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PostPosted: Tue Feb 28, 2006 11:22 
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Do Specs networks calculate the distance over the whole network or just the camera pairs ??

Was on the A616 and speeded up to 70 (daft I know) in a 60 zone before slowing down below 60 on seeing the camera approaching (I never realised it was there). I don't think i did it for long but are still slightly worried.

Obviously i realise that the speedo is about 3-4 mph out.


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PostPosted: Tue Feb 28, 2006 11:43 
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You should be alright - ACPO prosecution threshold is 68 in a 60 minimum. It's likely that 70 indicated is about 67-68 anyway.


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PostPosted: Tue Feb 28, 2006 11:54 
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The aim of SPECs is to snare all offending drivers, so I would think the system measures a vehicle speed between the previous and the next camera - over the entire network; after-all, it’s just two time stamps, locations (for distance) and digital pictures transmitted over a network.
There’s no safety (SCP term for ‘financial’) benefit of having ‘dead zones’ between cameras
(I would be happy to be proven wrong)


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PostPosted: Tue Feb 28, 2006 12:14 
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smeggy wrote:
The aim of SPECs is to snare all offending drivers, so I would think the system measures a vehicle speed between the previous and the next camera - over the entire network; after-all, it’s just two time stamps, locations (for distance) and digital pictures transmitted over a network.
There’s no safety (SCP term for ‘financial’) benefit of having ‘dead zones’ between cameras
(I would be happy to be proven wrong)


True, though I meant that the the calculation would be taken over all of the cameras on the "network" and then the average taken.

Doing 70 on the speedo calculates as 66 on my sat nav, whereas 60 is 56/7. I suppose the sat nav will be more accurate ??


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PostPosted: Tue Feb 28, 2006 12:18 
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hullmackem wrote:
smeggy wrote:
The aim of SPECs is to snare all offending drivers, so I would think the system measures a vehicle speed between the previous and the next camera - over the entire network; after-all, it’s just two time stamps, locations (for distance) and digital pictures transmitted over a network.
There’s no safety (SCP term for ‘financial’) benefit of having ‘dead zones’ between cameras
(I would be happy to be proven wrong)


True, though I meant that the the calculation would be taken over all of the cameras on the "network" and then the average taken.

If they were going to do that then the intermediate cameras would serve no function.

I would expect that each time you pass a camera the speed from the previous one is calculated and dealt with as an individual measurement. Once they have done so there is clearly no need to take a further average over the whole section, as in order to have recorded an illegal overall average you would have to have been going at least that fast through one of the intermediate sections.

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PostPosted: Tue Feb 28, 2006 12:54 
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hullmackem wrote:
True, though I meant that the the calculation would be taken over all of the cameras on the "network" and then the average taken.

I did wonder if that’s what you meant.
As far as the law is concerned, you only need to briefly blip over the limit for an offence to be committed. Think about it this way: assuming a 70mph limit throughout, you travel through one set of cameras with an average speed of 90, then the next camera at 50. Your net average speed will be (around) 70mph but an offence was committed (and detected) regardless; the SCPs will prosecute!

hullmackem wrote:
Doing 70 on the speedo calculates as 66 on my sat nav, whereas 60 is 56/7. I suppose the sat nav will be more accurate ??

Sat Nav are targeted to give perfect accuracy, speedos are targeted to give inaccurate readings (over-read), hence Sat Nav is usually more accurate.


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PostPosted: Tue Feb 28, 2006 13:11 
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smeggy wrote:
hullmackem wrote:
True, though I meant that the the calculation would be taken over all of the cameras on the "network" and then the average taken.

I did wonder if that’s what you meant.
As far as the law is concerned, you only need to briefly blip over the limit for an offence to be committed. Think about it this way: assuming a 70mph limit throughout, you travel through one set of cameras with an average speed of 90, then the next camera at 50. Your net average speed will be (around) 70mph but an offence was committed (and detected) regardless; the SCPs will prosecute!

hullmackem wrote:
Doing 70 on the speedo calculates as 66 on my sat nav, whereas 60 is 56/7. I suppose the sat nav will be more accurate ??

Sat Nav are targeted to give perfect accuracy, speedos are targeted to give inaccurate readings (over-read), hence Sat Nav is usually more
accurate.


Cheers, thought so.
I tend to panic whenever I get near speed cameras as I use the car for work a lot. Generally 66mph will not prosecuted ??? though I suppose it depends on the partnership and police. Anyone know what South Yorks prosecute at ?


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PostPosted: Tue Feb 28, 2006 13:55 
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We've never really had a definitive answer on whether SPECS does operate only between specific pairs of "start" and "end" cameras, or between all cameras in a system.

I would expect there to be dead zones where the A616 goes through the A61 roundabout, and where the A77 goes through 30-limit villages.

The cameras on the A616 do appear to be in pairs with longer gaps between the pairs.

It's impossible for the brain to deal easily with the concept of calculating a rough average speed over a stretch of road, and therefore SPECS makes people feel they must avoid exceeding the limit by much anywhere within the zone.

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