This is also a subject of interest to me, mainly due to the high number of idiot drivers (in my vieew). I have used GPS to "calibrate" my car speedo, which generally under-reads by 5 - 6 Km/Hr at 100 and 110 Km/Hr (the difference at 100 and 110 is not worth worrying about).
The car is a 2004 Falcon Future Wagon.
I am of the view that people (generally) view the car speedo as reasonably accurate, add a few kilometers/hour to make up the correction and add a few more kilometers/Hr to account for the accuracy of the "radar" gun. Therefore if I drive at 110 Km/Hr (where legal in South Australia), it's like I am going the other way - every one passes me, trucks, P-platers etc etc.
If thats not the answer, I suggest its that no one want to be last. I drive, from Adelaide, to either Waikerie or Balaklava each weekend. The nuber of people who come from no-where to sit just in front of me (almost so I am then tail-gating) is amazing.
I woould be pleased to hear the outcome of your deliberations.
John Hudson.
----- Original Message ----- From: "Allan Armistead" <[EMAIL PROTECTED]>
To: "Discussion of issues relating to Soaring in Australia." <aus-soaring@lists.internode.on.net>
Sent: Tuesday, May 17, 2005 2:22 PM
Subject: [Aus-soaring] Off topic - speedo accuracy
I'd like to ask for the indulgence of the group to go a bit off topic to gliding.
Those of you who are also members of NRMA might have seen a letter (and editorial comment) in their last edition about speedo accuracy.
As it relates to an area of interest of mine (roads/road safety) I'm intending to respond on the matter and thought it would be useful to do a straw poll of people who have the ability to "calibrate" their speedos, to get a reasonable idea of the order of accuracy across a range of makes and models. I know both my cars are optimistic by around 6-8km/h at highway speeds.
So who better to ask than people who have access to speed measuring equipment (GPS) and drive a range of vehicles on the highways and byways (glider pilots).
If anyone is interested in giving me some input into this, I would ask you to do the following - safely, on a quiet road, at legal speeds and with a passenger to read the GPS;
. drive at steady speeds of 80, 100 and (if possible/legal) 110km/h as indicated on your vehicle speedo,
. note the GPS reading at each of these indicated speeds
. tabulate the results, together with the make, model and year model of the
vehicle,
. email them direct to me at [EMAIL PROTECTED] (please do not clog up the newsgroup with the results)
Apart from my specific interest in the matter, it is useful information to
have for your own purposes. Australian Design Rules require a speedo
accuracy of +-10%. My experience/observation is that speedos are generally a
bit optimistic, but it is quite possible that if you are reading 100km/h you
are actually doing somewhere between 90 and 110 - which could be important
to know if you are in Victoria with it's 3km/h tolerance level.
Allan Armistead ph (02) 6249 6470, fax (02) 6249 6555, mobile 0413 013 911 PO Box 908, Dickson ACT 2602, Australia
"When once you have tasted flight, you will always walk with your eyes turned skyward, for there you have been and there you always will be." Leonardo da Vinci, 1452-1519
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