I cannot find it ATM but I recall a case a few years ago where a speeding ticket was cancelled because the guy had a very sophisticated GPS set up in his car that showed his speed that was less than the speed he was prosecuted for. ISTR the kit was part of R&D for a SatNav company.
I thought speed cameras were bullet proof (at least the Gatsos) but it might have been out of calibration.
Found it, it was not a Gatso:-)
I was undertaken last winter. It was dark, drizzling and the motorway was very quiet. I had my parents in the car and was doing just under 70. I saw something in lane one, indicated and then moved over to lane 2. The tosser belting it down lane 2 decided to teach me a lesson for using the middle lane and decided to put his main beams on and undertake me. I pissed myself laughing when he hit the set of ladders lying in lane 1 that I had avoided.
I have a vague recollection of the period following the 50 mph fuel saving limit when that was the case.
I work on the assumption that it is usually best to know your enemy so from time to time I have purchased another Highway Code. The first one(s) have long gone (possibly thrown out when I last moved in 1978) but I still have codes with copyright dates 1978, 1993, 2004 and 2007.
On the original subject of gps accuracy in-car sat navs don't seem to come with much (any?) technical information but the handbook for my handheld claims velocity accuracy of "0.05 meter/sec steady state" which is approximately 0.1 mph and near enough dead accurate as makes no difference.
There's one stretch of the A46 where it's noticably annoying, I'm usually tootling along at an accurate 70 on the cruise control, with people overtaking me for the preceeding couple of miles, yet almost every time I end up having to brake because a handful of them panic when they reach the camera.
I will admit that I didn't know for many years that 40 was the limit for HGVs, probably dating back from times when fewer of them obeyed it than now.
I suppose I've flicked through it when friends' offspring have reached driving age and tend to have a copy lurking on the side in the kitchen or wherever.
Similarly with my Nokia 5800 Ovi Maps satnav. When I am using it as satnav - I have to keep it plugged in or the phone battery will flatten in about an hour.
The problem for the manufacturers is the EU regulations on speedo accuracy. In the States, the regulations say that speedometers must be accurate to within + or - 5%. As a result, most speedos made for the US market are very accurate.
The EU regulations state that speedos can over-read up to 10% - but cannot under-read at all. For this reason, cars manufactured for EU use have speedos set to over-read by around 5%. If they tried to make them wholly accurate - then there would be a danger of a 'slightly out' speedo under-reading - and that would be illegal. Manufacturers therefore err on the side of safety by making their speedos over-read.
2007 is the latest. But in any case, no need to buy...
And also requires regular checking and recalibration to ensure continued accuracy...
+1.
Probably an indication of 9 points on their licences:-)
I find a speed limit repeater sign in the camera approach a very good idea.
A wise move. Occasional forays into London are now a bit worrying.
regards
A handy cop-out from the CPS:-
"The officer who operated the camera has since retired.
Without his verbal evidence, we could not prove the case to the required standard."
They've been known to "lose" the video evidence in speeding cases, too, if a driver asks to see it pending an appearance in court.
Only at 30 mph.
Tyre wear or the wrong inflation will only make it over-read more. So there's still no reason not to make it far more accurate when everything is correct. Especially since examples of the same car model will all have near enough the same error...
Assuming you fit the correct size tyres, any error between brands or due to wear or inflation etc is much smaller than the 10% allowed by law. A law which came in when speedos were incredibly crude devices.
FFS, they've been making clocks with a better than 10% accuracy for centuries...
You actually mean worn tyres can make a 3% difference? ;-) But in any case worn tyres just add to the allowable error.
Err, why is that a reason? If they can reliably make speedos which over-read by 5%, why not 4,3,2,1 or 0%?
The fact is some makers fit accurate speedos, some make use of the tolerance allowed by law as a deliberate act.
No analogue speedo will ever be 100% at all speeds as parallax errors will come into play when reading it.
And it's almost always a small solid device that protrudes from the computer case, rather than (like, say, a printer) attaching by a lead.
necessarily that of presenting accurate information. The manual warns of several possible failure modes of the Distronic Plus, one of which is approaching a stationary car too fast. It will only apply up to 40% braking automatically, but it will warn the driver if there is a risk of collision and harder braking is required. Obviously, that does not work too well in a driverless car, as in the video. While it will try to avoid a collision, the main point of the system is to ensure that any accident happens slowly enough to be survivable.
Colin Bignell
I think, if it's the case that I recall, the system was the Navman GPS with 3g connectivity that is fitted to police cars and HA vehicles that continuously logs the position and speed of the car at the control room. I know of it being used the other way when an HA driver from up your end of the world was shown the exit door after he was tracked doing 100mph+ on the way to an incident. Unlike the police, the HA have no power to exceed the speed limit.
The police like to give the impression that speed cameras, VASCAR, etc are unimpeachable but I've acted as an expert witness in the past for cases where they have reported the wrong speed. One common failing on GATSOs seems to be reporting the speed for a vehicle that is just out of sight of the camera - it may have speeded up after clearing the "tick marks" but still be in range of the radar - which causes a vehicle behind to receive a ticket. One case was fairly blatant with the speed over the tickmarks being a reasonable 25mph, but reported as 40mph (from memory - about that anyway). The camera operators are too bloody lazy to check every pair of photos and calculate the speed from the tick marks, they just send out the documents assuming that the reported speed was correct.
One case that I was a witness for, the two coppers who had reported the driver for exceeding 80mph in a 40mph limit refused to attend court when it was shown that the marks that they used with VASCAR that they claimed were one mile apart were only 1//2 mile apart.
I was surprised that the magistrates treated the absence of the coppers as a matter of course and that they did not demand that the pair be brought into court. The excuses given were that one was off duty and the other was "busy with paperwork". Neither of them acceptable reasons for anyone else to avoid a court appearance.
Ah yes and not the Navman, but something similar.
Those laser guns are notoriously unreliable. If the operator has the shakes and the dot moves on the car (almost guaranteed to do that, even when tripod mounted) the gun gives a falsely high reading.
A few years ago the BBC showed a news report of drivers being tracked by laser speed cameras operated from within a van. The spot sould be seen dancing all over the car. A couple of friends complained to the police force concerned (Cleveland I think) that the guns were not being used properly and surprise, surprise nothing was done except that the video disappeared from the BBC website.
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