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Anyone know how accurate the signs that the police use that display your current speed are? The ones that refresh and display the current speed every second or so? Just, I drove past one of them earlier at what I thought was 28-29mph, and it flashed up 22. Just wondering if the sign was way out of it my speedometer is overreading hugely.

Theres one out our way (Cumbernauld)

Which always reads 36Mph.

when i went to yarmouth there was a sign that either displayed a happy or sad face indicating over the speed limit or within the limit!

Not as good though as you cant tell how fast ur goin if it smiles

Grrr. Local to me there's a road with a 60mph limit. It has a fair few minor roads joining, but most are well graded with good visibility (we're talking 3/4 of a mile in a straight line here, with hatched turning lanes).

About six months ago, the local council decided to put speed warning signs up about half a mile from each junction. No problems, but:
a) these signs just flash up "slow down"
b) they seem to trigger somewhere around 45mph (recall, this is a NSL zone).

Result - all the numpties twadle along at 40 - see my comments about the (good) condition of the road above. All this has done is increased the overtaking going on on the road and that must, surely, make it less safe.

Oh yes, and to cap it all, I can't recall a single accident on that road in all the time I've lived here.

dino wrote:when i went to yarmouth there was a sign that either displayed a happy or sad face indicating over the speed limit or within the limit!

Not as good though as you cant tell how fast ur goin if it smiles

The one the police use around here has the best of both worlds - flashes up your speed, then flashes up a happy or unhappy face as it's recalculating your speed

dont know on the accuracy of the sign, but i doubt it's under-reading by much - maybe 1mph to keep the anti-camera lobby from baying for their blood by seeing it register "30mph" when they cruise by with the GPS showing 29.6...

far more likely that your speedo is well out of whack? borrow a GPSalyser and see what the truth is.

if it's well out then you can start some kind of sh*t-stirring campaign that you were going to use the sign to recalibrate your speedo, and if you hadnt thought to investigate it you could have gone past a camera at 36 thinking you were safe at 30...

can't say i've seen many of these clever devices around myself; just the three, and one wasn't working.

first is the pretty well planned-for and installed pair around a dodgy corner on the A446 (can take it at 60 in the wet, but it's a blind 90 degree job with a junction on the outside and a sharp gradient change from about 1-in-10 to flat)... it still has the old signs which have a regular large warning triangle with a bend + junction symbol and a "MAX 35 MPH" plate underneath, but now about 100 yards back from them there are signs which light up with a similar triangle and SLOW written underneath. testing them i found you have to pass at a little over 45mph to trigger it, so not bad. Though, I would argue that given the run-up, any driver or any vehicle actually approaching at 40mph or less should be given an even more severe warning (a truck of such dimensions probably doesnt corner very well; and an old dodderer may just plough straight on down the wrong side of the split junction) and probably have a photo snapped so a traffic-obstruction fine can be slapped on anyone driving something capable of 50 or more on the open road.

second is one policing a 40mph limit around an at-first dicky crossroads on another road near to that one; it has a pub on one corner and is in a dip. However, driving it a couple times, the sight lines are easily good enough for 60 and it has pedestrian refuges etc. still, the signs light up for anyone doing 30 or more. (this time a 40mph sign - not a crossroads hazard sign - and SLOW DOWN). still, there are no cameras on this road, and it seems to be effective in keeping people from blasting through the junction completely thoughtlessly.

third is a rather tacky looking speed measurement thing halfway up a very tall lamp post by what is a truly diabolical right turn at the end of a dual carriageway (going down to a 4 lane single carriageway into a heavily urbanised areas, with a popular commuter route going rightwards against 2 lanes of traffic), congested so much that i often go up a little way and turn round due to the length of the queue. it looks like it was bought at tescos and has three digits - a bit excessive, not least because it's at the end of a 40 going to a 30, or because of the traffic, but because anyone managing over 80 on the bend it sits next to must be mad or in an F1 car. The rejoining of the two strips of tarmac is quite sudden and severe! (the other side stays straight, and the centre verge is enormous - they could solve half the congestion troubles by cutting an extra turn-right lane into it).
i've never seen it working. ever.

no smiley faces unfortunately

oh and there's a couple obnoxious ones opposite seemingly perma-roadworks on the m42 and on the a52 round notts, but i along with everyone else completely ignore them. interestingly they appear to be settable between 20 and 60mph but use unique patterns of bulbs for each rather than seven-segs.

we have one that just says 30MPH! if u got over that it flashes! except i've gone through it at 35mph and it hasn't gone off!

the ones that tell u wot speed u are doing are a bit stupid, as a friend of mine found out! u just try and get the highest speed possible to show up!

they put one up one the motorway downthe road from here during some road works

we spent hours trying to make it read over 100 cos it only had 2 digits on its display

but it was all coned and then there was a sharp chicane just after and it was scary lol

I heard that all *moden* cars are programmed to read 5mph SLOWER than what you are actually doing, to allow for things like police cameras...

doug&dan wrote:we have one that just says 30MPH! if u got over that it flashes! except i've gone through it at 35mph and it hasn't gone off!

the ones that tell u wot speed u are doing are a bit stupid, as a friend of mine found out! u just try and get the highest speed possible to show up!

Yeah, great fun.. if they're unmanned Unfortunately this was a temporary one, overlooked by the mobile police station and with a patrol car positioned just down the road to bring you in for a little chat if you tried anything stupid. Obviously they can't actually give you a ticket based on the sign, but I don't fancy having a chat with a copper in the mobile unit very much

I heard that all *moden* cars are programmed to read 5mph SLOWER than what you are actually doing, to allow for things like police cameras...

Yeah, usually there's a 5-10% overread on the speedometer in order that you can't blame the car manufacturer if you get done for doing 0.5mph over the camera trigger speed when you thought you were dead on it.. thing is, if I thought I was doing 29 and I was doing 22, then that's a 24% overread, which is a bit excessive!