Garda speed guns

Euphoriasean

Lads,

Just passed a guard standing in a roundabout with a speed gun. The squad car was parked off the roundabout but didn't appear to be anyone else in it. She would never had time to cross the roundabout and get in the car in time. Though they had to pull you over to issue you. Was doing 55 in a 50 zone. Could I expect to receive a notice.

Thanks

Cee-Jay-Cee

No. If they're using the speed gun then they have to stop you to inform you that you are going to receive a ticket.

On a side note, most car speedometers read over by between 5-10% so you were doing the limit or barely above it.

_Kaiser_

Recent "oh oh" moment on a quiet motorway when I pulled out to overtake a truck and just as I passed it, I passed one of their ramps which had the car pretty well concealed and the guy pointing the speed gun over the bonnet.

Watched him in the mirror as he turned and pointed it after me, but he didn't come chasing so I got away with it.

ED E

Just because you didnt see his mate doesnt mean he wasnt hiding 200m further on.

lway

_Kaiser_ wrote: »

Recent "oh oh" moment on a quiet motorway when I pulled out to overtake a truck and just as I passed it, I passed one of their ramps which had the car pretty well concealed and the guy pointing the speed gun over the bonnet.

Watched him in the mirror as he turned and pointed it after me, but he didn't come chasing so I got away with it.

Speaking of well concealed, I once passed a Motorcycle Guard sat on the ground on the hard shoulder of the M8 with his knees up hiding his Hi-viz top with a speed gun. The bike was hidden in the gateway beside him. Really didn't see him until I was passing him.

CeilingFly

Cee-Jay-Cee wrote: »

On a side note, most car speedometers read over by between 5-10% so you were doing the limit or barely above it.

Maybe 20 years ago that applied, but these days speedometers are very accurate.

Esel

CeilingFly wrote: »

Maybe 20 years ago that applied, but these days speedometers are very accurate.

Do they adjust themselves according to tyre wear?

_Kaiser_

lway wrote: »

Speaking of well concealed, I once passed a Motorcycle Guard sat on the ground on the hard shoulder of the M8 with his knees up hiding his Hi-viz top with a speed gun. The bike was hidden in the gateway beside him. Really didn't see him until I was passing him.

I recently encountered 2 Tipp boys tearing down the outside lane of the M8, only to find them setting up at the top of a hill in a gateway just beside a bridge, not 300m from one of their actual ramps.

Here: https://goo.gl/maps/U6LqpbZ2syz

About halfway between Exit 9 and 10 southbound.

CeilingFly

Esel wrote: »

Do they adjust themselves according to tyre wear?

Tyres between brand new and end of life will change speedo by less than 2km/hour

Think if the manufacturers added 10% - that would mean extra 10% mileage showing too, and resulting in warranties ending sooner than they should because of false readings - there was a court case on this year's ago.

Julie1967

Cee-Jay-Cee wrote: »

No. If they're using the speed gun then they have to stop you to inform you that you are going to receive a ticket.

On a side note, most car speedometers read over by between 5-10% so you were doing the limit or barely above it.

Just wondering if this is still the case, that they have to stop you to issue you a fine. I was on the motorways yesterday doing 131 in a 120 zone and seen hairs really well hidden stood out of the car with a speed gun.

colm_mcm

Chances are you’d have been under an actual 120kmph if your speedo was reading 131.

ei9go

CeilingFly wrote: »

Maybe 20 years ago that applied, but these days speedometers are very accurate.

Not actually correct.
Most Nissan and Toyota are 7 - 10% out

begbysback

Euphoriasean wrote: »

Lads,

Just passed a guard standing in a roundabout with a speed gun. The squad car was parked off the roundabout but didn't appear to be anyone else in it. She would never had time to cross the roundabout and get in the car in time. Though they had to pull you over to issue you. Was doing 55 in a 50 zone. Could I expect to receive a notice.

Thanks

If they dont have time to chase then they can opt to shoot you dead on the spot

Del2005

CeilingFly wrote: »

Maybe 20 years ago that applied, but these days speedometers are very accurate.

The car will know exactly what speed it's doing but the speedo will always show faster than you are going. On some cars you can access the diagnostics and see the correct speed vs the speedo speed.

JamesM

[QUOTE=Originally Posted by CeilingFly View Post
Maybe 20 years ago that applied, but these days speedometers are very accurate.

colm_mcm;106176252]Chances are you’d have been under an actual 120kmph if your speedo was reading 131.[/QUOTE]


Golf SV Speedometer = 130. Satnav = 123.

i57dwun4yb1pt8

CeilingFly wrote: »

Maybe 20 years ago that applied, but these days speedometers are very accurate.

wrong

Henry Ford III

CeilingFly wrote: »

Maybe 20 years ago that applied, but these days speedometers are very accurate.

I don't think they are. I'm lucky enough to get a new car every year and check speedo vs gps every year.

The 181 car's speedo is c.5% optimistic, which is similar to most of the others.

liamog

Our Hyundai is 4km/h out, matched against GPS and those check your speed signs.

Indricotherium

Henry Ford III wrote: »

I don't think they are. I'm lucky enough to get a new car every year and check speedo vs gps every year.

The 181 car's speedo is c.5% optimistic, which is similar to most of the others.

Why are you sure it's the GPS that is accurate?

Riva10

Indricotherium wrote: »

Why are you sure it's the GPS that is accurate?

Oh for Chr!$t sake. Leave it go. :mad: Just about fed up of this $h!te

Del2005

Indricotherium wrote: »

Why are you sure it's the GPS that is accurate?

The GPS and speedo are both as accurate as each other, GPS looses accuracy on hills the speedo due to tyre wear and pressure.

Law requires that your European spec car will always over state your speed, so that if you are ever stopped for speeding your car will always be showing faster than you are actually travelling so you have no defence to not knowing you were exceeding the limit.

Gravelly

On the speedo issue - this article explains it well.

The UK law is based on the EU standard, with some minor changes. A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph. So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph. Or to put it another way, if your speedo is reading 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph.

Incidentally, I've measured my cars speed with a high-end Garmin GPS watch, that has an altimeter, making it more accurate on hills that most sat navs, and it consistently shows my (fairly new Audi) car speedo off by between 5% and 8% depending on speed.

Clareman

I find the easiest way to find out if I'm going too fast is to have the wife in the car with me, the pressure she isapplying to their imaginary brake or the amount of white I can see in her knuckles as she's holding onto the "oh jesus handle" gives me all the readings I need.

Tabnabs

Gravelly wrote: »

Incidentally, I've measured my cars speed with a high-end Garmin GPS watch, that has an altimeter, making it more accurate on hills that most sat navs, and it consistently shows my (fairly new Audi) car speedo off by between 5% and 8% depending on speed.

Unless you have Dual-frequency GPS (you don't BTW), your little garmin watch is really not any more accurate on hills (or any where else) than any other bog standard consumer GPS units.

Gravelly

Tabnabs wrote: »

Unless you have Dual-frequency GPS (you don't BTW), your little garmin watch is really not any more accurate on hills (or any where else) than any other bog standard consumer GPS units.

I'm no expert in GPS accuracy, I just go by DC Rainmaker (who is) and his in-depth technical evaluations.

You've a lovely manner btw.

tossy

Gravelly wrote: »

I'm no expert in GPS accuracy, I just go by DC Rainmaker (who is) and his in-depth technical evaluations.

You've a lovely manner btw.

Awful manner.

Indricotherium

Gravelly wrote: »

.[/I]

Incidentally, I've measured my cars speed with a high-end Garmin GPS watch, that has an altimeter, making it more accurate on hills that most sat navs, and it consistently shows my (fairly new Audi) car speedo off by between 5% and 8% depending on speed.

Does the difference increase or decrease with speed?

Gravelly

Indricotherium wrote: »

Does the difference increase or decrease with speed?

In my case, the % difference decreases with speed.

Cordell

Tabnabs wrote: »

Unless you have Dual-frequency GPS (you don't BTW), your little garmin watch is really not any more accurate on hills (or any where else) than any other bog standard consumer GPS units.

For speed measurement purposes it has to be precise, not accurate

Indricotherium

Gravelly wrote: »

In my case, the % difference decreases with speed.

That's so strange. I'd have expected it to be the other way round.

Henry Ford III

Indricotherium wrote: »

Why are you sure it's the GPS that is accurate?

Good question. I found this which supports my evidence....

https://www.driving.co.uk/car-clinic/car-clinic-which-should-i-trust-my-speedometer-or-my-sat-nav/

Cordell

If my maths serve me well, a 10% slope (which is a large one for roads) yields a below 1% difference in distance if measured "flat", so I don't see the issue with GPS and speed accuracy when going up/down hill. Not to mention that the GPS position also includes the elevation, but I suppose the algorithm that computes the speed has to take it as a parameter.

Gravelly

Indricotherium wrote: »

That's so strange. I'd have expected it to be the other way round.

I would have too, I'm assuming it's some software in the unit between the speedo drive and the speedo, in order to keep it within the EU directive? (Could be completely wrong about this though!).

kirving

GPS is extremely accurate, and effects of altitude are 1) Negligible and 2) Accounted for in software. The GPS often has a barometer built in for altitude correction (most phones do), the mapping software can include current elevation, and the signal can be used to determine altitude as well as co-ordinates.

Cars can also work out the current height above the ground and hence tyre size/wear to millimeter accuracy using ultrasonics, calibrated camera systems, and by monitoring individual wheel speed vs. steering angle.

A 1:3, or 30% gradient, works out to be 16.7°. The actual distance traveled will only be 1.044, so 4.4% on a particularly steep hill.

For what its worth, my dashcam and phone both consistently read 117kph while the car reads 120kph.

Del2005

Gravelly wrote: »

I would have too, I'm assuming it's some software in the unit between the speedo drive and the speedo, in order to keep it within the EU directive? (Could be completely wrong about this though!).

Is the over speed reading the same? ie When showing 55 you are actually doing 50 and when showing 125 you are actually doing 120. The speedo is showing the max 10% at 50 but by just adding 5km/h to the actual speed at all times, don't forget that modern cars can show the correct speed if you can access the diagnostics.

Gravelly

Del2005 wrote: »

Is the over speed reading the same? ie When showing 55 you are actually doing 50 and when showing 125 you are actually doing 120. The speedo is showing the max 10% at 50 but by just adding 5km/h to the actual speed at all times, don't forget that modern cars can show the correct speed if you can access the diagnostics.

Think that's about right, yes.

pah

Taking the tyre wear question up a notch. I imagine then that if your car comes with 16" alloys as standard that upgrading to a set of 18"s would cause your speedo to show you travelling slower on those than on 16"s?