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Thread: SPEED CAMERAS ??? Cash cows
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22nd October 2006, 10:26 PM #31
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22nd October 2006, 11:23 PM #32Senior Member
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Got another one have we?:mad:
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23rd October 2006, 01:04 AM #33Senior Member
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Studley
No worries mate. Here in SA the cameras are not run by SA Police they are run by Police security (contractors).
I wouldn't trust the system either . I would request a camera photo every time.
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23rd October 2006, 01:50 AM #34
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23rd October 2006, 07:48 AM #35
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23rd October 2006, 07:26 PM #36
Hi Niks
Sorry to take so long to get back to you. Just to assure you that I did in fact visit the site lets have a look at the information on speedo error;
(Site info in blue)
(check out the truth in red )
Reasons for Speedometer Error Tolerance
There are sound technical reasons for a car speedometer having a wide tolerance, particularly under ADR 18/02. Unlike the new ADR 18/03 which applies to vehicles registered after 30 June 2006, ADR 18/02 does not provide any test qualifications to its required error tolerance of ±10%, consequently there is no known base calibration point. The factors that influence the accuracy of the speedometer are:
1. Diameter of the tyre.
2. Accuracy of the speedometer sensor.
3. Accuracy of the speedometer indication.
4. Ability to accurately determine the reading on the speedometer dial.
It is important to note that there is a fundamental difference between speed measurement by a device such as police radar and a car speedometer.
DER - They use two methods to achieve the same outcome.
The police radar device is measuring the time taken by an object to move between two points, and within the accuracy of the device, calculates a speed.
No, radar uses the doppler effect to calculate speed which is a change in frequency of radio waves.
The car speedometer is based on an assumption. It typically measures the speed of the rotation of the drive train or wheel and calculates a speed. The assumption is that the tyres are a known circumference. Significant error is introduced into the assumption when the tyre circumference alters due to tyre pressure, tyre wear and load in the car.>>
Summary of Speedo Errors
1. Diameter of the tyre due to tyre wear. >>
New tread depth is 10mm, legal minimum is 1.6mm. Difference of 8.4mm changes the tyre circumference by an average of 2.9%
Any wear is in the favour of the driver because the tyre gets smaller, rotates faster so displays a higher speed on the speedometer 3% No its 2.9% (lets stick to the facts even if they are wrong)
2. Diameter of the tyre due equivalent tyre sizes>>
Alternative tyre sizes of different widths and profiles are permitted to be fitted to the car. These can alter the circumference of the tyre by up to 3%. If the operator chooses to change the tyre from that which is origianal equipment then problem belong to them.
3. Diameter of the tyre due to tyre pressure>>
On a 215/45R17 tyre, altering the tyre pressure from 22psi to 40psi alters the height of the tyre and consequently its circumference .2% yes it gets bigger but who is doing this. The manufacturer sets the recommended tyre pressures and they are displayed on the tyre placard. Stick to the recommended pressure no problems.
4. Diameter of the tyre due to load in the car>>
On a 215/45R17 tyre, with a tyre pressure of 22psi, adding 60kg for a full tank of fuel, 150kg for two adults in the rear seat and 60kg of luggage alters height of the tyre and consequently its circumference. 2% Once again the tyre is smaller, speedo reads higher.
5. Accuracy of the speed sensor on the gearbox>>
Typically a device that measures measures the rotation in the gearbox. It is usually fairly accurate, typically 1 rpm in 1000. ± 0.1%
Who says, who measured this?6. Accuracy of the speedo dial indicator>>
If a specialist Speed Detection Speedo is only accurate to +/- 2 km/h accuracy and displays in 1km/h increments, what makes you think your speedo is equal or better?> ± 3%
Police speedometers are checked for accuracy to within this range so that if you are booked they will write it down by at least this amount which is in the favour of the motorist as it will put them in the right fine bracket.
7. Resolution of the speedo indication>>
The graduations on the speedometer dictate the degree to which the speed can be resolved. ± 2%What does this mean? Graduations are wrong? by 2%? Who measured this?
8. Eye sight, ability for the eyes to focus on the speedometer.>>
It is a medical fact that in people 40 years and over the eye starts to loose it's flexibility due to age and consequently the ability of the eye to rapidly refocus, or to refocus on close objects diminishes. The error will depend on the resolution of the indication and is likely to be twice the width of the speedo needle. ± 2%
I love this one, lets add in old peoples eyesight as a reason. Poor buggers. What about people of asian background, surely we can bring them in on it as some have poor peripheral vision.We could add in people with crooked necks, I am sure there must be an error there.Or perhaps tall people who look down at an angle or short people her have to look up.Or chicks with large breasts, they sloop forward due to the weight so maybe they are too close to see properly.What about a tall, crooked necked, asian, chick with super dooper breasts, must be out by 30%.
TOTAL-There are two errors to summate:absolute errors, such as those due to tyre wear, and the ± error tolerance.>>
Total of the absolute errors (1,3 & 4) is 8%. These give 8% variation in the car speed, independent of instrumentation errors.>>
Total of the tolerance errors (5 & 6) is ±3.1%. This is the accumulated error of the instrumentation.>>
The readers ability to determine the reading (7 & 8) adds another ±4%.Total possible error to determine the speed of the car will be:±7% (or 14% absolute), PLUS the absolute errors in speed of the vehicle of 8%.20% or ± 10%Note: the error due to alternative tyre sizes (2) is not included in the total above. This would increase the total to 23% or ±11.5%.
And here is the really stupid part. Lets make up garbage percentages and add em all up to support a stupid arguement.
See.....told you it was a stupid site.
And just to add in a little life experience in all my time in traffic/accident investigation no one who has complained that there speedo was out took up my offer to take the car to the police approved instrument certifier to have it checked. Not one....you know why.....cause they all lied .
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23rd October 2006, 07:58 PM #37Deceased
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As someone who has to wear spectacles in order to drive ( or do many other things ) my licence is endorsed that it is only valid whilst I'm wearing my correct spectacles.
So my understanding is that if a person's vision deteriorates to the extent quoted at that website they cease automatically to be licensed to drive and as such that argument is invalid.
Peter.
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23rd October 2006, 08:04 PM #38Registered
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All I can think of for a reply is.
The state election is just weeks away.
Al
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23rd October 2006, 10:01 PM #39
maybe its better if you check out the forum caps that are on offer. A foiley might help.
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23rd October 2006, 10:18 PM #40
Mind you it is a fair point that the Australian Standard for Speedos is looser than the tollerances they put on speed cameras. I don't think that website mentioned that.
I was happier when the whole thing was administered by the police and they would pull you over if you were caught in the act.
Getting a notice a few days or a week later you can't really remember or be sure what happened at the time of the alleged incident thus losing your ability to defend yourself.
Personally I am very interested in the placement of cameras and also their calibration, that is the testing of the cameras to see that they are returning an accurate reading. Remember that the speed of sound and light waves varies due to factors such as tempreture humidity etc etc. The angle that the camera faces the oncoming vehicle is an issue too. There is sadly little reporting on this. I don't like the assumption that they work because the manufacturer says so.
StudleyAussie Hardwood Number One
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23rd October 2006, 10:39 PM #41
Dazzler, so eloquently put and well presented, I grade you a distinction. C'mon Niksfee, the silence is deafening!
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23rd October 2006, 10:43 PM #42
I am a bit of a bugger on this one because I reckon it is not revenue raising if you dont get caught. I speed, like most of us, to about 10 km over the limit but no more. If I get caught I cop it on the chin and take it. I cant stand the people who cry like they are little goodie two shoes and go on about it being revenue raising...... bottom line is if you dont want to add to the coffers then dont speed and dont run red lights.
To me it is simple. Sorry if this offends anyone. Not my intention.
PeteIf you are never in over your head how do you know how tall you are?
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24th October 2006, 08:55 AM #43
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24th October 2006, 11:19 AM #44Banned
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24th October 2006, 10:33 PM #45Novice
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The Victorian Premier Steve Bracks stated on radio 3AW when asked if police will operate speed cameras, He replied that the Police will not operate speed cameras as they were given more important jobs such as maintaining LAW and ORDER.
My question is, What is the purpose of speed cameras???
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