Speeding through average speed camera zones - What gives?

[Baz Tench]

aero93 said:

Does anyone know anyone that has actually been caught by these?

Yes, I know someone who was done by the ones on the temporary 50 zone which was between Rugby and Northampton until recently.

He did the same kind of speed (60ish) in the temporary 50 between Cannock and Stafford on the M6 and wasn't done.

It's purely a gamble IMO, and for me, not one worth taking.

[Timbola]

How about ... ignore the fact that there are speed cameras and drive at around 50mph anyway, because areas where roadworks are undertaken are dangerous, hazards are more likely, generally with narrower lanes, and workmen may be present.

Anyway, I'm off to shave the goatee and resign my directorship.

[sicasey]

Timbola said:

because areas where roadworks are undertaken are dangerous, hazards are more likely, generally with narrower lanes, and workmen may be present.

No sign of man nor shovel on the M1 last night for many miles.

[dcb]

sicasey said:

This isn't the first time I've witnessed this malarkey but I really need to know, what do they know that I don't?

Averages aren't maximums ?

Doing 70 in a 50 for a short time in a long 50 section might only move the average up 2 mph.

For example, do 45 mph in a 50 and you are fine (as far as being forced to drive slowly
can be construed as safe).

Do 10% of that section at 70 mph and the maths are

0.1 * 70 + 0.9 * 45 = 47.5 mph

so you are still fine and the average has only moved 2.5 mph.


Also, Brit speedos overread. I've been setting my cruise to 60 mph in these sections
(GPS 55 mph) and I'm still waiting for my first ticket.

There is a grey area above the limit. They don't do folks for 51 in a 50 - it wouldn't
be practical policing, although the Brits tend to be pretty docile.

[Palms]

aero93 said:

Does anyone know anyone that has actually been caught by these?

Yes, a freind got caught about a year ago on the m1 northbound sheffied ish, 60 something he got done for!
I used to work with him and he always sped through them claiming they dont work especialy the ones on the m62 towards manchester way (gone now i think) and every day there and back went through at 70 ish and never got a ticket.

So from his experience some do some don't,

[Adam Ansel]

As has been pointed out your speedometer doesn't really say how fast you are going, just an approximation. They usually overstate your speed and a change in tyres can change the accuracy. Try using a satnav that gives a speed read out and compare it with your car speedo!
The ACPO guidance for enforcement is posted speed limit +10% + 2 mph (they deduct these allowances from the stated speed when they send you a speeding summons). So 35 in a 30, 57 in a 50 and 79 in a 70. I have set the cruise to this using accurate satnav speed and gone through laser speed traps with no problems.
The average speed cameras are not very accurate, so give even greater margins of error before prosecuting.
Add together speedo inaccuracy, ACPO allowance and average speed camera margin and it takes a surprisingly high indicated speed to get done.
I don't know if this is still the case but average speed cameras were lane specific. So just switch lanes between cameras and they couldn't measure what you were doing. Hiding behind a truck as you go through a camera, so it can't see your numberplate, will obviously confuse the system.
If you do get caught there is a get out of jail card, just do their speed awareness course and laugh at their brainwashing lies.

[Monkeylegend]

RobM77 said:

Two things spring to mind:

1) Once one driver does it, the others will follow like sheep.

2) For the system to be there it needs to be cost effective. These drivers are paying the bills.

This, every section of average speed cameras has a driver employed by the HA/Police in a plain car whose job it is to drive through at 70, others see this and think it is ok to follow and ker ching...........


Well that's what a man down the pub told me.

[SturdyHSV]

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!

Now I have heard, but only second hand from a colleague who was shown around a control centre that part of the reason is also the way the distance must be measured between the two cameras.

Over a long stretch, or even a very short stretch, which lane somebody drives in could affect the distance travelled quite significantly. If you were intentionally going to the 'inside' lane of every corner travelling at an actual 55mph (so within your 10% + 1 allowance) your route would be a shorter distance and thus your calculated average speed could well be higher than somebody travelling at 56mph who was fastidiously sticking to the 'outside' lane of every corner (not sure why one would do this...)

As such, for the avoidance of doubt and any leg to stand on regarding 'I was changing lanes a lot m'lord' apparently the average speed is calculated based on the actual distance between the two cameras in a straight line. Again, this gives you even more slack in the sort of speeds you could get away with if the road has a lot of corners between camera sites.

As for some of the other points:

Yes, the cameras used to operate in pairs. They would mix the pairs, so not just one after the other, but originally yes, they were lane specific pairs.

This is no longer the case. Your plate is read by any of the cameras, stuck in a database, matched, and the average speed calculated.

A lot of cameras can cover 2 lanes, certainly the ones we sell can go up to 3 from 1 camera, so being in the middle of 2 lanes doesn't matter, you'll still be picked up by the camera, and you'll just be seen as being in whichever lane it happens to resolve you to based on how the operator has set up the lane boundaries.

To the OP:

Your cruise at 52 could have meant an actual speed of ~47mph. Somebody could probably quite merrily drive through certain sections at 60mph and be fine. Then it's a matter of how accurately you're able judge the difference between a car passing you at 13mph (47=>60) and 18mph (52=>70)

Edited by SturdyHSV on Thursday 11th February 09:35

[EazyDuz]

Timbola said:

and workmen may be present.

That part made me laugh

[xRIEx]

dcb said:

Do 10% of that section at 70 mph and the maths are

0.1 * 70 + 0.9 * 45 = 47.5 mph

so you are still fine and the average has only moved 2.5 mph.

Averages of speeds is not always so straightforward. I think if you're talking about 10%/90% of the time taken to travel through the zone, you may be right; if you're talking about travelling 10%/90% of the distance of the measurement then I make the average speed to be 46.667mph.

Taking a distance of 1000m, 900m travelled at 45mph (20.1125m/s) and 100m travelled at 70mph (31.286111m/s).

The 900m at 20.1125m/s is covered in 44.74829s, the 100m is covered in 3.196306, the 1000m is covered in 47.9446s (I've not checked the rounding, just going on what Excel is telling me), so 1000/47.9446 gives an average of 46.6667mph.

As long as I haven't screwed up. Yes I could have done it as a mile and kept the mph units, but I like SI units.

[1Addicted]

During carriageway widening works along the A23(M) last year/year before, the speed limit was set to 40mph and was averagely monitored. I did just that but like you've all said, people fly past, I guess 60mph+.

A few weeks into the works, a digital sign board popped up that gave weekly updates on the number of people caught. It started off in the thousands, then right at the end of the works read around 40 offences. This must mean that most of the drivers were just plain idiots who didn't think the cameras did anything, but when thrown in their face, they paid attention...or got sick of receiving points.

Edited by 1Addicted on Thursday 11th February 10:23

[w1ntermut3]

Not a huge amount to add to the discussion, as both 10% rules and speedo innacuracy have been covered.

A final point worth considering: take your 55-60mph cruise control driver, skirting the limit. He will at some point encounter a bimbo box overtaking another at 45mph. This will then give him some time at 60+ before his average speed breaks the magic 50+10%+2+error.

In reality this happens about once every two minutes on a road like the a1. Hence, blokes doing 70. Because actually, theyre still averaging like 49.

[3xpendable]

Synchromesh said:

Those 52mph lunatics eh? Killing children on empty motorways...

Anyway, since when did PH turn so anti-speeding? You feel good about people getting fines for driving quicker than you, seriously?

Because, as much as we are all petrolheads and dislike them, Speed limits are a LAW. Going 70 through a 50 zone is breaking the law in exactly the same way as assaulting someone, burglary or theft is.

Disagree? Ok well let someone steal your car or break into your home, then see if you 'feel good' about that person getting a fine/prison time for taking your stuff.

[The_Burg]

I know these supposed to be average speed cameras but is there any sort of overide?
For example if you went tearing through at 150mph then slowed down enough to average under the limit would it register anything? I would have though there must be some sort of check.

[1Addicted]

3xpendable said:

Because, as much as we are all petrolheads and dislike them, Speed limits are a LAW. Going 70 through a 50 zone is breaking the law in exactly the same way as assaulting someone, burglary or theft is.

Disagree? Ok well let someone steal your car or break into your home, then see if you 'feel good' about that person getting a fine/prison time for taking your stuff.

I wouldn't really feel the same feeling towards some n0bhead that overtook me at 120mph as I would a "scrote" who burgled my home. Speed limits are the law, you're right, and excess speed in the wrong situation can have catastrophic consequences for someone but, adhere to them most of the time and pick your moments in safer environments to be silly, and you'll be largely ok.

[3xpendable]

1Addicted said:

I wouldn't really feel the same feeling towards some n0bhead that overtook me at 120mph as I would a "scrote" who burgled my home. Speed limits are the law, you're right, and excess speed in the wrong situation can have catastrophic consequences for someone but, adhere to them most of the time and pick your moments in safer environments to be silly, and you'll be largely ok.

I agree, it's an exaggerated comparison and everyone on here has sped at one point or another, but this nonchalant attitude that a lot of people have that speed limits are just an advisory, and ball like an evangelist if they get caught.

I'm often surprised, when I take my weekend car out, that even when I'm driving in a bit of a spirited fashion (accelerating up to the NSL quickly etc), that's how a lot of people drive all the time.

[Roger Irrelevant]

Far Cough said:

Probably a mixture of :
Have no idea how "average" speed cameras work
stupid / belligerent

I do think this accounts for a lot of it. Quite a few times on the A1 towards Scotch Corner I've seen people barreling along at about 70 for a good while then braking down to 50 just before the camera. So they know the cameras are there, they know the limit is 50, they don't want to get caught, they don't have any special knowledge about the cameras, but their lack of understanding of how an average works lets them down.

[1Addicted]

3xpendable said:

I'm often surprised, when I take my weekend car out, that even when I'm driving in a bit of a spirited fashion (accelerating up to the NSL quickly etc), that's how a lot of people drive all the time.

That be Diesel power :-D. Agreed, in seriousness, my brute of a V8 is driven with care comparatively but at least the 2.0TDi drivers can tell their friends that they minced a C63.

[sicasey]

Roger Irrelevant said:

but their lack of understanding of how an average works lets them down.

If a person has no understanding of what an average (average of anything) means, should they really be issued with a driving licence?

[Andy S15]

I find it hard to believe that people paying no attention to an average speed limit purely don't care, are ignorant or unaware of the system. I see far too many people doing it for this to be the case and I don't even drive in average zones that often.