Safe Speed Forums

But what, exactly, are you being protected from, hmm? A bit of verbal abuse. If someone is so thin skinned or easily offended that they need to carry a gun or have the support of the local police force to protect themselves against a raised voice and a few choice swear words, then perhaps they're the ones who need to seek professional help.

Remember, we're not talking about being protecting the accident-causing driver from a genuine threat of physical attack, we're talking about an innocent driver, shocked and stunned on the receiving end of someone elses driving mistake, verbally lashing out at the idiot who's just placed their life at risk. Can't you see the difference between this sort of confrontation and one where an ability to perform self-defence (directly through use of personal weaponry, or indirectly through use of a third-party interceding on your behalf) IS genuinely necessary?




I wasn't suggesting we should start shooting at numpty drivers who collide with us because of their incompetence, nor was I suggesting that there might be something personal in an accident. Indeed, even if someones actions are deliberate, that doesn't mean there must be a personal aspect involved as well. But if someone, as a result of their incompetence, causes an accident to occur, it should be treated in a different way to an accident that occurs more, how shall I put it, accidentally. Someone collides with the rear of your car because they weren't paying attention. Someone collides with the rear of your car because their brakes suddenly failed. Are they both the same kind of accident? Not in my book, and if I were the victim in both of these scenarios my feelings towards the driver hitting me in the former would be very different towards the driver hitting me in the latter. Is that wrong?





True, but that doesn't mean the material damage isn't also important. Damaged vehicles can be repaired or replaced, but someone has to pay for that, someone will be inconvenienced by that. If the poor behaviour of another road user cause me financial penalty and/or to expend my time and energy getting my car repaired or replaced, then don't I have a justifiable reason to be angry with them even if no-one was injured?

As far I anyone can tell, these are exactly the same cases - you could not tell the difference if you were hit in this way, so it is best to keep calm until you know.

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I'd have said that an accident is never "intentional". If intentional, it's not "accidental"



Simplistic and flawed logic. Your point has merit subject to the crucial qualification ".... all else being equal". An unintentional collision is not equal to intentional speeding (if the latter results in no harm). I accept there are questions of degree but that underlines the absurdity of your simplistic contention.





Absolute claptrap. You need to get your thinking sorted out and turned right way up. Bad luck is not a necessary component in any crash. Lack of due care almost invariably is. It is true that lack of due care will not always result in a crash but that's a quite different conclusion. Ypu said: "Many crashes don't happen because the bad luck element is missing"? Do you really attribute safe driving and accident avoidance to luck?



More claptrap. So you assert that "the chance of causing an accident" is the same (say): (i) regardless of circumstances?; or (ii) regardless of the nature of the 'offence'?

I'm actually quite intrigued by the emergence of the concept of 'luck' in this thread. I believe that this is the way many people who are involved in incidents look at it, a matter of bad luck.
Even the use of the word 'accident' attracts the insinuation of an element of misfortune in the event; "That's why they are called accidents" I once saw written in a newspaper letter.
IMHO, categorising motor vehicle incidents in this way represents a 'societal acceptance' of the inevitability that circumstances will periodically conspire to create a crash and that drivers themselves are just unlucky if they happen to be involved. I recall very well the time I was rear-ended by a van driver on the A1 and the driver's point blank refusal to accept that, had he left a larger gap betwen us, it could have been avoided. Even the witnesses who stopped to check all was OK, shrugged and put it down to 'one of those things that happens'.
Countering this blithe acceptance of 'bad luck' as a factor in motor vehicle incidents msut sit somewhere high on the list of 'things to be corrected' in the minds of the motoring public.

The flip side of this "bad luck" thing is individual responsibility.

My first responsibility is to not cause a crash.
My second responsibility is to avoid the mistakes of others.

So rather than trying to say: "it's not luck", I think we should be saying: "it's your responsibility". It's more positive, and it goes further.

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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

There seems to be an assumption in there that a "legal sanction" may make careless driving accidents less likely.

I can't really see it myself, unless the legal sanction is enforced training.

I'm not at all sure we have the right assumptions of carelessness in place either. We might well be able to use the law to prevent folk eating their Mars bars, but then I'd be absolutely amazed if eating a Mars bars had ever actually caused a crash. The sorts of carelessness that do lead to crashes are failing to observe adequately and failing to pay attention in general.

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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

What a load of tosh! A driver who is driving perfectly can still have an accident because he has the bad bad luck to be on the road at the same time and place place as a tosser. A driver who is driving attrociously often narrowly avoids crashing (for a long time at least) because of the compensation of others. Until we realise that there are random issues that we have variable degrees of control over (luck, or lack thereof), we will take risks we don't understand by e.g. speeding etc.

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Because there are millions of signs to show the limit, every single car on the road has a speedo and knowledge is tested when you get your licence. I can't believe there are people out there who can't tell the difference between being within the limit and over it. Most are just chancing it, hoping for the best.



No, equally, not more. This is coherent - it is only possible to tell the type of the error (crash error or non-crash error) after a crash has happened, not before, even if the apriori risk assessment of the likelyhood of that specific error causing a crash is identical. It stands to reason, therefore, that the gravity of the offence at the time it is committed (i.e. before a crash or non-crash)is identical whether a crash happens or not, because the perpetrator has no knowledge of whether a crash will happen (drivers are very poor judges of their own abilities). If the gravity of the offence is the same, then the punishment should be the same in my view.

As an analogy, consider this. If I stand in a room with a blind fold and shoot, and someone is hit, I should be punished. If I stand in a room with a blind fold and shoot, and nobody is hit, I should be punished just as much.



If it wasn't gasted before, I bet it is now!

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You're reverting to your trademark qualities of argumentativeness and sophistry, basingwerk. Bad luck is (almost) never a necessary component in accident causation. Obviously a careful driver may become involved in an accident, through no fault of his own, because of bad luck (although better drivers will tend to avoid 'bad luck' through good hazard perception and anticipation).

A classic example of a basingwerk fairy tale analogy:

I'd support enforced training as an alternative legal sanction and agree it could be more effective in reducing such accidents. However, I was aiming at the contrast between the existence of a sanction for speeding (often no safety violation) and (often) none for causing a crash (self-evident safety violation).



Agreed. That's why the mobile phone use law is unnecessary (although I'd concede it may be justified if there was evidence of a statistically significant correlation between mobile use and accidents).

Some of which are incorrectly placed, some of which are badly faded, some of which are missing, some of which are obscured by graffiti, vegetation or other roadside furniture...




I certainly can't tell the difference between 29.9MPH and 30.1MPH. Can you? Neither, being more reasonable about it, can I always tell the difference between 30MPH and 35MPH unless I specifically check my speedo - it's quite possible that whilst driving along trying to remain legal within a 30 limit, inbetween routine speedo checks my speed will have drifted up to a point which would attract the attention of a scamera. And if the scamera in question is capable of catching you before you've had a chance to reduce your speed (i.e. a typical talivan operation), then you're screwed despite the fact that you're trying to comply with the spirit of the law even if, momentarily, you're failing to comply with the letter of the law.




I wonder how many stage magicians/illusionists would still be in business if your version of the legal system were in place...

Speak for yourself, mate . With speedos being up to 10% inaccurate I can't tell the difference even if I do check the damned thing. What most of us can tell, and not with the speedo either, is the difference between too slow (anti-social) and too fast (dangerous). That ought to be enough.

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Make everything as simple as possible, but not simpler - Einstein

Seriously though, comparing the speedo with a GPS receiver suggests it underreads by 1MPH in the 30-40MPH region, with a gradual increase in error up to 3MPH under in the 70-"I don't really drive this fast on the motorway" region. So yeah, speaking for myself, I know I can tell the difference on my present car. But as you say...



...precisely. Back in the days when my girlfriend used to drive a minicab around London, she spent a few months driving with a knackered speedo. How many accidents did she have during this time. None. As she said, she didn't need to know her exact speed in order to drive safely, and this was sufficiently long ago such that she didn't need to know her exact speed in order to avoid being scammed - she was able to judge her approximate speed with sufficient accuracy not to attract the attention of the trafpol patrols that handled speed enforcement in those days.


I wonder if all the people so in favour of rigidly enforcing speed limits have ever stopped to consider

...when driving along a residential street with cars parked both sides of the road, do they need to check their speedo in order to select an appropriate speed?

...when approaching a slower moving or stationary vehicle, do they need to check their speedo in order to determine when to start braking?

... when approaching a bend, do they need to check their speedo to select a safe speed to negotiate the bend?

...when driving in conditions of poor visibility, do they need to check their speedo to select an appropriate speed?

Know exactly what you mean. I know someone who drove with a bust speedo for a few months. Collisions... zero. Surprise, surprise. BUT, one NIP costing forty quid after being pinged but some plod hiding in a bush at arse o'clock in the morning. Straight up!

While we're on the topic, I'm sure cars once had the rev counter as the most prominent instrument. Am I right in thinking that not all actually had speedos? If so, are such cars still road legal?

Edit: Damn, I'm always doing this. Thinking of something else a nanosecond after clicking the submit button. Anyhow, another point about speedos... if they're such a big deal why are they not tested for accuracy as part of the MOT? Yes, they check to see if it works, at least i think they do. But they don't test to see if it's actually compliant do they? Can speedos get even more inaccurate with age?

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Make everything as simple as possible, but not simpler - Einstein

That would be going back a very long way. Apart from sports cars and a few top-of-the-range models, in the post-war era the vast majority of British cars didn't have rev counters. It's only in the past ten or fifteen years that they have become standard on pretty much all cars.

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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

It depends on the principle of operation employed by the instrument. Some instruments are absolutely accurate. For example, if the speedo uses a toothed or notched wheel and a light or magnetic sensor to directly sense wheel rotations, that would be an absolute measurement, without error. However, it is changed into an approximate speed by factoring in the circumference of the wheel. As tyre pressure and depth, profiles etc change over time, even an absolutely accurate instrument may not give an absolutely accurate measurement of a derived variable. However, such instruments are quite good – typically, accurate to a percent or two when calibrated against a certain tyre size and profile, drifting off over time as the tyre changes, and much less accurate when different tyres or wheels are used. In general, wear makes the instrument read higher than it should, because the car travels less far per revolution. This is a good thing (from my point of view) because it makes drivers drive more slowly as their tyres wear. Other principles of operation (e.g. magnetic field drag) etc. may not be absolute and would have an intrinsic error, as well as the additional error from the derived variable.

It is no use pinging everybody at exactly 30 mph or more. Some reasonable margin for error must be allowed for instrument discrepancies (at both the camera and the speedo, which can be cancelling or accumulative depending on your luck) and for momentary lapses. It is no use pinging everybody in the same way once they have exceed their reasonable margin, unless you want to piss everybody off – small offences should get light treatment. Heavy offences - throw the book at them, and if they loose their license, good riddance to old rubbish.

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Ifthe data so derived then stays in the digital domain and there are no "missing pulse" type errors, then you are correct.

However in most vehicles the signals you identify are returned to the analogue domain involving a digital to analogue converter with it's own calibration, then fed to a moving coil meter for display involving another two layers of calibration (movement and scale).

And we shouldn't forget that vehicles are supplied with different rear axle ratios and a method is provided to match speedo calibration to rear axle calibration. This may be a coding plug, a dipswitch or a different insurument. The possibility exists that the car we're examining has had the wrong coding plug fitted.

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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'd heard somewhere before that magnets were involved. I can see how tyre pressures and condition would affect accuracy, but I was wondering if there was anything in the speedo itself, such as the magnet(s) that could alter over time.

Congratulations, you're becoming a petrolhead. One more of us and one less of them.

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Make everything as simple as possible, but not simpler - Einstein

There at several ways that magnets can be used. First, in very simple speedos, I think the principle of operation is that a bar magnet rotates inside a drum that is free to turn. The magnetic flux imparts a torque onto the drum and turns it. The pointer of the speedo is attached to the spindle of the drum, and a light spring provides an opposing force to return the pointer. This is not an absolute measurement, and would be subject to several sources of error such as variations on the strength of the magnet, friction, temperature, the spring etc. These would vary as the system ages. In another scenario, a magnet is attached to a wheel that spins proportionately to the speed on the wheel. This magnet triggers a sensor on each revolution. By integrating the number of turns over a period of time, the exact speed can be found. This is an absolute measurement, but is subject to error due to the variability of the wheel’s circumference, and also, as SafeSpeed points out, due to any analog conversions when transmitting the value to the display. A digital display or an analog display with servo feedback and graycode positioning could give a true reading.



Give you an inch, and you take a mile!

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Blimey, I haven't come across Gray Code for about 20 years!

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CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!