People that don’t go the average speed

[grudas]

there are a few different types of cameras but the concept is the same

snap 1
snap 2
time traveled between snaps = speed

anything above the usual 10% above limit = record -> fine

https://www.theaa.com/driving-advice/legal/speed-c...

[jondude]

IJWS15 said:

I

It is the idiots doing dead on 50 in the outside lane holding everyone else up that annoy me.

A problem on the A127 from Southend towards London is the average speed cameras cause quite incredible bunching in busy times and there is a slip road to a roundabout near Rayleigh that often has a tailback way, way onto the A127.

If you do not get over to the right early and are forced to slow or stop on the left due to the jam, no-one but no-one is now going to let you in on the right due to the bunching and the line moving at 40-50 odd mph. Indeed, if on the right and you want to help it is often impossible as the driver behind you is up your backside.

So while the locals are appearing to drive inconsiderately, they are, in fact, aiding traffic flow by avoiding that last minute attempt to barge to the right.

All a bit messy though, agreed.

[LunarOne]

Osinjak said:

I think the distances between cameras is fixed (200m maybe?) so someone who's good with numbers would be able to work it out.

The distance between cameras is much greater than 200m. It's typically more like 2km. But there's no reason that the camera pairs that you are timed between have to be consecutively placed. From what I've read, the camera pairs are often further apart. So that overlapping distances are measured. For example 3 pairs marked A1+2, B1+2 and C1+2 as follows:

A1-------------------B1----------------C1---------------A2--------------B2---------------C2


This gives the benefit of having regular timed sections while still having time measured over a large enough distance to reduce error significantly.

I used to have to do the M4 average speed zone twice daily, and I even had cruise control retrofitted to my car for peace of mind. I pinned it on an indicated 55mph which I knew from GPS was a true 53mph. That's well within the 10%+2 prosecution tolerance of 57, and it also gave me a small allowance to get past people like WJNB even if it meant sliding past them in lanes one or two.

[Cliftonite]

mattyprice4004 said:

WJNB said:

I'm happy to be "an idiot in the outside lane" doing 50mph. It means I'm not sandwiched amidst the HGV's & if prats want to tail-gate me because I refuse to speed then tough I just gently ease off the throttle or click down on the cruise control.

Poor attempt at trolling; no one is that stupid.

Never under-estimate the possible extent of stupidity!

[AndyAudi]

A1Diego said:

What is it with those that just ignore the average speed and happily go 70mph or those that speed up between cameras and brake back down to 50 at the next set of yellow cameras.

What do they know that most people that follow the rules don’t???

Maybe they know their current actual average, As soon as I hit an average speed camera I reset my trip, cruise control set & carry on. Now if I’ve been held up by something before hitting the next camera I do increase my speed to return to an acceptable average or have a bit of fun. (In theory a mile at 60 & a mile at 90 is a two mile average of 75) This does sometimes mean dropping speed back to an acceptable limit when approaching a fresh camera. (Scottish Dual Carriageways with miles between cameras not blasting through roadworks)

[Chozza]

[quote=LunarOne]

The distance between cameras is much greater than 200m. It's typically more like 2km. But there's no reason that the camera pairs that you are timed between have to be consecutively placed. From what I've read, the camera pairs are often further apart. So that overlapping distances are measured. For example 3 pairs marked A1+2, B1+2 and C1+2 as follows:

A1-------------------B1----------------C1---------------A2--------------B2---------------C2


/quote]

I had always assumed that the average was between ANY two points.
So A1-B1 , A1-C1 , A1 -A2 , A1 -B2 , A1 -C2 , B1 -C1 , B1 -C2 etc .. If you exceed the speed between any combination of points the you must have been speeding - so 15 possible combinations and potentially have independent data points as well , so able to cross check and cope with failed camera/obscured number plates behind other vehicles etc.
Not much data to process , since the anpr has already captured the plate.

[LunarOne]

That's also a possibility I had considered, but I haven't seen that suggested in writing.

[Mr Tidy]

Jediworrier said:

I'm astounded that had to be explained!

I'm not - it just about sums things up!

[QuickQuack]

AndyAudi said:

Maybe they know their current actual average, As soon as I hit an average speed camera I reset my trip, cruise control set & carry on. Now if I’ve been held up by something before hitting the next camera I do increase my speed to return to an acceptable average or have a bit of fun. (In theory a mile at 60 & a mile at 90 is a two mile average of 75) This does sometimes mean dropping speed back to an acceptable limit when approaching a fresh camera. (Scottish Dual Carriageways with miles between cameras not blasting through roadworks)

Not quite, that's not how average speed works. At 60mph, you take 1 minute to travel 1 mile. At 90mph, you take 40 seconds to travel 1 mile. You've travelled 2 miles in 1 minute 40 seconds which equates to 72mph, not 75mph. Error is small as the distance is relatively small.

Here's a trick question: in an average speed section between 2 cameras, if you travel the first half of the distance at half the speed limit, how fast can you travel in the second half so that you don't go over the average limit?

[unident]

QuickQuack said:

Not quite, that's not how average speed works. At 60mph, you take 1 minute to travel 1 mile. At 90mph, you take 40 seconds to travel 1 mile. You've travelled 2 miles in 1 minute 40 seconds which equates to 72mph, not 75mph. Error is small as the distance is relatively small.

Here's a trick question: in an average speed section between 2 cameras, if you travel the first half of the distance at half the speed limit, how fast can you travel in the second half so that you don't go over the average limit?

An infinite speed, as you’ve already used the minimum allowable time up by going half speed for half the distance, so whatever speed you do you will average less than the maximum speed.

[speedking31]

QuickQuack said:

Here's a trick question: in an average speed section between 2 cameras, if you travel the first half of the distance at half the speed limit, how fast can you travel in the second half so that you don't go over the average limit?

Einstein won't allow you to go that fast

[AndyAudi]

QuickQuack said:

Not quite, that's not how average speed works. At 60mph, you take 1 minute to travel 1 mile. At 90mph, you take 40 seconds to travel 1 mile. You've travelled 2 miles in 1 minute 40 seconds which equates to 72mph, not 75mph.

I’m ashamed, Obvious when you write it like that!
(Just as well I’d leave the car to figure it out!).

[IJWS15]

WJNB said:

I'm happy to be "an idiot in the outside lane" doing 5045 mph because I don't know my speedo doesn't read correctly. It means I'm not sandwiched amidst the HGV's & if prats want to tail-gate me because I refuse to speed then tough I just gently ease off the throttle or click down on the cruise control.

FTFY

[Pothole]

Jediworrier said:

Grayedout said:

Sorry they don't. They read your numberplate and note the time you passed that point, they know the distance from the last camera and they then calculate your average!

Distance travelled / Time taken !

I'm astounded that had to be explained!

I'm astounded the whoosh parrot wasn't obvious to either of you!

[LunarOne]

IJWS15 said:

WJNB said:

I'm happy to be "an idiot in the outside lane" doing 5045 mph because I don't know my speedo doesn't read correctly. It means I'm not sandwiched amidst the HGV's & if prats want to tail-gate me because I refuse to speed then tough I just gently ease off the throttle or click down on the cruise control.

FTFY

We don't know whether he meant an indicated 50 or a true 50. But I really hope nobody's speedo is overreading by 5mph at only 45. That would be some error! Mine does 48 at an indicated 50, and 67 at an indicated 70 and I thought that was pretty terrible.

Now that we've mostly dispensed with a spinning magnet in a cup and use digital speed sensors, surely it would be a simple matter to have the car calibrate its speedometer against its own GPS speed at intervals to automatically account for tyre wear. Perhaps every time the car does a steady speed in a straight line with low GPS dilution of precision available.

[unident]

LunarOne said:

We don't know whether he meant an indicated 50 or a true 50. But I really hope nobody's speedo is overreading by 5mph at only 45. That would be some error! Mine does 48 at an indicated 50, and 67 at an indicated 70 and I thought that was pretty terrible.

Now that we've mostly dispensed with a spinning magnet in a cup and use digital speed sensors, surely it would be a simple matter to have the car calibrate its speedometer against its own GPS speed at intervals to automatically account for tyre wear. Perhaps every time the car does a steady speed in a straight line with low GPS dilution of precision available.

How much does tyre wear really affect the reading? I’m sure someone with better maths than me can work it out but a couple of mm off a large wheel and tyre won’t affect things much at all I’d have thought.

[Terminator X]

A1Diego said:

Hey guys,

Been curious about this for ages especially now I do many miles on the m4 where we have an average speed zone of 50mph for miles upon miles.

What is it with those that just ignore the average speed and happily go 70mph or those that speed up between cameras and brake back down to 50 at the next set of yellow cameras.

What do they know that most people that follow the rules don’t???

Didn't pay attention at school when average was discussed in maths?

TX.

[Terminator X]

Osinjak said:

bearman68 said:

Can't be true - if it was there would only be 2 cameras - one at the start, and one at the end. But there's loads. So they must be averaging you speed as you pass them. Stands to reason.

Only it doesn't. The system requires two paired cameras but there's no limit to how many can be used nor in what sequence. You could have ten cameras with just the camera at either end or you could have four in two pairs or two in a chain of four and so on. So the question is, do you feel lucky?

At night you can see which ones are "on" as there is a UV glow from them vs others that don't eg those ones are dummies / not turned on. I still wouldn't chance it though which is why the average camera's pain me so.

TX.

[Tankrizzo]

Do you ever post and then think "ah crap I forgot to sign it with the Terminator thing" and then go back and edit it?

Just musing.

[Mandat]

Osinjak said:

bearman68 said:

Can't be true - if it was there would only be 2 cameras - one at the start, and one at the end. But there's loads. So they must be averaging you speed as you pass them. Stands to reason.

Only it doesn't. The system requires two paired cameras but there's no limit to how many can be used nor in what sequence. You could have ten cameras with just the camera at either end or you could have four in two pairs or two in a chain of four and so on. So the question is, do you feel lucky?

It doesn't matter which cameras are paired together.

As long as the average speed between any two consecutive cameras is below the prosecution threshold, then the average speed along the whole enforcement area can never be higher, irrespective of how many cameras there are.