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  • FIRST POST
    • AsaBlade
    • By AsaBlade 5th Sep 17, 3:43 PM
    • 12Posts
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    AsaBlade
    Mobile Camera Speeding Offence "Rolling Footage"
    • #1
    • 5th Sep 17, 3:43 PM
    Mobile Camera Speeding Offence "Rolling Footage" 5th Sep 17 at 3:43 PM
    Hi all.

    Any advice is most welcome.

    I have today received a Notice of Intended Prosecution for an alleged speeding offence of travelling at 36mph in a 30mph zone.

    I have reviewed the photographic evidence provided it suggests that I was doing 29mph at the time of the alleged offence. I also have tracking information on the vehicle which suggests that I was doing 29mph too (and certainly at no point did I exceed 30mph).

    I decided to contact the Camera Partnership to confirm the time lapse between the two photos that they provided me with in order to decide whether to challenge the case in court. However, the representative at the Camera Partnership informed me that the evidence wasn't obtained through time lapse shots (as a Gatso camera would at 0.5s or 0.7s intervals), but rather, they said the evidence was of "rolling footage". They went on to say that the rolling footage shows me doing 36mph and then slowing to around 21mph as I passed the speed van.

    My questions are:

    1. Has anyone had any encounters with these types of speed cameras - that use rolling footage rather than time lapse shots?

    2. How do they work to calculate your speed from ONE frame (as was suggested)?

    3. Are they reliable?

    4. Has anyone successfully appealed a NIP that used this type of camera?

    I wouldn't usually go to these lengths to challenge something like this (although this is my 1st alleged speeding offence after 21 years of driving in excess of 40,000 miles a year) but I remember the day as clearly as it were yesterday. I actually had my vehicle on cruise control set at 30mph around 500 yards or so prior to the van being sighted (or the van being able to spot me). I then cancelled the cruise control as I approached the van as traffic was slowing in front of me (hence the speed registering around 21mph as I passed the van).

    Now if I was speeding then hands up - I accept my punishment and take it on the chin. However, my recollection of the event, coupled with the tracking data (which shows me doing 42mph in a 40mph zone a few miles prior and highlights this on my print out) and with the photographic evidence they have supplied makes me really want to challenge the NIP but I'm unsure as to how these types of cameras work.

    I just don't see how it could have registered 36mph when I was set on CC at 30mph.

    NB - The road is dead flat - no chance of vehicle runaway while on CC.

    Any help is greatly appreciated.

    AD.
Page 3
    • Manxman in exile
    • By Manxman in exile 6th Sep 17, 10:50 AM
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    Manxman in exile
    To add, OP, see what the Safety Partnership send - I'll be pleasantly surprised if what they send is what they intend to rely on in court. Review what they send first, but your best chance of fighting this without cost to yourself might be to show them what you have and see if they cave in. They may decide not to proceed, they may just say see you in court. There is also a risk they could withdraw SAC and fixed penalty offers and just say see you in court if you handle this in a bull in a china shop way.

    I would supply it in a way that says you're curious that they have found you speeding but your dash cam thinks otherwise.

    The difficulty is that their equipment is calibrated, yours isn't. And by calibrated, I mean accepted legally as such. You can change settings on your dashcam to change the date for example - mine came with a defaukt date and time.

    Choose your battles. This one isn't unwinnable, but if winning leaves you out of pocket, is it worth the fight? That's up to you, but there are quite a few stories on Pepipoo where people have turned down an SAC and ended up much much worse off.
    Originally posted by Mercdriver

    I think this is sensible advice. If you are so confident about your evidence, try to share it with them in the way suggested. If your evidence is persuasive and conclusive they may drop it to avoid embarrassment in court. But I'd have to say, I think it's more likely that you are mistaken in some way and that you actually were speeding.


    I'd second the advice of mercdriver and other posters to post over on Pepipoo. I've read many speeding posts on there and I don't think I can recall one where somebody has successfully challenged one of these devices in court. And if the prosecution bring in expert witnesses to support the technology, I understand you could be talking about four figures in costs (not including your own costs).


    I'm not sure whether understanding the technology helps you. Presumably you've been pinged by a laser device at a range of up to 1000m (I know you say 500m, but are you sure?) and it has calculated your speed virtually instantaneously. The court will presume the device is accurate. Can you cast reasonable doubt on that? Will your uncalibrated dashcam footage be enough to do so? How can you prove its accuracy?


    If you really want to understand the technology get over to Pepipoo where you can discuss things like "cosine slippage" (I think).


    I'd get over to Pepipoo anyway, if I were you.
    • Warwick Hunt
    • By Warwick Hunt 6th Sep 17, 10:51 AM
    • 244 Posts
    • 119 Thanks
    Warwick Hunt
    IF the SCP send you the video of the incident AND it shows the cross-hairs AND this shows the target varying THEN you might have a chance of challenging it and winning. *

    If not then take the SAC and be done with it. No points and minimal hassle. Fair? No, but it's the pragmatic approach.

    * I recall a fairly recent media article or forum thread where someone was accused of speeding but was able to prove human error on the part of the camera operator. I can't find it right now though.
    Originally posted by DoaM
    But he needs to be reminded that to get the footage, he needs to turn down the course, reject any fixed penalty notice, be charged to court and enter a not guilty plea.
    • facade
    • By facade 6th Sep 17, 11:23 AM
    • 2,838 Posts
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    facade
    What the OP originally wanted to know was how the laser speed gun works.

    The gun sends a very short pulse of infra red light straight out the front. It reflects back off a flat surface straight back to the gun.
    It measures the time for the pulse to go there & back, and works out the target distance.
    It does this around 1000 times a second, so it can deduce the speed of the target by the rate of change of distance, over about 1/3 of a second, which gives very good accuracy.

    The cone of light is very small, and unlikely to be coming off another vehicle, the evidential footage will show where the beam was aimed and whether or not a speeding hawk dived through the beam, or if the beam flicked from car to car.

    The cosine slippage Manxman in Exile refers to is caused by the car moving at an angle to the beam. This works in the car's favour as the distance is measured to the gun, so the greater the angle between the beam and the direction of the car the less the distance to the gun reduces. (If the car travels at 90 degrees to the beam, it wont ever get any closer to the gun, and the measured speed would be zero)

    I don't know how the OP's cruise control works, but all the ones I've had will allow you to overspeed on a downhill, as they didn't use the brakes: the cameras are sighted at the bottom of hills as cars accelerate down them unless the driver is using the brakes. So it is possible that the OP was caught at a momentary overspeed that beat the cruise control, due to the spot-on placement of the camera.


    Bottom line is try over at pepipoo.

    The idea of confusedly asking them to review their footage, as you are sure you were below 30 due to cruise control is a good one, as if they have made a mistake they would surely drop the charge.

    However, speeding is an absolute offence: you either were travelling at greater than 30.0000000000000000 mph or you weren't (there is no question of intent). Forget any defence about your inaccurate speedo or faulty cruise control.
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science )
    • brianposter
    • By brianposter 6th Sep 17, 10:14 PM
    • 143 Posts
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    brianposter
    What seems to be missing from the comments is an appreciation that two independent pieces of evidence should normally trump any single piece of evidence, however well calibrated the single piece of evidence may be.
    Infallible systems have so often proved to be flawed that there really should be no argument.
    Last edited by brianposter; 06-09-2017 at 10:20 PM.
    • Car 54
    • By Car 54 6th Sep 17, 10:51 PM
    • 2,237 Posts
    • 1,436 Thanks
    Car 54
    What seems to be missing from the comments is an appreciation that two independent pieces of evidence should normally trump any single piece of evidence, however well calibrated the single piece of evidence may be.
    Infallible systems have so often proved to be flawed that there really should be no argument.
    Originally posted by brianposter
    Can you point to any source for that particular piece of wisdom?
    • AdrianC
    • By AdrianC 6th Sep 17, 10:54 PM
    • 15,096 Posts
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    AdrianC
    Can you point to any source for that particular piece of wisdom?
    Originally posted by Car 54
    Obvious, innit?

    An unidentified "tracking system" plus some footage from a cheap Chinese dashcam trump a trained operator using a calibrated, type-approved laser speed camera, any day of the week.

    Expert witnesses? The British public are tired of experts!
    • esmerobbo
    • By esmerobbo 7th Sep 17, 8:13 AM
    • 4,658 Posts
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    esmerobbo
    Once had a driver go to court with Tachograph (a calibrated device) and tracker evidence, he didn't do too well larger fine and 3 points plus a unpaid day off and brought to my notice that he was off route which cost him a bo11ocking!
    • Nilrem
    • By Nilrem 7th Sep 17, 11:24 AM
    • 2,308 Posts
    • 1,505 Thanks
    Nilrem
    What seems to be missing from the comments is an appreciation that two independent pieces of evidence should normally trump any single piece of evidence, however well calibrated the single piece of evidence may be.
    Infallible systems have so often proved to be flawed that there really should be no argument.
    Originally posted by brianposter
    Dashcam's don't necessarily show the moment that the speed gun caught him in a way that makes it easy/possible to work out the speed from distance travelled.

    And any GPS reading from a consumer device* is the average speed between the last X reading's it's processed from the satellites (accuracy to within X meters), on cheaper devices that can be quite a lag (next time you come to a complete stop in traffic suddenly watch your sat nav display, it can show you moving after the handbrake is applied).

    On cops side they've got a scientific instrument with a high level of redundancy/fail safe that is taking hundreds of measurements a second to give a reading (and if any two of those measurements are out of what it'll give an error).


    *As they can be affected a change in direction/level of travel.
    Last edited by Nilrem; 07-09-2017 at 11:26 AM.
    • Manxman in exile
    • By Manxman in exile 7th Sep 17, 12:08 PM
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    Manxman in exile
    Hopefully OP will shortly update on the evidence they receive from CSP.
    • bartelbe
    • By bartelbe 7th Sep 17, 2:19 PM
    • 378 Posts
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    bartelbe
    You can't beat a van equipped with laser equipment by slowing down when you see it. Which lets be honest, is what probably happened.

    By the time you see it, too late. Simple rule, if it is an area with camera vans, assume it there and keep below the speed limit.
    • DoaM
    • By DoaM 7th Sep 17, 2:40 PM
    • 3,214 Posts
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    DoaM
    You can't beat a van equipped with laser equipment by slowing down when you see it. Which lets be honest, is what probably happened.

    By the time you see it, too late. Simple rule, if it is an area with camera vans, assume it there and keep below the speed limit.
    Originally posted by bartelbe
    Fixed that for you.
    Diary of a madman
    Walk the line again today
    Entries of confusion
    Dear diary, I'm here to stay
    • onomatopoeia99
    • By onomatopoeia99 7th Sep 17, 3:23 PM
    • 3,348 Posts
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    onomatopoeia99
    If the OP were so minded, they could collect comparative data of their own on the dashcam and tracking device along a measured stretch of road driving at a constant indicated 29mph and back calculate the actual speed, so they can determine if their dashcam and tracking device are accurate.

    A proper court would accept that an "expert witness" is not required to measure a distance (a tape measure will do, one does not need to be an expert to operate a tape measure) or operate a stopwatch to measure an elapsed time travelling over the measured distance at a constant speed, nor to do a simple sum with those two pieces of information to calculate a velocity. One can calculate the accuracy of a device that measures speed very easily if prepared to spend a couple of hours ensuring you have a 1/4 mile measured up and do some drive by tests at the same constant speed the device previously measured with the aid of a friend.

    One benefit of doing that, is the OP would find out if his devices are accurate and that could inform his decision about whether to have his day in court or not.
    INTP, nerd, libertarian and scifi geek.
    Home is where my books are.
    • Manxman in exile
    • By Manxman in exile 13th Sep 17, 12:03 AM
    • 821 Posts
    • 542 Thanks
    Manxman in exile
    Thanks for all the input people; it is much appreciated.

    As I have mentioned, if I am guilty of the alleged offence then I have no problem with taking it on the chin and paying the £100 and doing the course. However, as discussed, my recollection - coupled with the evidence I have and that they have supplied - suggest to me that I didn't commit the offence.

    As I said, I spoke with the Camera Partnership yesterday (Tuesday) and they have said they will send out the evidence upon what they will be relying upon if it went to court. They said it should be with me by Thursday or Friday so I will update you once I have received this.

    Thanks once again for your input; much appreciated.
    Originally posted by AsaBlade

    May I ask if you've received anything to update us with yet? I thought you had to plead not guilty in order to see the evidence they would rely on in court.
    Last edited by Manxman in exile; 13-09-2017 at 12:06 AM. Reason: addition
    • wgl2014
    • By wgl2014 13th Sep 17, 8:51 AM
    • 277 Posts
    • 148 Thanks
    wgl2014
    If the OP were so minded, they could collect comparative data of their own on the dashcam and tracking device along a measured stretch of road driving at a constant indicated 29mph and back calculate the actual speed, so they can determine if their dashcam and tracking device are accurate.

    A proper court would accept that an "expert witness" is not required to measure a distance (a tape measure will do, one does not need to be an expert to operate a tape measure) or operate a stopwatch to measure an elapsed time travelling over the measured distance at a constant speed, nor to do a simple sum with those two pieces of information to calculate a velocity. One can calculate the accuracy of a device that measures speed very easily if prepared to spend a couple of hours ensuring you have a 1/4 mile measured up and do some drive by tests at the same constant speed the device previously measured with the aid of a friend.

    One benefit of doing that, is the OP would find out if his devices are accurate and that could inform his decision about whether to have his day in court or not.
    Originally posted by onomatopoeia99
    For personal amusement or whatever that's fine, for court though it would be useless. The issue is not that the OP would need an expert witness but that if the accuracy of the measuring equipment is questioned the prosecution would use one, if found guilty the OP would have to pay for them.
    • Car 54
    • By Car 54 13th Sep 17, 9:43 AM
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    Car 54
    For personal amusement or whatever that's fine, for court though it would be useless. The issue is not that the OP would need an expert witness but that if the accuracy of the measuring equipment is questioned the prosecution would use one, if found guilty the OP would have to pay for them.
    Originally posted by wgl2014
    Agreed.

    Also - although I've never tried - I suspect that measuring a quarter mile accurately would be very difficult without professional equipment. You won't find a 440 yard tape measure in Homebase.
    • Manxman in exile
    • By Manxman in exile 13th Sep 17, 11:56 AM
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    Manxman in exile
    Agreed.

    Also - although I've never tried - I suspect that measuring a quarter mile accurately would be very difficult without professional equipment. You won't find a 440 yard tape measure in Homebase.
    Originally posted by Car 54

    The OP may not be back for a while. I can picture them with an old wooden 12" ruler, turning it over 1320 times. And then losing count.
    • Aylesbury Duck
    • By Aylesbury Duck 13th Sep 17, 12:13 PM
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    Aylesbury Duck
    The OP may not be back for a while. I can picture them with an old wooden 12" ruler, turning it over 1320 times. And then losing count.
    Originally posted by Manxman in exile
    Nah, there's a much simpler way. Measure out 440 yards of string at home with the wooden ruler, go out and tie one end of it to a fixing point and mark the kerb with a blob of paint, run along the road until you run out of string and put a blob of paint on the kerbstone at the other end. Hey, presto! You have an accurately calibrated* distance of 440 yards.


    *the results may be affected by string tension, curvature of the road and curvature of the earth.
    • Manxman in exile
    • By Manxman in exile 13th Sep 17, 1:11 PM
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    Manxman in exile
    *the results may be affected by string tension, curvature of the road and curvature of the earth.
    Originally posted by Aylesbury Duck

    Yeah - but when you started to measure the string you'd have to remember to leave enough at the beginning to allow for the knot, which would need to be pretty substantial to keep the string in tension over 440yds. Otherwise you'd have to start all over again with another 440yds + piece of string. And if you didn't have another piece of string of that length, and if you were doing this at midnight (which is when I'd be doing it) you'd have to wait until the next day when the shops were open again, to buy some more string.


    (PS - I know this because in an earlier life I was a trainee Weights and Measures inspector. We used a lot of wooden rulers and string and spent a lot of time loitering outside hardware shops weighting (ha!) for them to open.)
    Last edited by Manxman in exile; 13-09-2017 at 1:21 PM. Reason: PS
    • facade
    • By facade 13th Sep 17, 2:31 PM
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    facade
    You could simply get a trundle wheel-or Surveyors wheel as the expensive ones would be called, but I doubt if you'd get much better than 2% accuracy over 1/4 mile
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science )
    • Aylesbury Duck
    • By Aylesbury Duck 13th Sep 17, 2:57 PM
    • 1,045 Posts
    • 1,267 Thanks
    Aylesbury Duck
    You could simply get a trundle wheel-or Surveyors wheel as the expensive ones would be called, but I doubt if you'd get much better than 2% accuracy over 1/4 mile
    Originally posted by facade
    Presumably you mean 98% accuracy? If not, that's a pretty poor surveyor's wheel. I'd get more accuracy from a hammer.
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