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..because everyone slows down for them but I've only met people who've been done by gatsos. Are they....EVEN ON???
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400 odd people reportedly got done in four days when they had them on the M275 a couple of years ago. Despite leaving warning signs up for weeks before and a huge PR campaign by Hants police!
Colleague got done on the M62 when they had them near Leeds. Had to explain to him in very simple terms how distance equals speed over time. Muppet was just slowing down at the cameras!
MrsT got done in Southport, she did the "correction" course rather than taking points. On the course there was a guy from Wales who had been caught for the third time 🙄
I'm sure the ones currently installed on the Glasgow road works will be raking it in given some of the madness I witnessed recently.
The M6 Carlisle works made a nob or two;
http://www.****/news/article-1256738/Speed-camera-trap-M6-racing-record-3m-haul-fines.html
A bit of googling answers your question;
http://www.manchestereveningnews.co.uk/news/greater-manchester-news/m6-speed-camera-dishes-out-8811348
Don't all speed cameras measure 'average' ? It's just the distance / time over which that average is measured which varies.
True i suppose, Marcus!
Yes l loads of overripe do show down for the cameras. I always wonder of they think that average is the average of the speed they go through each camera at..?
Especially annoying on the a9 where loads of cars slow down to 50...
Muppet was just slowing down at the cameras!
Despite having these on a 5 mile stretch of my local DCW for about 10 years, it's amazing how many people you see still doing this!
Disappointed, expected thread to be about members basking in the glory of being caught on camera exceeding permitted road speeds on their bikes. 😉
Don't all speed cameras measure 'average' ? It's just the distance / time over which that average is measured which varies.
LOL. Impressive level of pedantry there. I think the policeman-holding-gun type is instantaneous speed though.
Load of mouth breathers from my home town crying about being caught in the new bit of managed motorway on the m1 despite the 10 foot by 15 warning signs . No one is going to be dumb enough to own up to being so incapable of controlling their car that they get caught by a set of average cameras even if you are not paying attention and speed through one you have ages to reduce your average speed to below the limit.
I was done twice on the stretch between Stocksbridge and J36 M1, twice in ten days, the NIPS were 3 weeks apart so didn't hear about the 2nd until I returned home after a week overseas, so 6 points for 3 full years, when there is a good chance you could easily lose your job it tends to focus the mind a bit better, the fuel saving and therefore my mileage claims improved though.
THINK ON !!!!!!!!!!!! 😉
Don't all speed cameras measure 'average' ? It's just the distance / time over which that average is measured which varies.
It measures your speed at the point you pass the camera
Not sure why you want to claim one measure at one point is an average
Can you explain the pedantry to me please?
He means that a tradition speed camera takes two pictures. The speed is found by dividing the distance traveled by the car in the two photos by the time between the two photos. So he's correct, this is also an average.
On a similar note, I've often wondered how you can be prosecuted for exceeding 50 miles per hour, when you haven't travelled 50 miles or travelled for an hour ? Surely a speed limit of metres per second would be more appropriate
As is the hand held one I think - measures how far away you are, measures it again a set time later, works out the distance you've covered in that time. So applying he same logic that's average speed too. Average speed over about 2-3 seconds I suppose (that's how long [s]they take[/s] the old ones took to get a reading.
On a similar note, I've often wondered how you can be prosecuted for exceeding 50 miles per hour, when you haven't travelled 50 miles or travelled for an hour ? Surely a speed limit of metres per second would be more appropriate
Good morning Mr Taylforth.
Don't some hand held ones work by doppler shift?
Possibly because it's 22.352metres per second....
Is that radar? I think there are some radar ones still on the go but it's mostly laser ones as they are, well, much better all round as I understand it.
Don't some hand held ones work by doppler shift?
That's basically how RADAR works, but it's old tech as far as speed cameras go. I'd be surprised if it's still in use (in the UK at any rate).
Do the M25 ones work?
When the overhead gantry speed signs show 60 for instance you still see folks rattling along at least 20-30-40 plus mph over that...
I do wonder if anyone knows how/why these things work.
When the M1 in Derbyshire had an average 50 limit for the roadwork between junction 28 and 31 they caught around 100 drivers a day over the two years or so it was in operation. According to our local paper one guy got done three times!
By my pig-physics reckoning, you can't measure speed instantaneously since v = d/t. If t=0 then v can only be infinite (or 0 I guess).
I might be pedantic, but IANAPhysicist. 🙂
I was done twice on the stretch between Stocksbridge and J36 M1, twice in ten days, the NIPS were 3 weeks apart so didn't hear about the 2nd until I returned home after a week overseas, so 6 points for 3 full years, when there is a good chance you could easily lose your job it tends to focus the mind a bit better, the fuel saving and therefore my mileage claims improved though.THINK ON !!!!!!!!!!!!
Are you sure it was the average cameras?
They Park the scamera van on the bridge also with its side window pointing down the bypass
Basically you could have done 20 mph all the way along there but just as your overtaking at 67mph up the hill BANG they nail you between the avg cameras
crafty buggers
I see your 'logic' but you can have velocity at a particular point in time. If you don't, then you also have no kinetic energy (since KE = 1/2 mv^2) and if you have no KE then where's it gone / you'll have to rewrite general relativity. And that's too difficult for a Monday morning.
richmars - MemberDon't some hand held ones work by Doppler shift?
Used to, but it is not an instantaneous speed measurement.
Speed = distance/time, you have to have both to work it out so all speed measurement is an average.
Aren't velocity and speed different things ?
Aren't velocity and speed different things ?
Velocity is a vector ie has direction whereas speed doesn't.
the cameras on the M4 and M5 on the approaches to the Almondsbury Interchange are have been used more than 5,000 times to catch drivers exceeding the 70mph limit in the past seven months, leading to fines totalling more than £500,000 being issued.
I see your 'logic' but you can have velocity at a particular point in time. If you don't, then you also have no kinetic energy (since KE = 1/2 mv^2) and if you have no KE then where's it gone / you'll have to rewrite general relativity
You can state a velocity at an instantaneous point in time, but the only way you'll know what that velocity is, is by measuring over time, either side of that point.
The instantaneous point in time doesn't exist, so KE and relativity laws are safe.
you'll have to rewrite general relativity. And that's too difficult for a Monday morning
Give me enough coffee and a place to stand and I will move the universe!
Velocity is a vector ie has direction whereas speed doesn't.
You've seen my mum drive too?
I too had a colleague that was convinced average speed meant they took your 'instantaneous' speeds at all the cameras, added them up and divided by the number of cameras to give his average of all.
The fact he never got ticketed was mainly because other traffic moving at 50-odd slowed him down sufficiently that his constant speed up / slow down style never got his average sufficiently high (they must have quite a degree of leeway)
But unfortunately, he also saw the fact that he didn't get ticketed as validation that his opinion was right 🙄
a similar note, I've often wondered how you can be prosecuted for exceeding 50 miles per hour, when you haven't travelled 50 miles or travelled for an hour ? Surely a speed limit of metres per second would be more appropriate
I like your thinking!
Do you send a bill to your bank when you get money out from one of those 'Free Cash Machines' and the money gets taken from your account?
Do the M25 ones work?When the overhead gantry speed signs show 60 for instance you still see folks rattling along at least 20-30-40 plus mph over that...
I do wonder if anyone knows how/why these things work.
Not every gantry has a camera, you can see which ones do from quite a long way back.
They've just replaced a couple of GATSOs on the A316 with average cameras over the whole bit (well from the end of the M3 up to Richmond). Fairly sure that will result in a bit in the local newspaper shortly...
For anyone that does the M4 managed section around Bristol occasionally, there are a couple (1 each direction) of speed cameras which are pinned to the LHS of the gantry support. I'm fairly sure these are also linked to the mandatory speed limits which are imposed during congestion, but also they'll flash when no speed-limit is indicated on overheads. I may have seen some overhead ones flashing but I've seen those two pinging lots of people. Had a 4 week-ish period where I was doing that section from M5 to M32 every morning/evening and there was hardly a day I didn't see both of them flashing drivers.
surely if you obey the speed limit these cameras are not an issue? 😕
ah, Mr Killington. We've been expecting you.
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You have to be careful with the laser ones; especially if you have a blue car…
The laser also works essentially using the doppler effect - a laser is sent out at a know frequency and it bounces back off the bonnet of a moving vehicle. Because the “effective” frequency of the reflection received is higher by a known amount, the speed of the vehicle can be calculated.
Now, the trouble is; if you are driving a blue car, blue light is a higher frequency than red light and it has the effect of changing the reflected laser light that little bit more than a red car does and means you can be measured doing a higher speed than you actually are.
That’s why they have to have some leeway in the system.
They don’t tell you these things, do they??? 😉
Rachel
if you divide zero by zero you don't get infinity (or zero). Ask Siri if you don't believe me!By my pig-physics reckoning, you can't measure speed instantaneously since v = d/t. If t=0 then v can only be infinite (or 0 I guess).
Given the level of pedantry being displayed, quite surprised no-one picked up on this gem! 🙂Had to explain to him in very simple terms how distance equals speed over time.
little bit more
I demand numbers!
Stoner - difference between a fixed penalty and a conviction, probably… 😀
Rachel
All this talk of the laws of physics is confusing me at the moment, though - my new motorbike, an S1000XR accelerates so fast I’m beginning to doubt these “laws” are as reliable as we think they are...
[quote=allthegear ]You have to be careful with the laser ones; especially if you have a blue car…
The laser also works essentially using the doppler effect - a laser is sent out at a know frequency and it bounces back off the bonnet of a moving vehicle. Because the “effective” frequency of the reflection received is higher by a known amount, the speed of the vehicle can be calculated.
Now, the trouble is; if you are driving a blue car, blue light is a higher frequency than red light and it has the effect of changing the reflected laser light that little bit more than a red car does and means you can be measured doing a higher speed than you actually are.
That’s why they have to have some leeway in the system.
They don’t tell you these things, do they???
Rachel
surely the laser is just a carrier for the signal?
surely the laser is just a carrier for the signal?
Only if it is being fired by a postman.
Rachel
The bit I don't get is what constitutes a separate offence/instance of speeding. If they set up 4 of the non-average cameras along a short stretch of road presumably you could lose your license straight away if you got done by all of them. But if they were average speed cameras it would only be one offence.
On a similar note, I've often wondered how you can be prosecuted for exceeding 50 miles per hour, when you haven't travelled 50 miles or travelled for an hour ? Surely a speed limit of metres per second would be more appropriate
Because you are travelling at a RATE of 50mph. No judge or jury would side with your argument.
SImilar to the fact that ALL laser devices have not been type approved for use on motorcycles yet they are....
The smaller front area and lack of sufficiently large reflective areas causes real issues for a correct reading.
Causes issues on my garage door opener too - sets it off and makes all sorts of noises... 
If you spread jam on your bonnet it will absorb the laser beam, marmalade may also work.
IMO, the best thing about the ambiguity (as demonstrated by all these threads) of average speed cameras through roadworks is that because very few drivers are absolutely sure how they work, if they're switched on, etc, that the great majority slow down to the indicated limit and traffic flows at much higher densities than when they used gatsos.
My brother has just been done on the one on the M5 jcts 6-4. FYI.
Jam doesn't work due to the build up of wasps.
it dosent work by Doppler, it's timed (so an average again for the pedants). Funny post though, might have to spread thatsurely the laser is just a carrier for the signal?
Heisenberg got stopped by the police, who asked him how fast he had been going.
"No.", he said, "But I know exactly where I was".
They don’t tell you these things, do they???
Can you jam* the signal
* not that kind of jam
Can you jam* the signal* not that kind of jam
<whispers> - when was the last time you saw a pink car getting a speeding ticket?
I didn’t tell you this…
Rachel
And this is before we start the discussion about in fact being stationary and allowing the world to rotate beneath us at several thousand mph
Now, the trouble is; if you are driving a blue car, blue light is a higher frequency than red light and it has the effect of changing the reflected laser light that little bit more than a red car does and means you can be measured doing a higher speed than you actually are.That’s why they have to have some leeway in the system.
They don’t tell you these things, do they???
Because it's wrong.
A laser beam is an exact single frequency of light, and it's a single wave rather than the confused mess you get from a filament lamp that's why it's used, you can count the number of waves as a very accurate 'clock' between the light being emitted and returned. 2x pulses give your 2x distances and a a time and therefore speed.
They're not dopler effect. That only works (at car/plane speeds) with Radar.
As the laser is a single frequency of light it won't be absorbed by the car's paint unless it happens to be exactly the right color for the laser, in which case it'll absorb it completely, a bit like radar absorbing paint, to the radar/laser it would just appear 'black', it won't change the frequency.
Even cameras with lines on the road are measuring and instantaneous (to all intents) speed, they measure it as you pass the camera, then the 2 flashes are just photographic evidence, the speed recorded is the one measured by the laser/radar.
Hilariously, they make naff all sense on the M3 when you spend 30 minutes crawling at 15 mph or less. I'm not sure what the maths is but I wonder what speed you could drive at to average 50mph by the time you get to the M25.
Juamann absorber...its the only way to maybe possibly be sure
Though paradoxically a delorean may also negate receiving a ticket
or stealth
have you noticed how they generally aren't being removed once the roadworks have finished.
how long before a national network of speed averaging cameras...
thisisnotaspoon - Because it's wrong.
You mean everything I said was wrong? Oh no - how could that be? I’m so embarrassed…
🙄
Rachel
We've got some road widening controlled by some average speed cameras.
The poor Merc driver beside me yesterday got his calculations badly wrong when he forgot he wasn't at the last set of cameras, but the second last when he gunned it. I don't think slamming on the brakes right beside the last set was going to make much difference to his rather large average speed...
The bit I don't get is what constitutes a separate offence/instance of speeding. If they set up 4 of the non-average cameras along a short stretch of road presumably you could lose your license straight away if you got done by all of them. But if they were average speed cameras it would only be one offence.
To get done more than once, I think there has to be some evidence that you slowed down to below the limit between each instance of getting caught over it, otherwise the argument is that it is one continuous offence. Things such as going in the opposite direction, stopping at services, going through a town, that sort of thing. I can't recall any case law but I think that's right.
I heard the following last week, which I find hard to believe. The story went 'of the avg speed cameras on the A9, only three pairs are working at any time. You can get a SatNav which tells you whether you're at one, and you can ignore the others.'
I'm guessing they are only cameras, maybe with IR lighting at night for clarity, logging number plates* and it sounds like BS. Can anyone confirm?
They seem to work, lots of cars at the same speed and well spread out. It remains obvious that lots of drivers don't know how to overtake except on the dual sections.
*Didn't the Gov buy the technology from TrafficMaster yonks ago?
The poor Merc driver beside me yesterday got his calculations badly wrong when he forgot he wasn't at the last set of cameras, but the second last when he gunned it. I don't think slamming on the brakes right beside the last set was going to make much difference to his rather large average speed...
depends how many cameras! if he went through 9 cameras at 50mph, and then one final stretch at 80mph, he'd still only have averaged 53mph across the whole thing*.
if there were only 4 sets of cameras though, he's probably jiggered 😉
*if the cameras were equally spaced etc etc
OP, we had a thread before and yes STWers have been done
Foreign plates anyone ?
gosh, quite a response (couldn't find the previous thread)
Loving the physics chat, do let us know when you have revolved the idea of an instantaneous speed
IMO, the best thing about the ambiguity (as demonstrated by all these threads) of average speed cameras through roadworks is that because very few drivers are absolutely sure how they work, if they're switched on, etc, that the great majority slow down to the indicated limit and traffic flows at much higher densities than when they used gatsos.
I agree, they do work and that's because we are all scared. There is no flash, so no feedback, so we err on the side of caution. I can see some people here have been done...but the question remains: how fast could you go through them? If you took the racing line (which is legal) and they give you a bit of speedo error could you go through at 60 in a 50 I wonders?
I was told years ago by people living there that this is one of the reasons why motorists in France had a habit of picnicking by the side of the road. If you stop for half an hour on the road you can then drive as fast as you want as you'll never make it back up to the average speed.Hilariously, they make naff all sense on the M3 when you spend 30 minutes crawling at 15 mph or less. I'm not sure what the maths is but I wonder what speed you could drive at to average 50mph by the time you get to the M25.
how fast could you go through them?
I always put the cruise at 55mph, and I always get overtaken.
if he went through 9 cameras at 50mph, and then one final stretch at 80mph, he'd still only have averaged 53mph across the whole thing*.
You do realise that's not how it works, right? It's an average between two successive cameras, not across all of them.
how fast could you go through them? If you took the racing line (which is legal) and they give you a bit of speedo error could you go through at 60 in a 50 I wonders?
You can go through a SPECS camera as fast as you like. They don't measure the speed of passing traffic, they just know how long it's been since you passed through the last one.
You do realise that's not how it works, right? It's an average between two successive cameras, not across all of them.
😳
nope, didn't know. although now i come to think of it, there'd be no point in having any interim cameras if it was just treated as one single block...
You'd still need repeaters next to entry / exit lanes, but yes.
[quote=Cougar said]
You do realise that's not how it works, right? It's an average between two successive cameras, not across all of them.
Not necessarily successive cameras! The system operates with camera pairs, entry and exit which might be grouped with overlap.
The system design is such that the cameras can only operate in pairs, each pair can only monitor one lane of a multi lane road.[7] It is therefore, at least in theory, possible to escape detection by changing lanes between the entry and exit cameras since the exit will be captured by the exit camera of a different pair.[7] However, in reality, the authorities are able to easily defeat this tactic by arranging for two or more sets of pairs of cameras to have overlapping areas of monitoring.[7] Since the driver cannot tell which cameras are 'entry' and which are 'exit', as they look identical, they cannot tell where to change lane to escape detection.
I didn't know that, but it makes sense (I did know about the lane thing though).
Since the driver cannot tell which cameras are 'entry' and which are 'exit', as they look identical, they cannot tell where to change lane to escape detection.
what about the hard shoulder. if i swerve violently onto the hard shoulder every time i see an average speed camera array, will they pick me up then?
[quote=theotherjonv said]will they pick me up then?
I imagine someone will Jon 😉
I was told years ago by people living there that this is one of the reasons why motorists in France had a habit of picnicking by the side of the road. If you stop for half an hour on the road you can then drive as fast as you want as you'll never make it back up to the average speed.
They don't have average speed cameras on French roads, just hundreds of the standard radar ones. The rumour of timing on the peage is I think nonsense as the toll booths are so far apart apart - often more than 200km
On a quantum level could you argue that you were both there and not there at the same time, as a defence to your speeding?