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#Post#: 119224--------------------------------------------------
Speeding NIP incorrectly calculating speed?
DIR By: radiola92
Date: May 19, 2026, 10:17 am
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Hi everyone.
I just received a NIP alleging I was driving 80 on a dual
carriageway. I went to check the evidence as I remember
potentially being a bit over the 70 limit for a moment and then
reducing my speed.
What I noticed was that the first picture shows a long distance
picture of a car which looks similar to mine but the number
plate isn't legible going at 80mph with a timestamp of 12:26:05
and D=0352.7m. The second picture has my actual car (number
plate is legible) in a different lane to the car in the first
picture going at 64mph with a timestamp of 12:26:14 and
D=0079.4m.
I assume D is distance, so I calculated that the distance
between the 2 pictures is 273.3m and that there is a difference
of 9 seconds so the average speed over that 9 seconds is
approximately 30.37 m per second which is roughly 109.32 km per
hour or 67.9283 mph.
If I assume that the first picture is indeed my car, don't these
calculations prove or at least reasonably suggest that I was in
fact driving at below the 70 speed limit? Is this a reasonable
defence?
Many thanks for any comments or suggestions!
#Post#: 119225--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: JustLoveCars
Date: May 19, 2026, 10:26 am
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Without the pictures or knowing what sort of camera was involved
it's impossible for us to say. (Or at least give the location)
However, using such time over distance calculations where an
instantaneous capture method was employed is generally
fruitless.
#Post#: 119226--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: radiola92
Date: May 19, 2026, 10:36 am
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--- Quote from: JustLoveCars link ---
>
> Without the pictures or knowing what sort of camera was
involved it's impossible for us to say. (Or at least give the
location)
>
> However, using such time over distance calculations where an
instantaneous capture method was employed is generally
fruitless.
>
--- End Quote ---
Thanks, the calibration certificate says the camera is a Kustom
LaserCam 4 Speed Meter and it was on the A11 around Red Lodge,
Suffolk.
#Post#: 119228--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: andy_foster
Date: May 19, 2026, 10:40 am
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The time displayed is "live". The speed and distance are not.
The distance travelled between the 2 pings could well be greater
than the difference in the distances, and using whole seconds as
a unit of measurement over ~9 seconds adds a potential error of
+/- 11%, in addition to the uncertainty as to when the distances
were actually measured.
#Post#: 119229--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: JustLoveCars
Date: May 19, 2026, 10:41 am
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--- Quote from: radiola92 link ---
>
> [quote author=JustLoveCars
link=topic=10878.msg119225#msg119225 date=1779204398]
> Without the pictures or knowing what sort of camera was
involved it's impossible for us to say. (Or at least give the
location)
>
> However, using such time over distance calculations where an
instantaneous capture method was employed is generally
fruitless.
>
--- End Quote ---
Thanks, the calibration certificate says the camera is a Kustom
LaserCam 4 Speed Meter and it was on the A11 around Red Lodge,
Suffolk.
[/quote]
...then your time over distance calculations won't provide a
defence.
Your speed was measured virtually instantaneously (Around 1/3s)
- that peak/measured speed is all that matters.
#Post#: 119247--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: radiola92
Date: May 19, 2026, 2:01 pm
---------------------------------------------------------
--- Quote from: JustLoveCars link ---
>
> [quote author=radiola92 link=topic=10878.msg119226#msg119226
date=1779204961]
> [quote author=JustLoveCars
link=topic=10878.msg119225#msg119225 date=1779204398]
> Without the pictures or knowing what sort of camera was
involved it's impossible for us to say. (Or at least give the
location)
>
> However, using such time over distance calculations where an
instantaneous capture method was employed is generally
fruitless.
>
--- End Quote ---
Thanks, the calibration certificate says the camera is a Kustom
LaserCam 4 Speed Meter and it was on the A11 around Red Lodge,
Suffolk.
[/quote]
...then your time over distance calculations won't provide a
defence.
Your speed was measured virtually instantaneously (Around 1/3s)
- that peak/measured speed is all that matters.
[/quote]
Thanks for clarifying that.
In the first picture (around 350m away) the car's number plate
isn't legible but in the second picture (around 80m away) it is
legible but the car is in a different lane. It seems to me that
unless there is video footage of the car from the first picture
moving into the other lane and showing the number plate coming
into view, it can't be proven that the car going over the limit
in the first picture is the same one as the car in the second
picture which is under the limit. Do you know if that camera
records video footage and can I request it as evidence?
#Post#: 119251--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: JustLoveCars
Date: May 19, 2026, 2:47 pm
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--- Quote from: radiola92 link ---
>
> Do you know if that camera records video footage and can I
request it as evidence?
>
--- End Quote ---
Yes it does. Short of rejecting all out of court offers
(Course/Fixed Penalty) they are unlikely supply any such
footage. (Then you are subject to court sentencing if
convicted)
#Post#: 119289--------------------------------------------------
Re: Speeding NIP incorrectly calculating speed?
DIR By: BertB
Date: May 20, 2026, 5:38 am
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Is there a vehicle the same make, model and colour as yours in
the first image? Is likely that having pinged you, the operator
turned round to do something else, returned to his camera 9
seconds later and then thought oh, I'll get a closer image of
that vehicle I just pinged, and captured yours instead having
missed the faster vehicle going under the bridge?
Or is it more likely you reduced speed and changed lanes, all
the while being recorded by the camera's video?
I'm not sure I would want to turn down a SAC or COFP based on
that assumption.
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