handyandy
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| posted on 26/2/09 at 11:47 PM |
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how accurate
just a thought,
was driving my van today using my garmin sat nav,
the speedo on dash said 30mph but sat nav said i was doing 26mph,
speedo on dash said 70mph
sat nav says 62mph
which one is more accurate & so does that explain why when doing "30" it feels so bl@@dy slow ???
andy
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dinosaurjuice
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| posted on 26/2/09 at 11:49 PM |
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its fairly common for car speedos to read over the actual speed. my picasso reads 70 when tomtom says 64. only accurate if travelling on a straight
road and not on an incline.
edit: i reckon the satnavs are more accurate
[Edited on 26/2/09 by dinosaurjuice]
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Hellfire
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| posted on 26/2/09 at 11:54 PM |
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SATNAV is correct.... speedo's are allowed to read 10% over, so they often do.
That's how come the Chav's Corsa does 0-60 in 6 seconds... with his big wheels he's only actually doing 40  Well maybe.... 
Steve
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handyandy
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| posted on 27/2/09 at 12:13 AM |
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makes one wonder then what????? posh voice.
if we,re all driving at 10% below the speed limit why are so many caught speeding, & then me thinks what speed are speed cameras set to catch
speeding drivers?????
its late & my minds wandering
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UncleFista
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| posted on 27/2/09 at 02:32 AM |
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I worked out that under the guidelines (which is 10% +2mph before prosecution here in West Yorks) along with my speedo over-reading by 8% I'd
have to be doing an indicated 50-odd mph to be caught by a speed camera in a 40 zone.
So my question is, why do soooo many people slow down to 25-30 for a 40 ? 
[Edited on 27/2/09 by UncleFista]
[Edited on 27/2/09 by UncleFista]
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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iank
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| posted on 27/2/09 at 06:33 AM |
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quote:
Originally posted by UncleFista
I worked out that under the guidelines (which is 10% +2mph before prosecution here in West Yorks) along with my speedo over-reading by 8% I'd
have to be doing an indicated 54mph to be caught by a speed camera in a 40 zone.
So my question is, why do soooo many people slow down to 25-30 for a 40 ?
[Edited on 27/2/09 by UncleFista]
Surely that's 49.68mph indicated on the speedo using those figures?
Speedo can read up to 10% over but must never read under, so manufacturers will always err on the side of reading 5% or more over to avoid getting
themselves sued.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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ReMan
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| posted on 27/2/09 at 08:20 AM |
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quote:
Originally posted by UncleFista
I worked out that under the guidelines (which is 10% +2mph before prosecution here in West Yorks) along with my speedo over-reading by 8% I'd
have to be doing an indicated 54mph to be caught by a speed camera in a 40 zone.
So my question is, why do soooo many people slow down to 25-30 for a 40 ?
[Edited on 27/2/09 by UncleFista]
Because 40 is the maximum speed, not the minimum speed? And there are speed scameras everywhere!
No I'm not saying I do' and I think your calculation may have saved me from quite a few tickets
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02GF74
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| posted on 27/2/09 at 08:28 AM |
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yep - most speedo overread by quite a fair bit.
My speedo is programmed to read a couple of percent over and it is quite noticeable that traffic that would normally drive a 50 or 60 (in the average
speed camera lanes) does a fair bit under that. In the tin top it would be a tad over.
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BenB
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| posted on 27/2/09 at 08:54 AM |
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Yup. Speedos can over-read by 10% but cannot under-read even by 0.1% so up to 10% is not unusual. It does vary though, my Megane is almost spot-on
(about 1% high).....
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David Jenkins
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| posted on 27/2/09 at 09:07 AM |
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I believe that the speed is +/- 0.1 mph if the satnav can get a signal from enough satellites.
In my Yaris, that means that 70mph on the satnav equals 76mph on the car's speedo. When I'm using the satnav I usually drive at more than
70 on the speedo but less than 70 on the satnav - this means that I'm going fast enough, with a reasonable margin of safety for all the speed
cameras.
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UncleFista
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| posted on 27/2/09 at 10:23 AM |
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quote:
Originally posted by ReMan
Because 40 is the maximum speed, not the minimum speed? And there are speed scameras everywhere!
No I'm not saying I do' and I think your calculation may have saved me from quite a few tickets
I'm not arguing with that, but I'm annoyed with the people who bimble along at 40-50 in a 40, then when they spot a scamera they
immediately drop down to 25mph and crawl through the scamera trap....
It makes no SENSE I tell ya ! 
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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handyandy
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| posted on 27/2/09 at 10:34 AM |
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quote:
Originally posted by UncleFista
quote:
Originally posted by ReMan
Because 40 is the maximum speed, not the minimum speed? And there are speed scameras everywhere!
No I'm not saying I do' and I think your calculation may have saved me from quite a few tickets
I'm not arguing with that, but I'm annoyed with the people who bimble along at 40-50 in a 40, then when they spot a scamera they
immediately drop down to 25mph and crawl through the scamera trap....
It makes no SENSE I tell ya !
totally with you on that point,
so in a way it shows two things really,
drivers are happy to travel at 40 to 50 in a 40 zone but then don,t trust their speedo when going past a speed camera,
and secondly
its shows that most drivers are not aware what a given speed feels like without looking at the speedo.
as when driving / riding on a track the sense of speed is generally lost as no white lines , lamp posts etc to give the effect of speed & usually
you don,t realise how fast you are actually driving????
if that makes sense?
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iank
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| posted on 27/2/09 at 10:41 AM |
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quote:
Originally posted by handyandy
quote:
Originally posted by UncleFista
quote:
Originally posted by ReMan
Because 40 is the maximum speed, not the minimum speed? And there are speed scameras everywhere!
No I'm not saying I do' and I think your calculation may have saved me from quite a few tickets
I'm not arguing with that, but I'm annoyed with the people who bimble along at 40-50 in a 40, then when they spot a scamera they
immediately drop down to 25mph and crawl through the scamera trap....
It makes no SENSE I tell ya !
totally with you on that point,
so in a way it shows two things really,
drivers are happy to travel at 40 to 50 in a 40 zone but then don,t trust their speedo when going past a speed camera,
and secondly
its shows that most drivers are not aware what a given speed feels like without looking at the speedo.
as when driving / riding on a track the sense of speed is generally lost as no white lines , lamp posts etc to give the effect of speed & usually
you don,t realise how fast you are actually driving????
if that makes sense?
Actually I believe it's more to do with the fact that there are generally no speed markings just before a camera to let you know what the area
you're in is limited to so people assume 30mph to be "safe" even if the stream of traffic has correctly been doing 40mph.
I believe the camera should have a speed sign associated with it with a clear indication of the limit (none of those white rounds with black lines -
if it's 40mph say 40, if it's 50 have a 50 sign).
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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David Jenkins
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| posted on 27/2/09 at 10:50 AM |
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I've mentioned the French speed traps here before: The fixed ones have a HUGE sign a few hundred metres before, with the speed limit marked on
it. Quite often the speed limit is also written on the road. In one place they had rumble strips to make sure you notice! The actual radar is
usually very hard to see, but in all fairness, if you manage to get a ticket from one of those you deserve a white stick, dark glasses and a guide
dog!
As for slowing down for speed cameras - I was driving along the A14 last Sunday, doing exactly 70mph (satnav speed). A car overtook me doing ~80, saw
the camera, pulled in front of me and immediately slowed to 60. After managing to avoid his rear bumper, I gave him the customary fanfare and light
show... a mile or two later he overtook me doing ~80 again! Plonker.
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adithorp
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| posted on 27/2/09 at 10:52 AM |
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quote:
Originally posted by Hellfire
That's how come the Chav's Corsa does 0-60 in 6 seconds... with his big wheels he's only actually doing 40 Well maybe....
Steve
Isn't that the wrong way around? With bigger wheels they travel faster relative to what the speedo reads.
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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ReMan
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| posted on 27/2/09 at 01:03 PM |
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quote:
Originally posted by iank
quote:
Originally posted by handyandy
quote:
Originally posted by UncleFista
quote:
Originally posted by ReMan
Because 40 is the maximum speed, not the minimum speed? And there are speed scameras everywhere!
No I'm not saying I do' and I think your calculation may have saved me from quite a few tickets
I'm not arguing with that, but I'm annoyed with the people who bimble along at 40-50 in a 40, then when they spot a scamera they
immediately drop down to 25mph and crawl through the scamera trap....
It makes no SENSE I tell ya !
totally with you on that point,
so in a way it shows two things really,
drivers are happy to travel at 40 to 50 in a 40 zone but then don,t trust their speedo when going past a speed camera,
and secondly
its shows that most drivers are not aware what a given speed feels like without looking at the speedo.
as when driving / riding on a track the sense of speed is generally lost as no white lines , lamp posts etc to give the effect of speed & usually
you don,t realise how fast you are actually driving????
if that makes sense?
Actually I believe it's more to do with the fact that there are generally no speed markings just before a camera to let you know what the area
you're in is limited to so people assume 30mph to be "safe" even if the stream of traffic has correctly been doing 40mph.
I believe the camera should have a speed sign associated with it with a clear indication of the limit (none of those white rounds with black lines -
if it's 40mph say 40, if it's 50 have a 50 sign).
I was definatly not preaching holier than thou! I agree with your point
As far as the cameras, I think that not only should they have a sign asociated, they should have the sign showing on thier "clearly visible
,dayglow frikin boxes to stop people dropping to as you say 20mph
It's just the same as the 3 lanes of cars that womn't pass motoway police as they suddenly cant do more than 60!
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BenB
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| posted on 27/2/09 at 01:16 PM |
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I totally agree that most drivers slam on the anchors to 30mph because it's often quite difficult to know what the speed limit is on a
particular bit of road.
To be honest, that's what I probably use my satnav mostly for!!!!
If the police / councils put up road signs to inform people that they're driving too fast rather than people only finding out retrospectively
when a speeding fine comes through the letter boxes there would probably be less "speed related crashes".....
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