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piattj



Member Since: 18 Jan 2012
Location: where the crowds aint...
Posts: 1235

Wales 2011 Freelander 2 SD4 GS Auto Baltic Blue
A9. Average speed cameras.

Travelling back from a stay in the Highlands this weekend, I travelled up and came down the A9 (South from Inverness). The whole A9 seems to be a never-ending stream of average speed cameras. This set me wondering how they work. Is your average speed determined multiple times along the road, taking average speed between one camera and the next, or is it avaraged over your whole journey along the A9, or some combination of both?
Along the A9, there are many useful stretches of dual carriageway, allowing for safe overtaking. I know these stretches have a 70, rather than 60 MPH limit so the cameras must take that into account when calculating average speed of a specific vehicle?
I must say that the A9 journey was uneventful, in that no-one was speeding, traffic flowed at 55-60 very smoothly and nobody tried to intimidate you into going faster. I found myself with cruise control set to 58, with nary another car in sight for mile after mile. Rather a refreshing change from the hurly-burly of the M6 etc. ...

Be true to yourself. That way happiness lies...

Post #264009 17th May 2015 1:44 pm
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MidlandRover



Member Since: 30 Jun 2013
Location: Derby
Posts: 496

England 2014 Freelander 2 SD4 Metropolis LE Auto Santorini Black

Same thing on the M1 right now and it got me wondering too,
I accept that speedos are pessimistic but I always stick to the posted limit of 50 and still people are going past a specially trucks, do they ever get a ticket?, who knows. FL2 SD4 Metropolis Auto Santorini Black / ivory completely stock.

It's true that light travels faster than sound, some people look quite intelligent until you hear them speak.


Stop global winging.

Post #264011 17th May 2015 2:48 pm
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Navigator



Member Since: 29 Dec 2010
Location: Within reach of the coffee machine
Posts: 492

Scotland 

I understand these work between any two adjacent gantries. So those who use a stretch of road frequently know if there is not another gantry before they turn off and can go like a bat out of hell with no sanctions. Everyone can spread it - Anyone can catch it. Stay home - the life you save can be your own!

Post #264013 17th May 2015 3:28 pm
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andyk159



Member Since: 19 Nov 2014
Location: Skegby
Posts: 368

United Kingdom 2010 Freelander 2 TD4 HSE Auto Stornoway Grey

If it's like the setup on the A77, they can track between any pair of multiple of cameras at will.

How this is applied in any particular period is up to police. Andy
Freelander2 HSE (59 Plate, MY10 spec)

Post #264015 17th May 2015 3:54 pm
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Chuckalicious



Member Since: 23 May 2014
Location: Midlothian
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United Kingdom 2014 Freelander 2 SD4 SE Auto Santorini Black

I use the southern most part of the A9 regularly and it is lovely not having tools trying to run into the back of you to get past.

I understand there is frustration on the single lane bits where people can get stuck behind lorries which have a lower limit but otherwise I think it is great. No need to speed, or at least I find no need to so it makes the journey far nicer.

As for the dual carriageway parts, you would assume they calculate based on a 70 limit rather than a 60. Learned to drive in 2011.
Bought a Micra - great little car
"Upgraded" to Kia Sportage - hated it
Proper upgrade to FL2 TD4 GS 60 reg Facelift - tailgate paint issues, fuel gauge rewire, transfer box failure at 36k miles, clutch at 60k
Reconditioned diff at 70k ish
Sold at 84k and now on a DS. Terribly unreliable.
Sold DS for a 2021 Mitsubishi Outlander PHEV. Fingers crossed....
Sold Outlander for a 2014 SD4 SE Tech because I’m mental

Post #264016 17th May 2015 3:55 pm
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choccymonster



Member Since: 27 Sep 2013
Location: Chichester, West Sussex
Posts: 513

United Kingdom 2007 Freelander 2 TD4 HSE Manual Tambora Flame

I believe AndyK159 is correct.

Average speed is calculated by two random cameras.

i.e. Your speed may not be simply calculated between one gantry and the next - it might be between gantry one and six (for example), with gantries two through five not performing any function.

As suggested, the gantries that are used can be changed as the situation demands.

Anecdotal evidence suggests that the newer versions of the software can determine for themselves which gantries to use. i.e. Car 1 might have their average speed measured between gantry 1 and 3, whereas car 2 might be measured between gantry 1 and 6......

Not sure how true that is, but it sounds plausible.

Post #264017 17th May 2015 4:02 pm
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piattj



Member Since: 18 Jan 2012
Location: where the crowds aint...
Posts: 1235

Wales 2011 Freelander 2 SD4 GS Auto Baltic Blue

Sounds entirely plausible, with software. Key is keep to the limit! Very Happy ...

Be true to yourself. That way happiness lies...

Post #264027 17th May 2015 6:11 pm
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MidlandRover



Member Since: 30 Jun 2013
Location: Derby
Posts: 496

England 2014 Freelander 2 SD4 Metropolis LE Auto Santorini Black

There are 6 cameras on a stretch of road I used to use in Yorkshire with 3 on each side, rumour has it that only 3 are working at any time but no one knows which ones. FL2 SD4 Metropolis Auto Santorini Black / ivory completely stock.

It's true that light travels faster than sound, some people look quite intelligent until you hear them speak.


Stop global winging.

Post #264056 17th May 2015 9:35 pm
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Navigator



Member Since: 29 Dec 2010
Location: Within reach of the coffee machine
Posts: 492

Scotland 

Chuckalicious wrote:
stuck behind lorries which have a lower limit

One of the first changes to speed limits under devolved powers was to INCREASE the speed limit for lorries on the single carriageway parts of the A9. I understand there are now signs displayed for all to see. Everyone can spread it - Anyone can catch it. Stay home - the life you save can be your own!

Post #264091 18th May 2015 10:16 am
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alans835



Member Since: 14 May 2015
Location: Highlands
Posts: 67

Scotland 2011 Freelander 2 SD4 Sport Auto Fuji White

I use the A9 a fair bit and there is now signs saying that lorries can do 50MPH which helps a lot. The dual carriage way sections on the A9 between Inverness and Perth are not part of the average speed camera range which helps too allow you to clear traffic quick as some of these section are not very long. I was under the impression that the cameras only work between each other rather than 1 calculated journey time over them all. However that was just what we have heard up in bonnie highlands could well be wrong. Regards

Alan

Post #264269 20th May 2015 5:00 am
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