Safe Speed Forums

We're told that they're independent, but I wonder how independent they actually are.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

Considering that the white lines are, as I understand it 'worth' 5mph each (line and space) - we might deduce that he is going approx 25mph ...

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

I checked, double checked and triple checked using Google Maps and the regs ("traffic signs manual"): the repeat distance on this road appears to be 2m.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

That was a oscillator module, not a crystal http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=535-9321-6-ND. And the price is <$2 for one offs. I don't do mass production - all my products are lovingly hand crafted

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

agree with the elec techies (and weepee).. this is such a non issue... if the electronics is up the duff they still have the photos (i thought that was the whole point), and they say...?

he's just trying for a novel technical get out.

Well in that case then and looking at your figures that makes each line 'worth' 8.95mph so he is over 40mph ... (thanks)

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Safe Speed for Intelligent Road Safety through proper research, experience & guidance.

...but the timing of the photos is controlled by the electronic-trickery, and if the delay wasn't (exactly) 0.5 seconds, how far he travelled along the fixed markings could not be used to calculate his speed.

Indeed the (earlier) photos do not appear to have a "timeline" - the second flash just has "0.5 sec." and not the (or any) absolute time.

Wasn't there some chappy a few years ago who measured the flash delay of GATSOs and found that they were well outside the supposedly calibrated 0.5 second gap - in such a way that the "calculated" speed would always be greater??

mb

You're thinking of David Edgar - he claimed 630ms. His website: notsoaccurate.com is now completely offline.
He was found to be a "vexatious litigant", and he IIRC let down a few people.
A Safe Speed page on it.

I don't know what eventually came of this.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

Taken in isolation, the fact that the flashes are 630mS apart rather than the advertised 500mS proves nothing. Do we know that the photographs are taken exactly in synchronisation with the flash - the flash duration could be much longer than the exposure time with the exposure being made later in the first flash than in the second. Also the speed can still be calculated accurately provided the time between exposures is know, whether it be 300mS or 700mS.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

I strongly disagree.

The flash duration is very short; a typical one is about 1 milli-second. It is possible to have an exposure time longer than the flash (most 'point and shoot' cameras are limited to that mode of operation).

The vehicle wasn't blurred in the slightest (especially at the top sections of the wheels which would be 'going faster' than then the vehicle), hence it would support the notion that the flash duration was indeed very short (compared to the delay time anyway).

The relative total darkness of the surroundings in this case indicates the flash was the dominant/only source of light throughout both exposures (I'm sure you know about the 'inverse square' law of illumination) - the ambient contribution of the exposures from front curtain (shutter open) to the rear curtain (shutter closed), is clearly insignificant compared to the flash. The time of the flash is what shows the position of the car; the duration of exposure cannot have had any impact (in this case anyway).

Therefore, the time between the flashes are the critical measure, not the exposures.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

Naturally, on this topic, I humbly bow to your superior knowledge. Could you bring that knowledge to bear my other point - that the actual time between exposures is not critical so long as it is accurately known.

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When I see an adult on a bicycle, I do not despair for the future of the human race. H.G. Wells
When I see a youth in a motor car I do d.c.brown

This is a basic time over distance measurement. This is straightforward to determine for this case given that the distance, and the (relative, not necessarily absolute) time over that distance, is (supposedly) known.
So yes, 'the actual time between exposures is not critical so long as it is accurately known' (and the distance is too)

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

That's the fella!

ISTR that calibration lines were tarmac-ed over, he was forced to change ISP (the old one was leant on?), his bank account was "frozen" and he was forcibly arrested by two thugs^H^H^H^H^Hofficers during which he had a heart attack!!

He might have been somewhat eccentric, but the way that he appeared to be "closed down" must ring alarm bells!!

Maybe the authorities really do have something to hide!

mb

The gatso manual says that the control unit has a temperature range of -20° to +60°. It doesn't mention temperature ranges for any other modules, nor does it suggest that it monitors the temperature or shuts down if it falls outside this range. (RedSpeed equipment apparently does this.)

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Andrew.

It is a condition of type approval that it shuts down when the temperature is too low:

My laptop has a specification which states that the battery will last 2 to 3 hours under normal conditions.
It doesn't.
Manufacturers claims should be put to the test if below the Home Office type approval tests!
There were several days this winter when the temperature was below the -10°C here in Cumbria and in the Highlands.

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Time to take responsibility for our actions.. and don't be afraid of speaking out!

I'm with you Steve, (like I could go head-to-head on electronics), although I'd like to say is it okay if the two old fogies here, me and Botach , still think of it as a condenser?

I feel like a 1pf ceramic amongst you 1000uf electrolytics

Although at least it means I can swing both ways without blowing my top.

Yeah ok, I went too far with the analogy...

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The views expressed in this post are personal opinions and do not necessarily represent the views of Safe Speed.
You will be branded a threat to society by going over a speed limit where it is safe to do so, and suffer the consequences of your actions in a way criminals do not, more so than someone who is a real threat to our society.

ooops! there you go with your assumptions again. the speedmeter handbook doesn't set conditions of type approval, only requirements to gain type approval. Conditions are something quite different and this is not a condition.

Giving your age away, eh Tone?

Mind you, the capacitor across the points on a car (the ones which still have them) is still known as a 'condenser'

Just as long as you still have the capacity for life

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

An interesting side note...it's amazing how many people on this site have a background in electronics/electrical engineering of some sort....I know when i worked at Decca, in the early 70s, the majority of engineers there were interested in cars, rallying etc and yet friends from other occupations didn't show as much interest...very interesting!!!

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

A distinction without a difference?

Let's try it your way:

Are you happy now GS?

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign