The Speed Camera Thread - Volume 13 - Dynamic Dave

THREAD CLOSED, PLEASE CONTINUE DISCUSSION IN

"The Speed Camera Thread - Volume 14"


www.honestjohn.co.uk/forum/post/index.htm?t=17068


For the continued discussion of all things pertaining to Speed Cameras.

Volume Twelve filled up.

This is Volume 13, 12 is closed.

There is no need to repeat anything since earlier volumes will not be deleted, although I am quite sure that this will not stop you.


--
Dynamic Dave
Back Room Moderator

mailto:dave_moderator@honestjohn.co.uk
Thelwall Viaduct speed cameras - davo
Are these cameras working or not? Every time I trundle thru at 40mph, seems loads of cars are doing 60-80mph?
Thelwall Viaduct speed cameras - LongDriver {P}
I know people who've been prosecuted through that section.

They are SPECS and are working...most recent victim I'm aware of got his notice through 3 weeks ago.

Stick to 40mph...it's unusual to be able to get through any quicker most of the time anyway!

I just set the cruise at 40 and wait til I've passed the last scamera before speeding up.
Thelwall Viaduct speed cameras - Pugugly {P}
These still there ?I am passing through next Sunday on the way to a work related conference.....they were there last Novenber what is happening ?
Thelwall Viaduct speed cameras - LongDriver {P}
Bridge bearings on "old" Thelwall viaduct are being replaced again...yes they were only done a couple of years ago!

They've just started replacing them...the closure of the bridge to date has been for safety as the bearings have failed.

Problem with the steel used in the manufacture of the old bearings.

Another £30 million to replace them again I believe...will take approx 18 months!!!! FROM NOW!
Thelwall Viaduct speed cameras - davo
Thanks, it's mainly on a Sunday when I go thru when it is less busy. By the way what are SPECS?
Thelwall Viaduct speed cameras - LongDriver {P}
See this link for details of the SPECS cameras:

www.speedcheck.co.uk/specs.htm

They're the ones with the fluorescent yellow or orange boards behind them, which they put there so you can't argue in court that you couldn't see them!
Thelwall Viaduct speed cameras - BobbyG
Guys apologies if this has been covered before but have spent the last half hour scrolling through thread after thread and can't find an answer (Even the thread that consists purely of Gumshot's opinions).

On a bog standard roadside Gatso, I was passing one at 25mph when it flashed as there was a car coming the other way (30mph limit|. So therefore I assume it was a camera that works both ways.

If that is the case, why is it only the rear of the camera that needs fluorescent markings and not the front? Also, I thought there was an issue at one point about taking front pictures due to civil liberties etc - is that not the case anymore?

Any clues?
Thelwall Viaduct speed cameras - Altea Ego
BobbyG

The speed of the other car caused the radar to activate, it cant discriminate between a rising doppler or a falling doppler, it just measures doppler shift, so it will activate the flash either way, but only the car traveling away from it will be prosecuted.
Thelwall Viaduct speed cameras - AngryJonny
I've been thrown by this before. Several times I've been through cameras within the limit and they've flashed. I've never heard anything afterwards and I could only assume that it was something like that.
Thelwall Viaduct speed cameras - BobbyG
RF, Thanks for that, however do you not get speed cameras now that do both ways? Or is it as you say that it does measure it both ways but only prosecutes one way? Why the white lines on both sides of the road? Is that just to prove in the 2 images that it was the other car that was going too fast?
Thelwall Viaduct speed cameras - No Do$h
If you are really fed up with Gatsos, how about getting a metal bin lid (the sort you get on incinerator bins) and tying some rope to the handle. Stand in front of your target Gatso and swing the bin lid around your head as fast as you can. Within a couple of minutes, no film left! Allegedly.

Move on to next Gatso and repeat.

Not illegal, in much the same way that parking your car in fron of a Scamera van and opening the boot to obstruct the camera isn't illegal. If they point out that you are parked on a "clearway" you may like to point out that any pics they take that day are illegally acquired evidence on the same grounds.....

It's great what you can trawl up when you search the web. Anyone tried either of the above?
Thelwall Viaduct speed cameras - Dynamic Dave
BobbyG,

The only ones that will get you as you approach them, AFAIA, is the Truvelo, and is painted blue.

Reason why white lines are on both sides of the road is to prevent camera dodgers from moving to the other side of the road as they pass the camera. Also it is to catch people who happen to be overtaking another car where the camera is. The car being overtaken can be proved innocent of speeding by the white lines.
Thelwall Viaduct speed cameras - Altea Ego
Yes correct DD, Truvelo (the one painted blue with the infra red flash) is the only one to knick you "in your face" so to speak. Truvelo works on sensor wires in the road (mostly)

Unless you count specs of course, which can photo id you from the front or back, mostly set for front photos.
Thelwall Viaduct speed cameras - Flat in Fifth
Yes correct DD, Truvelo (the one painted blue with the infra
red flash) is the only one to knick you "in your
face" so to speak. Truvelo works on sensor wires in the
road (mostly)
Unless you count specs of course, which can photo id you
from the front or back, mostly set for front photos.

>>

plus camera vans / cars etc etc
A41 West brom to Brum - PoloGirl
The speed camera boxes have been up since about May of this year, and they finally got round to putting the lines on the road this week.

Is it just me, or are they totally wonky? In two cases, the line is so unstraight that it just heads for the kurb.

Question is, do you have to drive over all the lines for the camera to work out what speed you're doing? If I drive straight but the line is wonky, I'll only cover about the first 5 lines.

Hmmm...

Speed Cameras on A14 A1-M1 link? - patpending
I noticed a different sort of speed camera on the A1-M1 link (which is apparently referred to as "A14" though I thought that was the Old North Road)!. It looks a bit like a single traffic light and faces forwards. I saw three so I imagine they may be linked and measure average speed between them...

I have searched the site for "speed camera" but I get too many answers. can you point me at a description of these cameras and how they work?

thanks for any help

pat

Speed Cameras on A14 A1-M1 link? - mmm-five
The only static cameras I know on the road are at the Kettering junctions and are TruVelo cameras.

www.ukspeedcameras.co.uk/truv3.jpg
Speed Cameras on A14 A1-M1 link? - patpending
thank you very much mmm-five, the site you mention does show a "truvelo" camera which appears to be what I saw, and these like GATSOs record the speed at the actual location rather than the time between the two.

evidently there are in excess of 10 speed cameras on the A14 (=new A1-M1 road and A604) so I an only presume that the name "truvelo" is from the phrase of the Ferrari driver "i am in-a deepa truvelo!")

very useful site, apologies if I have missed an existing thread spelling this all out.

pat
Speed Cameras on A14 A1-M1 link? - Altea Ego
dont get them confused with the traffic master detectors.... they have some new types on that road between the m1 and the stamford turn
Speed Cameras on A14 A1-M1 link? - No Do$h
Do also watch out for a white transit van parked on your side of the road but facing you, anywhere in Northamptonshire, especially around the A14, A605 and A43. The rear is fully signwritten, but by the time you see that, the scameras have nabbed you.

try www.northants.police.uk/safetycamera/full_month_li...m for possible locations.
Classic Malfunction of a Gatso - buzbee
I saw a classic 30 mph Gatso malfunction in Brighton. I was approaching it from behind whilst two vehicles were approaching from the front. The far one was a large red van, the nearer one was a Mini sized vehicle. No other vehicles were in view.

This type of radar is such that the signal returned by the van can be so large as to blot out the signal returned from the Mini until the Mini gets quite close, subject to the particular van and Mini design as looked at from a radar point of view.

The Gatso was on my side of the road and the mini was accelerating towards it at a speed of about 40 mph. It almost got past the Gatso when the first flash fired and by then was so far to the side of it that it is most unlikely it will appear in any photo.

Meanwhile the red van was in full view and so I expect the photos to show a single large red van as the only vehicle seen by the radar and to have printed on them a speed figure of 40mph approx. This is interesting because for the van on the white markings the recored speed would be incorrect.

What the van driver probably does not know, and what I do because I was careful to look, in this case, was that the van had not quite reached the start of the road markings by the time the two flashes had occurred. So the speed of the van is indeterminate. And, the van-man should not get a brown envelope. But how sure are we that some 'untrained', (to put it politely) person will not try it on ?

Only if the police are obliged to supply the pictures in the brown envelope are we the public to know that they would not send one out in this case. And if they did, the recipent would have the means of a defence/protest without the worry of going to court.

I think a gross liberty is being taken of the public by the police with their high handedness of not including the picture evidence. It allows them a sloppy behaviour with little or no come back. If the envelope is challenged, they can just drop the procedure.

Classic Malfunction of a Gatso - paulb {P}
Whereabouts was that? Only reason I ask is that if it was the one in Old Shoreham Road by the railway bridge, I've seen that go off when a sparrow flew in front of it. Nice reliable bit of kit, that.
Classic Malfunction of a Gatso - Peter D
Noraml Gatso camera brown envelope practice is to only prosecute any vehicle photographed from the rear and the camera on your side of the road. Your comment on van signal swomping the mini is not valid as the Gatso is triggered by the Doppler effect not the size of the signal. If the Van was doing 30 then its Doppler in terms of frequency offset from the carrier is smaller than the Mini doing 40 so the Mini would be detected thus the flash. I hope that clears it up for you. Regards Peter
Classic Malfunction of a Gatso - buzbee
I think you have missed my point. The mini triggered the camera at 40 mph because it was closer and so its signal was then larger than the van. I know a lot about Doppler and this is a true statement of what can happen.
Classic Malfunction of a Gatso - buzbee
Where was the Gatso:-

Coming over the top from Falmer and dropping down to Brighton you pass through a set of lights in Saltdean going down the hill.

They moved the Gatso back up the hill to just before the bend because it was not collecting enough money where it was previously -- my cynical view. You need brakes on in top gear to get below 30. A moments in attention and . . .

Birds ought mostly not to trigger it. It depends on what signal processing the designer used. Doppler signals (audio sort of frequency) that flutter need to be rejected but it depends on how good the radar designer was and it will never be perfect but can be very good. One Canadian hand held device was excellent.

I have not seen the circuit diagram for a Gatso and so cannot comment on that part of it.


Posts speed to correct thread shock - patpending
Oh great Mods!

thanks for moving my questions to their friends in the right place!

pat
Classic Malfunction of a Gatso - GJD
Only if the police are obliged to supply the pictures in
the brown envelope are we the public to know that they
would not send one out in this case. And if
they did, the recipent would have the means of a defence/protest
without the worry of going to court.
I think a gross liberty is being taken of the public
by the police with their high handedness of not including the
picture evidence. It allows them a sloppy behaviour with little
or no come back. If the envelope is challenged, they can
just drop the procedure.


It does seem very strange that (as I understand it) you have to enter your guilty or not guilty plea without being allowed to see the evidence against you.

I haven't managed to find out whether that's how it works for all crimes though. I have always imagined that someone entering a plea in court has seen the evidence by that point, but I may be wrong.

GJD
Classic Malfunction of a Gatso - buzbee
Yes by the time it gets to court the evidence will have been available to the defence. Of course, in the case of the Gatso, it is then too late to avoid the case, unless the prosecution withdraw or something like that. So what you are faced with in the brown envelop is 'pay up or see yourself in court'. Just the friendly approach you might expect ! ! !
Classic Malfunction of a Gatso - pdc {P}
Nice quote from the man at the AA at the bottom

news.bbc.co.uk/1/hi/uk/3158184.stm
Classic Malfunction of a Gatso - buzbee
What bugs me is, on one hand you have the guy who, due to a moments inattention, does a 36 in a 30 past a Gatso and gets a ticket with no excuse accepted, and on the other, there are ones who, once they have got past, do silly speeds like 50 in conditions that are hazardous. The Gatso is useless as a curb on them. The same type shows you how fast he can go round country lane bends and when you meet him on a bend coming the other way his wheels are always a foot over your side of the road.
Classic Malfunction of a Gatso - John Shelton
Lots of the opinions expressed on here about how gatsos and truvelos work are wrong. The truvelo works purely off 2 sets of wires buried under the roads surface and times you between each one. In our county any speed of 7 mph over the limit is prosecuted. The flashes used on truvelos are not infrared at all, they are merely a magenta coloured fliter fitted in front of a white light flash bulb because the home office specified that white light could not be used in forward facing shots due to it causing drivers temporary blindness. Truvelos have 2 different sets of markings . One set in front and one conventional secondary set behind, for the very simple reason that the camera can be unbolted and rotated inside the housing to face the rear. if it had the elongated set of marking you all associate with gatsos IN FRONT of the camera all the markings would be obscured by the car and so would be worthless as a secondary check on speed. Therefore 3 narrow white lines are used and the photo mUST be taken exactly on the middle of the 3 narrow white lines in frontal shots. Truvelos are acccurate to 200 mph and are normally calibrated up to 188 mph If 2 cars are shown passing the markings IE if an overtaking situation occurs the film is simply binned.no argument! Gatsos have a known fault in that they are affected by low speed high sided HGV's which causes them to flash when there is a slow or stationary qeue of traffic in front of them and a high sided HGV passes in the opossite direction, This is a well known issue and any film of this situation is also binned The secondary markings in this case are alsways checked because the film readers are aware of this fault and can actually see by the distance car wheels have travelled from one white line to the next how fast (or in this case how slow) a car is travelling.
Classic Malfunction of a Gatso - GJD
because the home
office specified that white light could not be used in forward
facing shots due to it causing drivers temporary blindness.


Shame they didn't think of that for oncoming traffic on the other side of the road from a Gatso. The first flash instinctively catches the attention just in time to get the second flash right in the eyes.

Oh well, doesn't happen that often I suppose.
Speed Cameras and a thank you - Kevin T
Cheers for the advice on cold starting a diesel (thanks Richard W & JC). I would have been taken away by men in white coats if it had not been for a proper glow plug ratchet spanner but all 4 glow plugs are changed and it started first turn at 5.20am this morning. Regarding speed cameras I am perfectly happy travelling at the speed limit but it seems some people who follow me are not (must lead busier lives) and am occasionally pushed (not literally) to speeding a little. Does anyone know if the law states that 1. Speed cameras must be placed in an area which is lit at night. 2. They must show the speed camera sign before the camera? Also there is a speed camera after the M67 before Hollingworth and the Penines on a spot of dual carriageway (which is still 30mph) but the camera is painted green. Are some speed cameras adopted by different groups etc if not why the colour change? It does blend in with the hedge! Thanks!!!!
Speed Cameras and a thank you - daveyjp
Those cameras are real ********. I used the Woodhead Pass a few weeks ago to take my parents from Manchester Airport to Sheffield - using the road you mention at night. It's a good job my dad was with me as he told me where all the cameras were. As you state they are not yellow (the local police obviously don't want a cut of the money therefore they don't have to be) and to make it worse they are grey/green and hidden in the bushes.
Speed Cameras and a thank you - Kevin T
There will be yellow hedges next to match the Police ones!!! Oh well.... eyes glued on the speedo!
Speed Cameras and a thank you - RichardW
There is no law that the cameras have to be visible / signed / in lit areas / at accident black spots etc - only guidelines for the 'netting off' scheme. In theory forces that do not follow the guidelines can be removed from the scheme. I can just see that happening!

I believe there is a groundswell of opinion starting to rise against speed cameras, and with an incresing number of people returning unsigned NIPs and asking for their day in court, the system is going to collapse in the not too distant future.


RichardW

Is it illogical? It must be Citroen....
gatso confusion - apm
I did look through the previous speed camera threads, but there was so much I couldn't find my answer. Any help appreciated!


I was flashed yesterday on the A29 in Pulborough, W Sussex. I't's single carriageway (no central reservation), the gatso (for 'tis one of those) is on the edge (nearside) of the northbound carriage way, and there are lines on each side of this carriageway. I was travelling SOUTH , where there are no lines, and I'm sure it flashed me (I thought once only), as no car was obviously speeding going North. My understanding is that gastos take you from behind (as it were), and need the lines in shot for calibration. If I'm coming towards the camera, can it even get me in shot, and if so, can the lines from the northbound half of the road be used against me?

If I was caught, I will raise my hands and pay*. Just curious really.

*my only defence is that that section of road switches from 60 to 40 to 30 to 60 again in the space of about a mile, and is quite confusing really. And I was doing 42 max. And my speedo over-reads by about 5mph (at least), so that's not too bad really.

TIA,

Alex.
--
Dr Alex Mears
Seat Leon Cupra
If you are in a hole stop digging...unless
you are a miner.
gatso confusion - pdc {P}
If a standard GATSO camera flashes when you drive at it, then it means that it is not a live camera, and has a cheaper radar unit in there which can not tell which direction you are travelling in. It simply acts as a deterant.

However, be aware that the camera units can be moved around, and although it may be a dummy today, tomorrow it could have the more expensive live unit in the box.
gatso confusion - apm
Cheers, pdc.

That is interesting. And pretty cunning, really!


--
Dr Alex Mears
Seat Leon Cupra
If you are in a hole stop digging...unless
you are a miner.
gatso confusion - smokie
Not so sure about this pdc. I don't think the powers-that-be have the choice of cheap or expensive units. Or that they could be bothered with installing cheap units to act as deterrent.

When approaching a facing Gatso it sometimes triggers. Usually when you are speeding. Which seems reasonable.

I've only ever seen it flash once when approaching head-on. Which means it's taken it's first picture because it detected someone over it's limit. It doesn't bother with the second as it knows you are going the wrong way.

And as they are designed solely to take a picture from behind there is nothing more can be done.

If, however, you were doing the same speed with the camera behind you, you'd be nicked.
gatso confusion - pdc {P}
Check out the following links

www.speed-trap.co.uk/Accused_Home/Gadgets/Gadgets_...m

www.checkyourspeed.org.uk/index.cfm?method=faq (click on the How Many Cameras Are Live link)

gatso confusion - pdc {P}
For those who can't be bothered to follow the links I just posted

The Dummy GATSO
Dummy GATSO's are a great deterrant. They look just like the real thing, they flash just like the real thing. They just don't take any photos. The camera is typically the most expensive part of a gatso installation, followed by the cost of the radar unit. GATSO can supply a cheaper, self-regulating radar unit that will hook up to the flashgun and fire it when a vehicle passes the camera travelling above a set speed. The dummy radar units are much simpler, and measure speed less accurately then their full-cost counterparts. Dummy GATSO units can be set to flash either once (which gives the game away) or more likely, twice (thus mimicking perfectly a fully operational unit.)

and

According to Chief Inspector Phil Groves (ACPO), the ratio of live units to dummies in the UK in 1999 was 1 in 8. In other words, when you tear past one of those grey boxes, there's a 1 in 8 chance that it's loaded. This is because the flash and the radar unit are cheap, but the camera units themselves are prohibitively expensive. So dummy boxes can have the radar and flash in but no camera, which can give the effect of having been caught, but without any photo actually being taken
gatso confusion - volvoman
It's an often used argument that speed cameras are all about revenue raising not reducing accidents - if this is true why on earth are there dummy cameras set to act as a deterrent and why aren't there many more cameras ?
gatso confusion - smokie
Thanks PDC, I stand corrected...
Am I in trouble? - Jase
Not sure if this should go straight into speed camera thread? D will no doubt move it if so.

On saturday I was going along a dual carriageway on in Bournemouth. Its a 50mph zone. Passed a speed camera doing almost exactly 50mph at the same time as being passed by a car going significantly faster. Speed camera flashes. Oh dear.

Presumably the speed camera will have a picture of my car and the faster car (that caused the camera to trigger) in the frame? How does the speed camera know which of the two is guilty?

How do these cameras work and can someone reassure me that the correct car will be identified!

Thanks very much



Am I in trouble? - volvoman
The white lines on the carriageway surface will show which car travelled further at the time and hence faster.
Am I in trouble? - volvoman
I should add that I think the cameras actually take 2 photos in succession.
Am I in trouble? - Wilco {P}
Ah - the Wessex Way no doubt. There was as lot on a previous camera thread about this bit of road.

As V-Man says, distance travelled between the 2 shots is what they use to calculate your speed. So you will be OK as long as "almost exactly" means what it says :-)
Am I in trouble? - Dynamic Dave
The white lines on the road will distingush who was speeding. Two photos taken, the speed can then be worked out from the distance between the lines in pic one and pic two.


ps, Yes, I will move this to the speed camera thread later
Am I in trouble too? - PoloGirl
And have a got a reasonable excuse...?

Travelling to uni in the big red frog (no I still haven't got my polo back!)... me in the right hand lane, a big lorry in the left hand lane.I am beside the lorry due to weight of traffic and having just left a roundabout.

Just as we approach s************ lines on the road, the lorry starts to move over. It clearly hadn't seen me (I'm seeing a trend here) and had I slowed down it would have hit me. So I sped up to pass it and it moved over behind me. I'm sure I was doing more than 30mph as we went through the camera. If I do get a fixed penalty, is it worth explaining the circumstances?

Thanks

Am I in trouble too? - GJD
Just as we approach s************ lines on the road, the lorry
starts to move over. It clearly hadn't seen me (I'm seeing
a trend here)


Honestly don't know whether you're in trouble or not PG. Sounds like you shouldn't be to me, but I don't know how these things work in reality.

About the lorries though, I think HGVs (particularly foreign ones, with the driver on the other side) have quite a big blind spot. Might be worth trying to avoid getting beside them unless you can get straight past. Should help to buck the trend.

Obviuosly that's more easily said than done in some situations. And apologies a) for not answering the question :) and b) if soneone's already suggested that.
Am I in trouble too? - GJD
Obviuosly that's more easily said than done in some situations. And
apologies a) for not answering the question :) and b) if
soneone's already suggested that.


and c) for not being able to spell properly.
Am I in trouble too? - Thommo
The politics of the scamras are getting interesting. In one of the key note speeches at the Conservative conference, it was proposed that the police be controlled locally by an elected official, also the police were castigated for going for 'soft targets' such as minor speed infractions rather than dangerous drivers.

I think we are getting in a situation with the police that we were previously in with the teachers, that is they insisted that education decisions could only be taken by education professionals and the rest of us 'laymen' should butt out. What we ended up with was a mob who implimented any fashionable idea that entered their heads and the result was a disaster.

Thus it is with the police. Leaving them to decide their own priorities has been a disaster and they are rapidly losing the support of the middle classes who were frankly the only friends they had left.
Am I in trouble too? - pdc {P}
If the camera was to the left of the road your vehicle would have been obscured from the cameras view, surely?
Am I in trouble too? - Altea Ego
PG, yes there is a trend here. You and lorries do not mix. Here is a tip. If you cant see the lorry driver in any of HIS mirrors, he cant see you. If you cant see him, back out, speed up, do whatever it takes to see him and be sure you are seen.
Am I in trouble too? - John Shelton
Lots of the opinions expressed on here about how gatsos and truvelos work are wrong. The truvelo works purely off 2 sets of wires buried under the roads surface and times you between each one. In our county any speed of 7 mph over the limit is prosecuted. The flashes used on truvelos are not infrared at all, they are merely a magenta coloured fliter fitted in front of a white light flash bulb because the home office specified that white light could not be used in forward facing shots due to it causing drivers temporary blindness. Truvelos have 2 different sets of markings . One set in front and one conventional secondary set behind, for the very simple reason that the camera can be unbolted and rotated inside the housing to face the rear. if it had the elongated set of marking you all associate with gatsos IN FRONT of the camera all the markings would be obscured by the car and so would be worthless as a secondary check on speed. Therefore 3 narrow white lines are used and the photo mUST be taken exactly on the middle of the 3 narrow white lines in frontal shots. Truvelos are acccurate to 200 mph and are normally calibrated up to 188 mph If 2 cars are shown passing the markings IE if an overtaking situation occurs the film is simply binned.no argument! Gatsos have a known fault in that they are affected by low speed high sided HGV's which causes them to flash when there is a slow or stationary qeue of traffic in front of them and a high sided HGV passes in the opossite direction, This is a well known issue and any film of this situation is also binned The secondary markings in this case are alsways checked because the film readers are aware of this fault and can actually see by the distance car wheels have travelled from one white line to the next how fast (or in this case how slow) a car is travelling.
Gatsos fault due to HGV's - buzbee
John Shelton post:

"Gatsos have a known fault in that they are affected by low speed high sided HGV's which causes them to flash when there is a slow or stationary queue of traffic in front of them and a high sided HGV passes in the opposite direction".
------
The 'slow or stationary queue of traffic in front of them' is, I assume, what has been seen/deduced by those looking at the photographs but, actually, it is not essential to have such a traffic queue for there to be a potential problem.

First the fault. I assume it refers to the speed measuring radar recording too high a speed for a departing vehicle. Second, how can this occur?

The radar illuminates the back of a departing vehicle to make use of the reflection that comes back. In the fault instance that reflection also hits the back of a 2nd vehicle that is coming the other way. Said 2nd vehicle has already passed the target vehicle and so is in a suitable position to do this and may or may not have also passed the radar. The 2nd vehicle, in turn, reflects that signal back (whence it came) in the general direction of the target vehicle such that it hits the back of the target and then is reflected back off that towards the radar. (If you don't understand this, draw it out, one radar and two vehicles).

I have described reflection as being from the back of the second vehicle but it can be from other parts. There is not the space here to go into how radar best reflects or take account of angles. It may not look like it but I am trying here to keep the example simple.

What speed will the Doppler radar measure and record in these circumstances? Answer, it depends on which of the signals is the stronger/larger as seen by the radar (the signal entering the radar). Is it the simple single bounce one back from the target vehicle to the radar, or is it the more complicated triple bounce one?

Mostly it will be the simple one but ultimately it depends on vehicle shapes, sizes, position and angles. If the triple reflection manages to become dominant, the radar will see and measure the combined speed (sum) of the two vehicles and show it as if it were the true departing vehicle Doppler signal because the folded path is increasing in length. So it will look to the radar as if the target vehicle is departing faster than it really is.

Reverse the direction of the two vehicles and you have the scene set for an approach speed measurement malfunction in a similar way.

Gatsos fault due to HGV's - Altea Ego
Any signal that is reflected (ie not a straight A-B path) will be attenuated. The stronger signal (and dont forget its a doppler shift (ie change in frequency)) that we are looking for will be the A-B path. (where A is camera and b is target vehicle)

The only time the multipathed signal (A-B-C-A) will be at a similar DB will be if the reflections (other vehicles C) are perfect 1/4 or 1/2 waves of the original radar output frequency
And as this is high the 1/4 or or 1/2 wave reflectors need to be very small.
Gatsos fault due to HGV's - John Shelton
The most common scenario we have detected is for their to be a slow or stationary queue of traffic passing the gatso and for their to be a high sided hgv or caravan passing in the opposite direction at a graeter speed. We have seen this scenario many times. although im a bit perplexed because the high sider in most of the photos ive seen is alongside the "target" car or even slightly forward of the car although it is entirely possible some of the photos ive not seen reflect (forgive the pun) the scenario you are describing. Weve also had passing cars in the opposite direction set them off when there is a stationary or slow moving qeue passing the gatso. When weve measured the "target" car we only get speeds of 10 - 12 mph (using the secondary check lines).
Gatsos fault due to HGV's - buzbee
Without seeing the actual scene I can't be more specific because it depends so much on the shapes and angles involved but I am pretty sure what I have described is the basis of the cause.

Flat surfaces are powerful reflectors of signal BUT very directional. So a flat back facing the radar but angled off, such as with a vehicle going round a bend, would be sending a much stronger signal a bit sideways than back to the radar. (some would tend to come back because the vehicle back is not just a flat sheet but has other bits/parts).

Secondly, corners are good reflectors (which is why they have them on sailing boats so the boats show up on radar). Right angle corners have the property of returning the signal on the same bearing as it entered. With your passing traffic you may effectively be forming some good reflection shapes that get enough signal back on to the flat back and then to the radar. Having a stream of traffic means more oportunities for this sort of thing.

Also a target is complex. It reflects not just a simple single microwave signal but one comprised of many signals from the various parts and each has a different phase to the other because of its distance. Thus if you put a vehicle on a turntable and look at the reflection you will get something akin to seeing the glint from a moving diamond in light. Certain angles reflect more than others. Because, with radar, the phases add up to re-inforce the signal at some angles and are cancelling (weaker signal) at others.

A signal hitting the flat side of a vehicle at an angle will tend to bounce off with equal angles of incidence and reflection so the flat sides of passing vehicles pose a bit of a problem for me in being able to show the sides account for the affect. However, if the sides are ribbed or irregular that is a different matter. As an extreme example of funnies, you can get some rare effects with suitably spaced railings. I have stood by the side of one set with a radar hand gun and measured a car coming up behind me ! The rod spacing has to be the right spacing in wavelengths for this to be possible and act as an angled reflector (railings in front on me, car behind!). Few sets will meet the requirements but it does happen and the theory can explain it.

The reason for seeing the funny effect only with large vehicles is because each reflection tends to disburse the signal (in a manner that depends on its shape) making it many times weaker (per square meter when it hits the next object) and so you are more likely to see it if you start with a large reflection. The diamond effect tends to do the rest.

No exactly the solution to your particular case, but shows how
varied things can get.

Incidently, the stealth bomber survives because the flats on the body and wings are arranged so that waves hitting it do not come back in the direction of the radar.


Gatsos fault due to HGV's - John Shelton
On the matter of truvelos which use wires in the road weve had on isolated instance of a very difficult to explain event. One site has 2 truvelo sites opposite each other with only one camera active. which means only the signal from approaching cars is detected yet on one isolated weekend we had cars on the opposite (innactive) carriageway sensors photographed ie the cars were being forced onto the active sensors driving away from them being photographed. Ive spoekn to the MD of truvelo and he tells me this is technically impossible since they only function in one direction yet we have the proof that this event has occured.
Another victim of the dreaded scamera - volvod5_dude
Recenly been sent a NIP. Had the photograhic evidence back and it is impossible to identify the driver. My wife denies it, I can\'t remember if it was me or not, it was a long journey and we frequently swop around. I feel inclined to send it back telling them to prove who was driving.

What a stupid way of trying to enforce the law.

VD5D.
Another victim of the dreaded scamera - Sooty Tailpipes
Phone up at the earliest oppurtunity and deny everything, as they know that when people get wrong tickets (due to cloned reg no.s etc....) this is exactly what they do.

Another victim of the dreaded scamera - Ben79
Whoever doesn't insure the car should accept the points, give them to your wife as being a lady, the insurance will perceive her to be a lower risk and any insurance premuim increase will be kept to a minimum :)

Oh, i'd buy some roses/chocolates/wine to soften the blow!
On my 3rd Citroen. Saxo, Xsara, C5.
Another victim of the dreaded scamera - Hugo {P}
I heard of a similar case a while back.

3 lads in a car got caught, only the three lads couldn't remember who was driving, all of them took turns as it was a long journey.

Wrote off to relevent person returning everything and heard nothing more.

Hugo
Another victim of the dreaded scamera - volvod5_dude
>>Wrote off to relevent person returning everything and heard nothing more.

Hugo

Thanks, I'll give it a go.

VD5D.
Another victim of the dreaded scamera - volvod5_dude
>>Whoever doesn't insure the car should accept the points, give them to your wife as being a lady, the insurance will perceive her to be a lower risk and any insurance premuim increase will be kept to a minimum :)<<

I think whoever takes the wrap will get 6 points or a ban( over 30mph over limit), so I don't think she will be too happy with that!

Cheers

VD5D
Speeding 'not a stigma' - pdc {P}
Frustrated drivers who smash up speed cameras are unlikely to be "shopped" by fellow motorists, a survey has suggested.

More here news.bbc.co.uk/1/hi/uk/3206538.stm
Speeding 'not a stigma' - BrianW
There are more subtle ways to disorganize the use of these things.

I have seen a couple with chewing gum in the locks: must make it difficult to get the film out !
Speeding 'not a stigma' - Dynamic Dave
I remember a frizzy haired tall fellow who presents Top Gear once suggesting that squirting expanding foam (No more gaps??) into the box works wonders as well. Not that I would endorse such an irresponsible act of vandalism you understand.
Speeding 'not a stigma' - winston
The best thing to do is to cover the lenses with a plastic disk the same colour as the lense. This way the camera will never take any pictures and the Police will think no one is speeding. Smashing them up means that they will be replaced.

I have never considered doing this by the way, just an observation!
Points are no longer an embarrassment - Dynamic Dave
British motorists are desensitised to speeding convictions because of the massive growth in the number of speed cameras, an Autocar survey can reveal.

The study, carried out by in conjunction with the RAC Foundation, revealed that one in six drivers now has points on their licence, compared to five years ago when the figure was one in 10.

www.autocarmagazine.co.uk/news_article.asp?na_id=2...4
Points are no longer an embarrassment - jeds
They are also desensitized because the huge majority who get caught know they have not put anybody in any danger whatsoever -and those that have were in stolen cars or police cars so don't get nicked anyway.

Recent figures in Avon and Somerset showed that in 9 months 419 Police officers were caught on camera exceeding the limit but only one was prosecuted.

A spokesman for the force said that the 'same laws apply to police as other road users'. God knows what colour the sky is in his world?
Safety Scamera Vans in the dark - LongDriver {P}
I passed a Scamera van on a bridge over the M6 in Cumbria at 640am the other day.

It was still very dark and so all the vehicles on the motorway had headlights on.

Can these scamera vans photograph your registration in these conditions, given the light given off by yourr headlights?
Safety Scamera Vans in the dark - Ben79
They will have infra-red or something that works in low light like some Sony camcorders do.
On my 3rd Citroen. Saxo, Xsara, C5.
Safety Scamera Vans in the dark - John Shelton
Seefive, to the best of my knowledge courts will not allow infrared images as evidence and im not aware of any cameras that are "low-light" Our truvelo cameras which are fixed are not as some suggest "infrared" they merely have a magenta filter atteched to the front of the flash unit this is home office specified for frontal photography because white light would cause temporary blindness.
Safety Scamera Vans in the dark - John Shelton
I work with fixed sites but have contact with my supervior who controls all the mobile camera in this County and to the best of my knowledge they can only operate in daylight hours, although we have imaging equipment that works in slightly depleted, but more commonly , better in conditions when it is too bright. As we can more easily dull down an image rather than add light which is quite difficult. I guess the van you saw was waiting for first light and the morning rush hour when hed get many speeders.
Safety Scamera Vans in the dark - Sooty Tailpipes
In Nottingham fixed digital systems have two cameras in each head.
These are the SPECS system, and also, what look like forward facing Gatsos with two round portholes on the front.

They have an infrared camera with infra red laights at the side/s which use the high reflectivity of the number plate to locate it within the frame and OCR system to read it, the colour image is then just tagged on as supporting evidence. I believe the London CON genstion chanrging system works this way too.

the best way around it is to make your own front number plate using proprietory parts, but use white FASCAL as the backing instead of the reflective BS AU plastic.
Safety Scamera Vans in the dark - J Bonington Jagworth
"use white FASCAL as the backing instead of the reflective BS AU plastic"

Or polish the numbers, perhaps? I saw a m/cycle no.plate recently that had chrome numbers on the normal yellow backing, and from some angles it looked perfectly normal, and from others was totally illegible! Yes, I know it's not legal...
-------------------------------
Illegitimi non carborundum!
Safety Scamera Vans in the dark - Sooty Tailpipes
I once made a front one myself, using letters I cut myself, using original black ones for a templete. I used Infra Red filter film which is a bit like the window on the front of a TV remote, but as a thin film.

I bought the a number plate from Halfords and asked the boy not to laminate it, but give me the bits in a bag.

I looked at it through an infra red monchrome video camera at work and the letters were invisible! IThe only trouble, in bright sun, the letters would shine purple, and people would comment.

I don't speed in urban areas, but hate the way this government wants a microchipped, gps tracked , camera covered big brother state, so I do what I can against it.
Safety Scamera Vans in the dark - John Shelton
Nothing works other than taking off the number plate altogather if the image is virtually unreadable we send it for special enhansement in the labs and any different material used for letters will show up no matter what it is made of or how highly polished it is the only way to escape is for the numbers to be made of exactly the same stuff be it colour etc as the backing, but then in essence you would have a blank plate, just coloured! all we do is rely on the different reflectivity of different material / colours used.
Safety Scamera Vans in the dark - No Do$h
So a hi-power flashgun operating from a slave-unit (triggered by the flash on the Gatso) and firing back towards said cyclops no good either?

There goes that get rich quick scheme. Perhaps I should spend my time inventing a better scamera if I want to be wading in money.
Safety Scamera Vans in the dark - smokie
Yu also need to be first with the idea - see this, from 1999!!

news.bbc.co.uk/1/hi/uk/479483.stm
Safety Scamera Vans in the dark - No Do$h
So a better camera it is then.
 

Value my car