Speeding through average speed camera zones - What gives?

[xRIEx]

speedking31 said:

xRIEx said:

Possibly a separate debate, but I did read that tread depth makes minimal difference to rolling circumference, as the steel belt is the limiting part of the tyre construction. The closest approximation for this value can be calculated by taking the outer diameter, subtracting twice the tread depth and multiplying by PI. Roughly speaking, that's 0.96 x OD x PI."

Hardly makes any difference to the sums.

For a 215/45/17 the diameter is 625 mm. Say 7 mm of tread wear (x 2) = 2.2%.

For 2 mm tread the rolling circumference is (625 - 2 x 2) x ? = 1952 mm.
For 9 mm tread the rolling circumference is (625 - 2 x 9) x ? = 1908 mm.
Difference = 44 mm = 2.3%.

Weren't you the one claiming it made enough difference for manufacturers to account for it in speedo readings? Are you now claiming it doesn't make enough difference?

[timberman]

xRIEx said:

sicasey said:

xRIEx said:

I don't think they are average speed cameras; the boxes behind the signs look remarkably like gatsos.

Are they infarct only enabled when the reduced speed is illuminated?

I've heard claims that they will trigger at 90 even when not illuminated - I've not tested that myself, but I have been travelling at, ahem, something over 70mph and had people passing me under the gantries and still no flash; I would estimate that 85 on the clock (depending on car) wouldn't trigger anything, even if they are active in those situations.

I travel up and down the m1 a lot between junctions 27 and 21 and can tell you that only about a 3rd of the overhead gantries actually have cameras fitted.

[S3_Graham]

essIII said:

I set my cruise to 56mph whenever in a 50 average (going off the "10% +1 = safe" logic) - done many miles in both the M1 and M3 stretches and not had any issues with tickets. I do often wonder what's going on when someone comes past me at 70ish though!

I do exactly the same. 55 on the cruise control. The number of tossers that do 45-50 and flat out refuse to move over is infuriating! If people want to sail past me at 70, crack on!

[DavidJG]

timberman said:

I travel up and down the m1 a lot between junctions 27 and 21 and can tell you that only about a 3rd of the overhead gantries actually have cameras fitted.

That many? The Birmingham M42 / M6 has a lot of camera boxes, but seems to only have one, or maybe two, camera(s) that moves around between various boxes.

[speedking31]

xRIEx said:

Weren't you the one claiming it made enough difference for manufacturers to account for it in speedo readings? Are you now claiming it doesn't make enough difference?

I am showing a reason for deviation of the speedo display that the manufacturer must allow for when ensuring that his speedo does not underread, i.e. an unavoidable reason why speedos cannot be 100% accurate all the time.

Whether the rolling circumference is calculated simply or using the more accurate formula makes an insignificant difference to the calculated effect of tyre wear on the speed display.

Edited by speedking31 on Thursday 11th February 16:24

[krarkol]

SturdyHSV said:

As has sort of been covered:

Speedos read up to 10% over. So that's an indicated 55mph.

Most counties use the ACPO guidelines of 10% + 1. That means 56mph is allowed.

Add on your 10% speedo error and you're up at an indicated ~61mph already!

The ACPO guidelines 10% is there to cover the fact your speedo has a 10% error. You don't get both!

I drive at around an indicated 55mph btw. Hate the things, especially when its like 4am and there's only me trundling along at 50mph with not another soul in sight!

[xRIEx]

speedking31 said:

xRIEx said:

Weren't you the one claiming it made enough difference for manufacturers to account for it in speedo readings? Are you now claiming it doesn't make enough difference?

I am showing a reason for deviation of the speedo display that the manufacturer must allow for when ensuring that his speedo does not underread, i.e. an unavoidable reason why speedos cannot be 100% accurate all the time.

Whether the rolling circumference is calculated simply or using the more accurate formula makes an insignificant difference to the calculated effect of tyre wear on the speed display.

Edited by speedking31 on Thursday 11th February 16:24

It carries the same significance to both - if it's significant for one, it must be significant to the other; it's negligible to one, it must be negligible to the other.

If the height of tread from the steel belt is insignificant, then the wearing of that tread must be less significant (as it is a lower %age than the rolling circumference). I posit that the tread wear is zero signficance.

[speedking31]

I'm not trying to have an argument with you. I reckon that treadwear could have a 2% effect on speedo reading. That cannot be compensated in real time by the manufacturer. Therefore the speedo has to be inaccurate (sometimes) so that it never underreads. This is compounded by other tolerance effects.

[Pete317]

xRIEx said:

AJordan said:

If this is the case, then it proves surely proves that the cameras are solely there to generate revenue,

IIRC the 50mph limit is because the barriers used between the carriageway and the roadworks are type approved up to 50mph.

So they'll stop a 44-tonner doing 50mph, but not a motorcycle doing 70mph?

[V8RX7]

sicasey said:

numerous drivers pass me at up to 70 MPH.

what do they know that I don't?

That their car isn't registered to their name and / or address.

A mate did this and went through numerous cameras got away with it for a year - then they caught up with him through the insurance database - he's due in court shortly and expecting a ban.

[WD39]

forzaminardi said:

I've been up and down the M1 a lot over the past 6 months. I set my cruise control at 54 and generally find myself passing everyone else at a steady rate. I've not had anyone except those properly 'going for it' pass me that I can recall, nor (so far) had a ticket. It's worth noting that in both the 50 average zones Southbound around Nottingham and Northbound before Sheffield, the first camera is quite some way after the 50 zone begins, so that's a bit of a free for all for anyone who realises.

I recall just after New Year heading south being overtaken at a huge speed by an Infiniti saloon thing (only time I've ever seen one on the road). As we came up to a camera he braked, cut in close behind a truck, went past the camera then pulled out and carried on at 70+. Seemed like a rather foolish/brave tactic to me.

I find it annoying when people are going along at 48-50ish (fair enough) but then slow to 40-45 (why!?!) as they pass the camera.

I would suggest that most drivers slow down for traffic cameras.

They want the security of not getting a ticket and all the associated hassle involved.

Yes, I know it is irrational.

[WD39]

S3_Graham said:

essIII said:

I set my cruise to 56mph whenever in a 50 average (going off the "10% +1 = safe" logic) - done many miles in both the M1 and M3 stretches and not had any issues with tickets. I do often wonder what's going on when someone comes past me at 70ish though!

I do exactly the same. 55 on the cruise control. The number of tossers that do 45-50 and flat out refuse to move over is infuriating! If people want to sail past me at 70, crack on!

Why are they tossers? Keeping to the recommended speed limit would seem the correct course of action.

Crack on indeed.

[Bonefish Blues]

Because keep left unless overtaking applies in these zones too.

[xRIEx]

Pete317 said:

xRIEx said:

AJordan said:

If this is the case, then it proves surely proves that the cameras are solely there to generate revenue,

IIRC the 50mph limit is because the barriers used between the carriageway and the roadworks are type approved up to 50mph.

So they'll stop a 44-tonner doing 50mph, but not a motorcycle doing 70mph?

I highly doubt it. It's a valid point, maybe raise it with the committee that decide on the type approval regs?

[WD39]

Bonefish Blues said:

Because keep left unless overtaking applies in these zones too.

'Everyone's got themselves into a big damn hurry.' ( Brooks- The Shawshank Redemption.)

[227bhp]

EazyDuz said:

Timbola said:

and workmen may be present.

That part made me laugh

Not as much as I do at the signs with pics of kids which read "Drive carefully, my Mum works here".
No she doesn't, she really doesn't.

There are 2 ways around these SPECS cameras, one is they can't see in the dark, the other is to place yourself strategically by another vehicle so they can't read your plate.

[Pete317]

xRIEx said:

Pete317 said:

xRIEx said:

AJordan said:

If this is the case, then it proves surely proves that the cameras are solely there to generate revenue,

IIRC the 50mph limit is because the barriers used between the carriageway and the roadworks are type approved up to 50mph.

So they'll stop a 44-tonner doing 50mph, but not a motorcycle doing 70mph?

I highly doubt it. It's a valid point, maybe raise it with the committee that decide on the type approval regs?

Oh, I have no doubt that they're well aware of it

[Revisitph]

I understood that the overhead gantry variable speed limit (not average limit) cameras were active when a variable limit was in place but were not when nothing was illuminated i.e. when the 70mph limit was in force. Source of information was the news about a police chief a few months ago, complaining about budget cuts and threatening to switch on the cameras continuously (so at 70 when no variable limit displayed) as a necessary money raising measure.

Ah! my memory isn't that bad: here it is (also articles in the Wail on the same topic) http://www.thisismoney.co.uk/money/cars/article-33...

[Bonefish Blues]

WD39 said:

Bonefish Blues said:

Because keep left unless overtaking applies in these zones too.

'Everyone's got themselves into a big damn hurry.' ( Brooks- The Shawshank Redemption.)

It's the law, and a common courtesy. (Me - the living room)

[poing]

I'm clearly becoming more cynical in my old age but having had a quick read of this thread, I didn't read everything fully so might have missed a few details, it doesn't appear a single person here has been caught speeding in one of these zones.

Lots of people have colleagues/friends/pets that claim to have been caught but not a single person here has?

Either we are all exceptionally law abiding or these things take serious speed to set them off.