Was on a speed awareness course the other day .
I was going along the A316:and dropping from 50 to 40 by Hampton , but hadn’t gone down quickly enough down the hill and got done at 48 .
Another guy had been done at 23 in a 20.
Last night coming from Kingston to Hampton Court my speedometer was 27/28 but two speed cameras signs had frowns showing 31 , so either they’re wrong or my speedometer is . Where can I go to get it checked ??
|
I'm not sure how well calibrated those roadside reminders are. There are two on my way to work and both regularly warn me for 30 even when I'm stable at that speed and using the car's limiter.
They might also be tracking other vehicles.
Is there any reason why your speedo might be out - non standard wheels or tyres for example?
The easiest way to check it is using GPS on your phone - the Google Maps app can show speed. Try to check it over a good quarter mile on a straight road. Mine shows the speedo to be accurate at 30 but under reading by 2-3mph at 70.
The other way is on a motorway using the kilometre posts and a stopwatch while holding a steady speed. You'll need an accurate km/mile conversion factor and preferably an assistant to operate the stopwatch.
|
Google maps only gives speed on non Apple phones.
There are a few GPS speed apps, I use one called Speedometer. Find a suitable road/roads, cruise control set at 30/50/70 per Speedo and see what the Phone gives you as a GPS speed.
|
>> Google maps only gives speed on non Apple phones.
Latest version of Google maps is giving inconsistent speedo. (with lots of other bugs)
|
>> I was going along the A316:and dropping from 50 to 40 by Hampton ,
>>
I don't think so.
|
|
Any inquiry to local Traffic plod might reveal where their 'Measured Mile' is and how the start and finish are marked. Could be something as innocuous as some reflective tape around a lampost. you You can then do a couple of runs say at 60 and 30 MPH.
|
>>
>> I don't think so.
>>
....all together now..... "Oh yes he was!"......
('tis the season...)
|
|
What query. I entered the A316 at Sunbury ,which is 50 to the flyover , where McD’s are in the right and Homebase , go down the other wise and it goes to 40 and there’s a camera on LHS ,
|
>> What query. I entered the A316 at Sunbury ,which is 50 to the flyover ,
>> where McD’s are in the right and Homebase , go down the other wise and
>> it goes to 40 and there’s a camera on LHS ,
yeah but, That's not Hampton.
(thought i'd get it in b4 Dunc)
|
Done for 23 in a 20. Seriously???
I wonder if he failed the subsequent attitude test.
|
>> Done for 23 in a 20. Seriously???
>> I wonder if he failed the subsequent attitude test.
I wondered about that. Police were initially reluctant to enforce in a 20.
I was on a SAC a couple of weeks ago. All caught by cameras in limits 30 or over.
|
|
I regularly use my cruise control in 30 limits now for this reason.
|
We've got one of those smiley / growly face speed devices near a roundabout on my commute to work.
They keep relocating it to any of the 4 approaches to the roundabout.
One of the approaches is on a slight bend, and subsequently because of this it gives a totally inaccurate high speed reading. Which leads me to think these devices are only accurate if you approach them straight on.
|
>> One of the approaches is on a slight bend, and subsequently because of this it
>> gives a totally inaccurate high speed reading. Which leads me to think these devices are
>> only accurate if you approach them straight on.
That's consistent with my experience.
|
There's one on my way home. I sit with cruise set at 31mph and Waze showing a steady 30, and as I approach and pass the sign I get the following:
red 32
Angry face
green 30
smiley face
green 28
smiley face
green 27 as I pass it
Every time.
I suspect it's designed to do this to encourage all motorists to slow down regardless of their actual speed.
|
Well I didn’t know him and being online , I have to accept what he said ,that he’d been done for 23 in a 20 . The 20 zones are difficult to always detect, perhaps they need to colour the roads where there is a 20 say Red tarmac , or is it just to raise funds on the pre text of safety , London. It’s 20 most places.
If you come off the A3 at New Malden and head towards Wimbledon , there’s a 2 lane section for 2 miles that seriously 3 years ago was a 40 and is now a 20 and it’s torturous to drive along in 2nd /3rd gear at 20 or less with lorries and white vans going up your
|
>>Where can I go to get it checked ??
1) a known distance (motorway mile markers?), a stop watch, and probably a passenger.
2) a straight, flat road, clear sky, a GPS speedo and a passenger
Don't forget that either of the above two methods give an average speed. Your speedo and police speed detection methods measure instantaneous speed. Well, other than average speed cameras and VASCAR (does that still exist?)
|
|
I quite like the static smiley-face speed cameras. Especially when I get a frown from speeding on my bicycle!
|
the cars speedo normally only read fast .never under. check it with a sat nav reading.
|
I haven't researched it further, but someone mentioned to me once that whilst GPS speed is accurate only on a flat road. An incline will impact the accuracy (something to do with right angled triangles).
My car has 3 spedos. The analogue one on the dash and the LCD / digital display reads the same whilst the GPS one on the larger LCD reads slower, significantly (5 to 7 mph) at times.
I was running errands today and noticed quite a number of speed traps in the area (police with speed guns). Nice, catching folk just before Xmas.
Last edited by: zippy on Sat 18 Dec 21 at 02:51
|
|
I don't think the incline thing is true. There was a chap who thought similar, i don't remember the exact details but it was a speed camera on a slight curve, he happened to be a physics/maths professor. He took it loads of appeals at court with lengthy scientific evidence as to why it was inaccurate. He lost.
|
>> I haven't researched it further, but someone mentioned to me once that whilst GPS speed
>> is accurate only on a flat road. An incline will impact the accuracy (something to
>> do with right angled triangles).
In a car, on the kind of roads that cars can climb, with a 9 sat fix, its not a factor
Last edited by: Zero on Sat 18 Dec 21 at 08:37
|
"I was running errands today and noticed quite a number of speed traps in the area (police with speed guns). Nice, catching folk just before Xmas."
I suspect they are out and about a lot of the time but you just don't happen upon them. I thin round here there is one or two full time kitted-out and dedicated vans and officers, albeit covering a huge area.
Though I also know that traffic used to be often tasked to watch out for some particular offence from time to time - a sort of mini blitz.
|
It's effectively the last "working" Friday before Xmas. Quiet department lunches in the pub (for business meetings, definitely not parties).
It's the same every year and Hampshire plod start advertising in October that they'll be having their usual festive blitz on drink/drug drivers.
|
|
Yup the speed guns are just an excuse to nab drivers over the drink drive limit tho I suspect they will be far fewer this year. HM's Gen public seem to have unilaterally cancelled xmas.
|
>> I was running errands today and noticed quite a number of speed traps in the
>> area (police with speed guns). Nice, catching folk just before Xmas.
And there is absolutely nothing at all that you can think of that would obviate this risk?
Give me a little while and I will see if I can think of a solution.
|
You have a GPS speed on your car display?
Or is it linked to your satnav?
|
>> someone mentioned to me once that whilst GPS speed is accurate only on a flat road. An incline will
>> impact the accuracy (something to do with right angled triangles).
I drove a van fitted with the Lightfoot driver monitoring system a while back. On one particular downhill entry slip road to the A1(M) it would consistently go haywire, because it believed the van was accelerating much harder than it actually was.
Its other foible happened when leaving the loading bay behind the shopping centre in Welwyn Garden city and immediately entering the underpass at 10mph, if I emerged at the other end doing 25mph the system read it as an almost instantaneous gain of 15mph at an improbable rate of acceleration - giving yet more negative marks to the driver.
|
Speed calibration - Bromptonaut
