How you average speed cameras work?

[chriswt]

I'm guessing that the yellow CCTV style cameras take a picture of your car/VRM and then the next set of cameras further down the road take another pic and the average speed is worked out!?!?!

However, during rush hour thats a heck of alot of cars to monitor.

I've also seen several "clever" people slow down for the camera and then speed up until the next cameras!

 

[w124coupe]

We had a demo of the SPECS (blue ones on the "batman" poles that look like little gattling guns).

They can take digital pics fast enough to get all cars nose to tail at 120MPH and then the controller uses pattern recognition to pick out the number plates.

Each plate is added to the database with the the time and then the "paired" unit down the road (up to 1 mile) looks up each plate as it captures it.

Quick maths to work out distance/time = MPH and, if over the trigger, a digital file, with the pics, goes to the civilian centre where the NIPs are prepared.

All sorts of urban myths about lane changes etc are all B.S. - all catered for in the software.

 

[chriswt]

Thought it must have working like that as I couldn't see another way of it working. Amazing how much time you have on your hands when driving at 40mph through roadworks!!!

I'm only talking about the roadwork average speed cameras (yellow on blue poles) and in that case if you were to drive really really close to the back of a lorry at 40mph the camera surely can't get your plate (stupid idea which I would never do!!).

I guess the drivers who slow down for the cameras and then speed up again really should have paid attention to 'Mode, Mean and Median' at school.

 

[BTB 500]

Easily fooled though with the "doctored" plates (silly fonts, bolt heads, etc.) you see all the time. Not sure whether altered spacing alone is a problem for ANR software?

 

[Spinal]

Easily fooled though with the "doctored" plates (silly fonts, bolt heads, etc.) you see all the time. Not sure whether altered spacing alone is a problem for ANR software?

From what I know, pictures of plates that are not "recognised" are flagged to the (human) controller, which can then take it onto himself to recognise it and send out the NIP for speeding (possibly along with one for an illegal plate?)

Michele

 

[BTB 500]

From what I know, pictures of plates that are not "recognised" are flagged to the (human) controller, which can then take it onto himself to recognise it and send out the NIP for speeding (possibly along with one for an illegal plate?)

Michele

For Gatso-type cameras, yes. But we're talking about SPECS-type ... which have to process every single plate that goes past. If they can't recognise a plate then they can't work out the average speed from A to B, so there's no offence!

 

[w124coupe]

Spinal is right - in fact "big brother" goes one step further...

Plates with a recognition error ALL go to the human reading centre and from there on to possible prosecution for number plate offences.

Worse still, if you use "flash" plates or the various sprays available, the guidance now is to prosecute for attempting to pervert the course of justice (they don't work anyway as the operator just "inverts" the image or tweaks the contrast and the plate is easily readable).

AND, if a mobile laser video unit fails to get a speed fix on your car, the reg is added to a database of failed readings. If you then get another hit the same way, a mobile unit is sent to the registered keepers address to check for a laser jammer - there is a test case running on this right now - again, the offence is attempting to pervert the course of justice (it may be reduced by the judge to obstructing a police officer in the course of his duty).

At least we are not as bad as the USA and Australia - they both have police cars with radar units that are approved to catch you coming TOWARDS the oncoming police car, again, equipped with video so they don't even need to stop you....would be a nightmare on the M40.

 

[Swiss Toni]

Spinal is right - in fact "big brother" goes one step further...

AND, if a mobile laser video unit fails to get a speed fix on your car, the reg is added to a database of failed readings. If you then get another hit the same way, a mobile unit is sent to the registered keepers address to check for a laser jammer - there is a test case running on this right now - again, the offence is attempting to pervert the course of justice (it may be reduced by the judge to obstructing a police officer in the course of his duty).

Out of interest, what legal power would the mobile unit have to check for a laser jammer? and who keeps the database? is it national or just local? and is there any offence of having a jammer fitted (and if not, where does the proof that it was "in use" come from?).

Cheers

 

[BTB 500]

Plates with a recognition error ALL go to the human reading centre and from there on to possible prosecution for number plate offences.

Worse still, if you use "flash" plates or the various sprays available, the guidance now is to prosecute for attempting to pervert the course of justice (they don't work anyway as the operator just "inverts" the image or tweaks the contrast and the plate is easily readable).

Pretty sure the SPECS cameras we're discussing don't use flash.

I wonder what the success rate is for ANPR? With moving targets, reflections, shadows, foreign plates, etc. let's guess at 95% overall (which would be pretty good). On that basis if a car passed (say) every 2 seconds there'd be over 2,000 recognition errors a day to be investigated from that camera alone! So IMO they'd only ever be able to do random spot checks and follow-ups.

Pretty sure that's why I see so many people getting away with altered plates in central London, where the congestion charge cameras use the same technology.

 

[Shude]

For Gatso-type cameras, yes. But we're talking about SPECS-type ... which have to process every single plate that goes past. If they can't recognise a plate then they can't work out the average speed from A to B, so there's no offence!

It's not really plate recognition though, the first part is pattern recognition (as stated by w124coupe) It just has to look for the same pattern at the next camera, unless you change plates between cameras (now there's an idea!) you'd still be caught.

Maybe rotating plates, self-destructing detachable plates or perhaps plates with dynamic characters would work here!

 

[Ryan S]

These cameras were in operation between Dundee and Perth at the weekend.
Almost everyone slowed down to bang on 40mph apart from the motorbikes.

 

[BTB 500]

It's not really plate recognition though, the first part is pattern recognition (as stated by w124coupe) It just has to look for the same pattern at the next camera

Maybe. I assumed though that the system did pattern-to-text conversion ... then matched text from one camera to text from the next. I'd have thought that matching pattern to pattern would be pretty complex, with an infinite number of possibilities!

I'd be interested to know how it does work, I did a few searches earlier but couldn't find any details.

 

[Shude]

Maybe. I assumed though that the system did pattern-to-text conversion ... then matched text from one camera to text from the next. I'd have thought that matching pattern to pattern would be pretty complex, with an infinite number of possibilities!

I'd be interested to know how it does work, I did a few searches earlier but couldn't find any details.

Ok then, let's assume it looks at a plate and gets it wrong when OCRing, it would probably get it wrong every time wouldn't it? So that leaves it completely open to abuse, which is probably what's happening 2000 times daily for each camera

 

[Dieter]

Hi,

Click here for a PowerPoint demonstration of how Specs works:

http://www.speedcheck.co.uk/

then click on "Download SPECS Presentation" at bottom of page.

Cheers,

 

[Dieselman]

Nottingham was the first place to install specs cameras about 10-12 years ago, initially on a particular stretch of the ring road. They are now everywhere, even on the A46 in rural parts.
EVERYONE now drives at the speed limit as these cameras are so good. Only a fool slows down for the camera and then speeds up to the next one.

iirc road sensors detect the vehicle speed as it passes each camera. Pass one camera too fast and you're Ok, pass two and you're nicked even if the average speed was below the limit.

This is where cruise control and limiter are really useful.

Can't APNR cover something like 240,000 plates per hour? That's 4000 per minute.

 

[w124coupe]

Re the questions, this is what we were told (the demo was by the local plod who has a "community relations" role - he also has a curly tail ).

The specs is pattern recognition, there is still a drone employed to copy type the reg into the NIP document using the close-up and distance photos....the specs uses infra red illuminitation (thats what the "tubes" around the edge are).

They like SPECS as it leads to stable,low speeds in roadworks etc which leads to shorter queues apparently (no "red wave" effect caused by jamming on the anchors).

Big push on doctored plates, using the same systems in place to stop cloning (the regional forces swap info to make a sort-of national system).

Bolts, spacing, fonts etc are all offences and can result in fines or loss of the right to use the (private) plate.

He mentioned (and showed pics of) 3 plates locally that they had taken action over. One has used 3 bolts to make a C into a G (seen as a "big" offence as it attempts to change the identity of the car), the others were spaced wrong to make names (seen as a nuisance and cautioned and threatened with report to DVLA/poss loss of right to use plate).

Laser jammers are illegal to use in the UK and the info earlier re failed Lidar reads is correct (i.e. plod targets your car and fails to get a "lock" over several trigger presses as you approach) - if it happens on 2 separate occasions for the same reg, expect a visit with police vehicle inspectors who will check your car over.

 

[BTB 500]

If SPECS uses pattern matching to pair up 'entry' and 'exit' times for a vehicle then at that stage it can't spot an altered or unreadable plate (a pattern is a pattern). I thought SPECS automatically sent NIP's? In which case it must then convert pattern to text in order to look up the owner from the reg. no., and that would presumably be the stage at which an 'unreadable' plate would be flagged to a human operator (who would interpret the still images to try and get a reg. no.).

That's fine, but not what I thought was being suggested earlier i.e. that the system would flag ALL dodgy plates (whether you were speeding or not).

 

[w124coupe]

I can only say what we were told and shown.

The specs controller that runs the pair of cameras creates a database of patterns that match AND where the speed was over the trigger, according to both of the timing circuits in the system. It looks for a plate within the shape of a car and then matches the plate - no OCR as far as I know.

The database is then processed by a civilian who looks at the pics (black and white plate close up from both entry and exit cameras plus a colour shot of the whole car) and copy types the reg into the NIP doc. I think the plod said OCR for the plates is in the future for SPECS.

The application has buttons to change the contrast and to invert the image, both to help make out numbers on dirty or altered plates.

The civilian also has the option to refer the plate on to another department if the DVLA look-up for the car lists a different model or colour to what's on the screen or if the plate is illegal in any way.

The NIP data is also linked in to the stolen cars list.

 

[w124coupe]

One thing he also did say was that there is a push to nab people who get others to take the points for them - the video and stills from the enforcement "partnership" vans gives a pretty good view of the driver.

They are starting to look closely at any returned NIP forms blaming another driver where the main driver is on 9 points.

If caught, they will prosecute both driver and the fall-guy for perverting the course of justice - a criminal rather than motoring offence which carries up to 5 years jail!

I did ask how long the photos/videos were kept but he claimed not to know...

 

[agatward]

Pattern matching is very trivial (especially in modern FPGA or ASIC silicon) and using wavelet data compression techniques it is possible to compress the entire number plate pattern in greyscale into a few kbytes.

Combine this with up-coming neural net research which could potentially learn that "for this shape car, the number plate is roughly here" you could cut down 90% of search times to in the nanosecond range.

Of course all this requires data storage, but both high-speed data networks and storage are cheap now even compared to a year ago.

As for the OCR, this is much better nowadays than people realise. Again neural nets could be trained to recognise characters in the "standard" typeface, leaving just the modded ones to be handled as special cases.

Certainly computer vision research in the university I work at already allows real-time tracking of people within crowds at tube stations based entirely on CCTV footage (and we all know how crap the older CCTV cameras are for image quality). Imagine this type of processing power being applied to recognising number plates.

Also bear in mind that you're not really limited by the rate at which the camera sensors can capture information any more. The newer, stock CMOS camera ICs available from the likes of Omnivision allow you to capture at up to 120 frames per second. Specialist camera systems that I have seen recently allow the capture of VGA resolution (640 x 480) at up to 1068 frames per second. The real bottleneck here is how fast and reliably you can process the data.