Camberwell Green 20mph Camera Question |
Camberwell Green 20mph Camera Question |
Wed, 21 Aug 2019 - 11:49
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#1
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Member Group: Members Posts: 162 Joined: 2 Nov 2014 From: London Member No.: 73,952 |
Hi Guys,
Here's a question. If someone was at the traffic light line on their motorbike and sped up past 20 to say 28(ish) mph before he got to the end of the dotted lines on the ground, would that trigger the camera. So for the camera in question where the blue van is; https://www.google.com/maps/@51.4787904,-0....6384!8i8192 If you were going from 0mph to 28 before the end of the dotted lines would that trigger the camera? Also do the Metropolitan Polce/Greater London area offer 20mph courses? Thanks! -------------------- Thanks CD |
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Wed, 21 Aug 2019 - 11:49
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Wed, 21 Aug 2019 - 12:36
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#2
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Member Group: Members Posts: 601 Joined: 7 May 2019 Member No.: 103,734 |
The speed is measured where the blue van is. You can see the sub-surface sensors on the road.
A vehicle passing between those black tar-filled lines has the time it arrives at the sensors measured, the distance is known so a speed can be calculated. Before and past the lines no speed is measured by the camera other than a secondary check speed from 2 photographs. If the speed is not above a set threshold speed from the sensors no secondary check images are taken. If you mean the dotted lines that form the crossing then you may well have your speed recorded in the circumstances you describe. If you mean the secondary check marks then probably not. |
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Wed, 21 Aug 2019 - 16:07
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#3
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Member Group: Members Posts: 162 Joined: 2 Nov 2014 From: London Member No.: 73,952 |
So;
If the bike was where the red box is and stationary waiting at a red light and then when the light went green accelerated up to just under 30mph possibly by the time it got to the end of the white lines, the 20mph trigger of the camera wouldn't deploy as the bike would have had to go over those black sensors at 20 when it was stationary? Thanks -------------------- Thanks CD |
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Wed, 21 Aug 2019 - 16:26
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#4
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Member Group: Members Posts: 38,007 Joined: 3 Dec 2010 Member No.: 42,618 |
Trigger point should be at least 24mph.
-------------------- If you would like assistance with a penalty charge notice, please post a thread on https://www.ftla.uk/index.php
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Wed, 21 Aug 2019 - 17:40
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#5
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Webmaster Group: Root Admin Posts: 8,205 Joined: 30 Mar 2003 From: Wokingham, UK Member No.: 2 |
From those images I reckon you'd need to accelerate at an average of about 0.53g to hit 24mph by the last line. From a standing start, with reaction time, maybe wheel spin, and a very non-linear torque curve, I think you'd be lucky to find many bikes that could achieve that. And that's without any of the issues around where the camera would trigger and the need for a secondary check when you've already left the check lines. I stand to be corrected, of course.
-------------------- Regards,
Fredd __________________________________________________________________________
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Thu, 22 Aug 2019 - 15:17
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#6
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Member Group: Members Posts: 38,007 Joined: 3 Dec 2010 Member No.: 42,618 |
From those images I reckon you'd need to accelerate at an average of about 0.53g to hit 24mph by the last line. I think you'd need your average speed between the lines to be 24 mph, so even if the rear wheel were to pass the last line at 25 or 26 mph, it's highly unlikely that the average speed as measured between the two lines would be measured at 24+ -------------------- If you would like assistance with a penalty charge notice, please post a thread on https://www.ftla.uk/index.php
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Thu, 22 Aug 2019 - 16:13
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#7
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Webmaster Group: Root Admin Posts: 8,205 Joined: 30 Mar 2003 From: Wokingham, UK Member No.: 2 |
Yes I know, but I assumed the OP's question was related to the (virtually) instantaneous primary speed measurement, not the average speed presumably inferred using the lines as a secondary check.
-------------------- Regards,
Fredd __________________________________________________________________________
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Thu, 22 Aug 2019 - 16:25
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#8
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Member Group: Members Posts: 38,007 Joined: 3 Dec 2010 Member No.: 42,618 |
What virtually instantaneous check? My understanding is that the primary measurement is taken from the two lines of senors buried in the road, and the secondary check is the two photos taken 0.5 seconds apart in combination with the dragon teeth?
-------------------- If you would like assistance with a penalty charge notice, please post a thread on https://www.ftla.uk/index.php
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Thu, 22 Aug 2019 - 16:32
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#9
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Webmaster Group: Root Admin Posts: 8,205 Joined: 30 Mar 2003 From: Wokingham, UK Member No.: 2 |
And how long do you imagine it takes to cross those two lines of sensors?
-------------------- Regards,
Fredd __________________________________________________________________________
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Thu, 22 Aug 2019 - 18:21
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#10
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Member Group: Members Posts: 38,007 Joined: 3 Dec 2010 Member No.: 42,618 |
And how long do you imagine it takes to cross those two lines of sensors? The question isn't how long it takes, but whether you can accelerate at such a rate that the average speed of the vehicle exceeds 24 mph while the rear wheel moved between the two lines. From your previous response we seem to be in agreement that this is possible but unlikely. -------------------- If you would like assistance with a penalty charge notice, please post a thread on https://www.ftla.uk/index.php
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Fri, 23 Aug 2019 - 20:01
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#11
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Member Group: Members Posts: 162 Joined: 2 Nov 2014 From: London Member No.: 73,952 |
Are we talking about the black lines in the road under the blue van as the motorbike was sat stationary on those black lines at a red light.
The light went green, the bike then would have accelerated to a speedo indicated 28mph-ish (so 25/26) by one point near or after the end of the white road markings. The bike in question can apparently do 0-60 in 3.1 seconds but I'd guess this start was nowhere near that at all! -------------------- Thanks CD |
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Sat, 24 Aug 2019 - 09:02
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#12
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Member Group: Members Posts: 601 Joined: 7 May 2019 Member No.: 103,734 |
Are we talking about the black lines in the road under the blue van as the motorbike was sat stationary on those black lines at a red light. The light went green, the bike then would have accelerated to a speedo indicated 28mph-ish (so 25/26) by one point near or after the end of the white road markings. The bike in question can apparently do 0-60 in 3.1 seconds but I'd guess this start was nowhere near that at all! The black lines are the speed detectors. As the bike is not moving there will be nothing to detect. As the bike moves off an acceleration is detected, no speed will be shown for the acceleration from 0mph to a higher speed than 0mph. |
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Sat, 24 Aug 2019 - 12:24
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#13
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Member Group: Members Posts: 162 Joined: 2 Nov 2014 From: London Member No.: 73,952 |
Are we talking about the black lines in the road under the blue van as the motorbike was sat stationary on those black lines at a red light. The light went green, the bike then would have accelerated to a speedo indicated 28mph-ish (so 25/26) by one point near or after the end of the white road markings. The bike in question can apparently do 0-60 in 3.1 seconds but I'd guess this start was nowhere near that at all! The black lines are the speed detectors. As the bike is not moving there will be nothing to detect. As the bike moves off an acceleration is detected, no speed will be shown for the acceleration from 0mph to a higher speed than 0mph. So basically there's zero chance of it having detected in those circumstances? -------------------- Thanks CD |
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Sat, 24 Aug 2019 - 15:17
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#14
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Member Group: Members Posts: 601 Joined: 7 May 2019 Member No.: 103,734 |
Are we talking about the black lines in the road under the blue van as the motorbike was sat stationary on those black lines at a red light. The light went green, the bike then would have accelerated to a speedo indicated 28mph-ish (so 25/26) by one point near or after the end of the white road markings. The bike in question can apparently do 0-60 in 3.1 seconds but I'd guess this start was nowhere near that at all! The black lines are the speed detectors. As the bike is not moving there will be nothing to detect. As the bike moves off an acceleration is detected, no speed will be shown for the acceleration from 0mph to a higher speed than 0mph. So basically there's zero chance of it having detected in those circumstances? Basically or exactly, whichever you prefer. |
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Sat, 24 Aug 2019 - 23:01
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#15
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Member Group: Members Posts: 162 Joined: 2 Nov 2014 From: London Member No.: 73,952 |
Lol got it thanks :-)
-------------------- Thanks CD |
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