaches, it overrides the button for long enough for the bus to pass over the crossing unhindered.
This can save a good few minutes at certain times of day on some routes and helps service reliability.
PP
|
Thanks for all of your replies - I think we can safely assume that they are sensors of some sort - infra red or not. Unfortunately, my friend is insistent that they are CCTV cameras. When asked who is watching these hundreds of cameras in one town he comments "No-one - they're just handy to have at a crash" The sad thing is - I can see his logic.
Thanks
Adam
--
"Give Way"? Wait....I know this one...give me a minute
|
Phew ! The pure guesswork contributions in this thread take on the mantle of authority and hide the true facts and genuine contributions.
The boxes on top of traffic lights at road junctions that face the oncoming traffic are microwave vehicle detectors, variously called MVD's and Doppler radars (NOT infra-red !!!).
The design dates from portable signals (roadwork's ones) and was developed at a time when they were being updated from two lamp ones (red, green) to the modern three lamp ones (mid-sixties or so). Later, as traffic engineers found they were cheaper than loops, they migrated to being used on fixed signals. Not so well known is that traffic control is less precise than when using loops (as one contributor stated) --- probably not well publicised in the manufacturer's specification either.
The originals used a frequency between 10 and 11 GHz (Xband) but that has since moved to a higher frequency (now somewhere in the 13-22 GHz region I think).
The MVD's have direction sense, (can distinguish between approaching and receding vehicles) and are usually set to trip for an approach --- the Gatso is likely to have benefited from their design and be using something similar.
Receding vehicles often provide a stronger signal than an approaching one and this can swamp the MVD causing blindness to an approaching vehicle. The two signals use the same amplifier channel in such simple radars -- the biggest signal wins. Thus how the radars are sited and aimed is quite important.
Return from heavy rain can also be a problem. As can walking pedestrians. This latter can be countered/attenuated by the use of processing but not a 100% as to improve it more risks the non-detection of slow vehicles. Thus crawling up to a red light while waiting for it to change is not a good idea (again already mentioned).
In regard to the infra-red references in this thread, I very much doubt IR is used for traffic detection. Technically it is not very suitable. There has been talk of its use to detect pedestrians on crossings, (maybe?) but it not as good as Doppler and that with non-directional sense can be cheap.
Redlightzone is right about the ones fitted to pedestrian crossing lights. The idea is to switch those lights during a traffic lull if possible.
|
Ok, now you've all cleared that one up, what are the two parallell lines of shiney squares in front of the stop line at traffic lights for? Surely they're not just marking where people should cross? Are they for the traffic light cameras to "bounce" off to tell if you've jumped the lights?
Thanks
|
Much too early for me to be out and about yet. The streets are not aired.
More seriously, I have not seen them. I will have to go and have a look sometime. But it is some time since I was involved. Talk then was of names like Panda and others to indicated the degree of sophistication used. Google might help.
|
|
|
And while sorting out mystery objects, what are the little blue boxes one sees isolated at the side of main roads in the country?
They look a bit like those belt massager machines on stands that are supposed to trim inches off your waist, but pointing downwards at a rather drunken angle.
|
|
|
Ok, now you've all cleared that one up, what are the two parallell lines of shiney squares in front of the stop line at traffic lights for? Surely they're not just marking where people should cross? Are they for the traffic light cameras to "bounce" off to tell if you've jumped the lights? Thanks
>>
Are you referring to the studs which officially delineate the pedestrian crossing part?
see highway code rule 18, ie pedestrians should cross between the studs.
DVD is this the correct link to TSGRD2002?
www.hmso.gov.uk/si/si2002/023113ce.gif
|
Cliff, I think the blue cameras you are on about are TrafficMaster ones which are harmless.....so far. Apparently they read the middle three digits of your licence plate and then warn people subscribed to the service if there are traffic jams...If I am wrong, someone please correct me
Adam
--
"Give Way"? Wait....I know this one...give me a minute
|
|
I don't think they are cameras - at least they don't appear to have any openings in them. They are on poles about 3 feet off the ground, are rectangular, about the size of a biscuit tin, painted pale blue.
|
In that case then, that's my theory out of the window. The ones I see are on bypasses and are dark blue and have a black face on them like a sensor. They range from 8ft high to about lampost height. If the ones you see are pale blue and shorter, I'm afraid I don't know what they are. Someone else will be along soon though and will be able to help you.
Cheers
Adam
--
"Give Way"? Wait....I know this one...give me a minute
|
Cliff,
Are the boxes on bus routes? A few years ago my local bus company installed anonymous looking boxes on some major bus routes. They were usually mounted on a lamp post or telegraph pole but not neccesarily near a bus stop. As a bus with a transmitter passed the box a signal was sent to a control center informing the 'management' as to it's position on the route. Part of the plan was to was to transmit waiting time information to VDU's at bus stops along the route. I don't know if the system is up and running yet.
|
I think the best way out of this one is to grab a picture of the 'offending' item for all to see!
How you do it is entirely up to you ;-)
--
groups.msn.com/honestjohn - Pictures say a thousand words.....
Reply |
Report as offensive
| Link
|
|
|
|
|
ive been reading, with interest, the various opinions on the little grey boxes on lamp posts and have to disagree with the view that they are ifra-red/sound sensors or such like for control of traffic lights/traffic flow. i live on an island on the west coast of Scotland with one set of traffic lights and no traffic congestion and yet these little grey boxes are everywhere. i haven't a clue what they are doing and that is how my search found me on Honest Johns site. i have phoned the council, the local newspaper and discussed them with the police and all deny any knowledge of their purpose. personally, i was suspicious that google maps had something to do with them or perhaps traffic counting but still cant get an answer. if their purpose is so innocent why does no one know what they are for
|
|
Lamp posts? Street lights?
The OP was about traffic signals' motion sensors.
If you post a photo, I will tell you what it is.
Edited by Hamsafar on 02/11/2014 at 17:31
|
|
QUOTE:....""Some vehicles eg motorbikes, aluminium bodied cars, cyclists do not contain enough ferrous material to be detected by the loop and thus they can get stuck on a red until something else comes along. (not that a red light will stop most cyclists but that's another thread!)""
Most cyclists are law-abiding, For every cyclist that ignores a red light there's a car driver who pulls out of a junction in front of a cyclist!
|
|
Those last ten years seem to have flashed by...
|
|
Traffic light cameras are usually normal 18 ins cubic yellow boxes as per Speed Cameras. They are positioned to look down on a junction, to take photos, triggered by the sensors. (In the grey boxes that don't have lenses?)
|
|
|
|
|
If they're the big grey boxes they are putting up in Manchester, about 6x2 foot,it's to stop crazy motorists who got caught by the speed cameras shooting them out.
|
|
|
