Safe Speed Forums

Following listening to some very depressing nonsense on parliament TV today where they had the second reading of the Road Safety Bill, I've been wondering...

Just how much precision would they like to have to enforce speed limits? And what are the controlling factors?

At present the enforcement limit is "+10% +2mph". This is a pretty sensible interpretation of the risk of accumulated errors.

But what about safety limits? What about social acceptability? What about practicallity? Where would they like to draw the line?

It seems to me that there's a fundamental law of diminishing returns - the more precise we make speed limit enforcement the more driver attention is required to comply.

At some point the risk caused by excessive driver attention MUST cross over with the risk caused by the speed they're seeking to moderate.

Maybe the entire argument boils down to the location of this crossover point? I presume that we could work towards defining an "average" cross over point, as well as a range of practical crossover points.

We've always talked about IF driver too much driver attention is consumed. But perhaps it should be a question of WHEN too much driver attention is consumed?

This might be a little incomplete. I've got something nagging at me that there's a missing element. Any thoughts? Am I onto something?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

BBC 6pm news report stated the 2 pt penalty would be imposed at 31mph, I hope they've misinterpreted the position, for the sake of the average PC on the beat

I personally think the vast majority of Police(persons) do a superb job; it's a shame they get the blame for the antics of the Scammers.

Refer to the latest posts on CSCP to see how wrong it's gone for them...

If it is going to be enforced at such a ludicrous low threshold then the SCPs are going to have to make damn sure every single camera is calibrated correctly and every single mobile operator checks their laser gun before each shift etc etc as the opportunity for fighting over 1 mph is enough doubt to throw out pretty much every single speeding ticket one mph over.

The 10% +2mph is much better.

Alternatively limits can be raised by 10 mph in urban areas and all NSL roads raised to 70. All the other fiddly limits should be removed so we have 40, 70 & 80 for motorways. People then could be reminded that the should be travelling slower than 40 in urban areas but they won't get prosecuted until they go over that limit. 30 will then only apply to those places with the daft 20 mph limits.

This is something we've debated before both here and on other forums. Personally I didn't see anything in the consultation document about graduated speeding penalties that said the existing ACPO guidelines would be scrapped or amended. It simply doesn't mention the subject at all.

Others whose opinions I respect have interpreted it differently.

Of course 31 mph in a 30 has always technically been illegal anyway.

Perhaps someone should ask the DfT.

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"Show me someone who says that they have never exceeded a speed limit, and I'll show you a liar, or a menace." (Austin Williams - Director, Transport Research Group)

Any views expressed in this post are personal opinions and may not represent the views of Safe Speed

The DfT aren't saying. At present they are trying to get enabling legislation through Parliament WITHOUT making any such definition. I think the idea is that the legislation devolves the power to create and amend the penalties and thresholds table to the Secretary of State. There's quite a bit of this going on. I preseum if the Government didn't have such a strong majority they wouldn't be able to get away with it.

Actually it's outrageous. MPs simply don't know what they are voting for.

It was the same with that damn "victim levy". The legislation doesn't mention the level of the victim levy. That gets set later. Frankly I don't see how anyone can vote for legislation like that.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

I had an interesting discussion about this with someone a while back. We were discussing what would happen if an infallible, highly-accurate, omniscient system of detecting every single speeding offence was invented and put into every day use.

This theoretical device could detect any speeding offence, no matter how minor, and does so to the smallest measurable unit of accuracy. Since speeding is an absolute offence, 30.0001mph in a 30mph limit is as illegal as 70mph would be. The device immediately adds points onto the driver's licence, takes their £60 and allows them on their merry way.

If such a 'perfect' device existed, would it reduce road traffic accidents? What level would the prosecution threshold be set to? If set at a miniscule percentage above the limit, how many people would be banned on their first journey?

And so on... :p

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Carl Prescott

Probably 95% of the entire driving population?

Your post represents the reasoning for the unarguable conclusion that the speed limit, in itself, doesn't define the boundary between that which is is 'lawful' and that which is 'unlawful'. That boundary is necessarily defined by the scope and scale of speed detection and enforcement activity. The introduction of automatic detection and fast-track enforcement has re-defined that boundary with the nonsensical result that unprecedented and growing numbers of law-abiding motorists are being turned into serious criminals.

Few understand the difference between 'precision' and 'accuracy' and most lawyers and politicians freely interchange them.

The VASCAR devices have a manufacturer's stated +/- 2% accuracy but a precision 100 times greater. Which makes a reported speed of 100.01 mile/h inappropriate. The speed SHOULD be reported as 100 +/- 2 mile/h and no higher infernce than 98 mile/h should be drawn from the example given.

The objectionable and non-technical expert witness for LaserTech, Frank Garrett, makes claims that his import agencies American product is 100%; they are clearly absurd. But courts and legal people accept this uncritically. In practice under certain circumstances the LTI20-20 is quite accurate, probably better than +/- 0.5%. In others it is quite a lot less and has been demonstrated to be so.

Its Precision is +/- 1 mile/h. No more and no less. It does not read in decimals; it only reports speed to whole mile/h. Its internal algorithm's are claimed to be proprietary ( Garett would not know what an algorithm was if one smacked him in the teeth !)

It would be reasonable to argue that should a charge of speeding at 31 mile/h be brought with an LTI, it could well round up the speed + in accuracy and the motorist could have actually been travelling at any speed between 29.85 and 31.15 mile/h

In English "precision" and "accuracy" are pretty much interchangeable.

Here are the Oxford English Dictionary definitions:

precision

1 The cutting off of one thing from another; esp. the mental separation of a fact or idea. Also (rare), a precise definition.

2 The fact, condition, or quality of being precise; exactness, definiteness; distinctness, accuracy. M18.
2b Statistics. (A quantity expressing) the reproducibility of a measurement or numerical result. L19.
2c The degree of refinement in measurement or specification, esp. as represented by the number of digits given.
2d The accuracy of an act of information retrieval, expressed as the proportion of the retrieved items that are relevant or desired.

2 T. H. HUXLEY The precision of statement which..distinguishes science from common information.


accuracy

1 The state of being accurate; precision, correctness.

2 The degree of refinement in measurement or specification, as given by the extent of conformity with a standard or true value.


"Precision" has an additional technical definition in mathematics (often as "numerical precision"). This is no more than a useful subset of the meaning of the word.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Richard C has a good point. I remember a famous case where a documentary said that the height of Lima was 341 m above sea level (or some such value), clearly an unreasonable level of precision! What they had done was taken a value of 1000 ft and converted it to metres, without thinking about it enough.

[quote="kendalian"]BBC 6pm news report stated the 2 pt penalty would be imposed at 31mph,quote]

That is OK, when they start producing a Speedometer that works to such a tolerance. Then they need to enforce manufacturers tyre recomendations, as soon as we fit differant tyres, we change the calculation that is being made by the speedo.

Tyre revolution / distance covered x axle revolutions x speedo cable turns (or number pulses) = Speed being travelled. All of which carry tolerances, reaching outside of 31 mph

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Steve

As i've made clear before, i am not a traffic Officer. BUT, NO Copper, however anal, will give you points for doing 1mph over the limit, whatever 'they' may tell us to do....

Remember, the PC 'on the beat' or on routine patrol will have no interest in traffic as long as nobody draws attention to themselves by driving like an idiot. We also have no way of accurately measuring speed. I have never been shown how to operate a laser gun, it's nothing to do with me!!!....

Yes, my vehicle (BMW 530) has a calibrated speedo,but thats all, and as i've also stated before, in seven years of policing i've never reported someone for speeding.

As for the gatso limits, well that's another matter....

Agreed - our Man!

As mentioned in the past - we operate a camera van and we usually give a fair margin - 10% plus 5 and patrols use discretionary powers as well.

Common sense has to prevail and we would end up placing everyone under house arrest if we prosecuted for each and every little imperfection - as we do not have enough jails.

Think most of us would just hand in badges if they told us to be daft lads to that extent - the public would not stand for it either.

Have enough problems over speed cam backlash - and we don't even have them as such around here.

Amen to that Brother!!!