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Sathya
It is legally recognised that all Speedos can have a 10% inaccuracy between actual speed and speedo reading when travelling above 10 mph. This fact is taken into consideration when detecting speeding vehicles. The reason the Police add 2mph onto the 10% is (1) to allow for %errors specified by the equipment manufacturers of the cameras, normally below 1% at maximum range and (2) the final 1 mph is added because it then becomes a speed in excess of the stated limit.

However the above does not apply to all vehicles. Any vehicle that is compelled to use a tachograph, such as lorries, large vans etc have different set of rules for calculating the allowances for determining what speed they can be booked at.

With tachographs, the law clearly states that all tachographs MUST BE ACCURATE to within 6 KPH (not mph) at any give speed. They are calibrated instruments which have been tested on rolling roads and when sealed.

A warning for drivers of tacho vehicles. The vehicle may have been calibrated with tyres with low but still legal tread. When new tyres are fitted the actual speed of the lorry will increase because of that extra 3/4 inch of tread. The driver could now face 2 charges if zapped (1) speeding (2) using a vehicle with a defective tachograph because the tacho can now be above the 6 KPH maximum tolerance. As these drivers know the tacho is the spy in the cab so when they check your card, it's case proven M'lud.
Homer
QUOTE (Sathya)
It is legally recognised that all Speedos can have a 10% inaccuracy between actual speed and speedo reading when travelling above 10 mph. This fact is taken into consideration when detecting speeding vehicles. The reason the Police add 2mph onto the 10% is (1) to allow for %errors specified by the equipment manufacturers of the cameras, normally below 1% at maximum range and (2) the final 1 mph is added because it then becomes a speed in excess of the stated limit.


Speedometers can only over read, they must not under read.
Sathya
With respect to your posting where you quote.
QUOTE
Speedometers can only over read, they must not under read.
.

Your comment is incorrect. A tolerance is given which can be either side of actual.

From what you suggest please consider the following.

Your speedometer reads 50 mph but because of your suggested over read, you may actually only be doing 45mph . You get zapped and reported for doing 57 mph ( the speed limit + 10% + 2mph).

Using your quote of under read only again, 50 mph less 10% is 45 mph. using a now possible 45 mph actual speed + 10% + the 2mph discretion, you would get prosecuted for doing a possible 51 mph and somehow I don't think anyone has ever heard of a succesful prosecution for 51 mph in a 50 limit which if your quote is correct would be a common sight.

Allowing for your comment, this would mean that your speedometer could actually have a 22% under read. I think not!

The figures I quoted for maximum tachograph errors are those stipulated by the ministry of transport and compulsory by Law.

If from what you say is correct then surely they would impose a larger tolerance so that vehicles would be going EVEN SLOWER without having to ammend existing speed limits imposed on these vehicles.

To finish, I beg to differ from your posting.
Talion
Sathya from your figures you seem to think the scamera know what your speedo is reading.

if you got a ticket for 57mph, your speedo would be reading anything upto 64/65 mph,

if you got a tickey for 51mph your speedo would be reading upto 58/59 mph !


QUOTE (Sathya)
QUOTE
Speedometers can only over read, they must not under read.
.

From what you suggest please consider the following.

Your speedometer reads 50 mph but because of your suggested over read, you may actually only be doing 45mph . You get zapped and reported for doing 57 mph ( the speed limit + 10% + 2mph).

.
Mudster
QUOTE (Sathya)
Your speedometer reads 50 mph but because of your suggested over read, you may actually only be doing 45mph . You get zapped and reported for doing 57 mph ( the speed limit + 10% + 2mph).


Why would you get reported for 57mph? You're only actually doing 45mph with the speedo indicating 50mph.


QUOTE (Sathya)
Using your quote of under read only again, 50 mph less 10% is 45 mph. using a now possible 45 mph actual speed + 10% + the 2mph discretion, you would get prosecuted for doing a possible 51 mph and somehow I don't think anyone has ever heard of a succesful prosecution for 51 mph in a 50 limit which if your quote is correct would be a common sight.


Again you wouldn't be prosecuted for doing an actual 45mph in a 50 mph limit.
The tolerance is on the speedometer reading and not the measuring equipment. This is why a speedo can overread by 10%, but is not allowed to underread.
Stick Fly
So wot about my case that I am currently pleading not guilty too, where I have received 2 photos, one prior to the Time Out photo showing me doing 46mph, the second photo being the Time Out photo itself.

The speed limit was allegedly 40mph !!

The equip was allegedly a LTi 20/20, the shot was taken at a distance of 228m and another car was tailgating me.

Could I use the tolerance argument here ???

What do you think heroes?

Sticulatum Fly
Ker-ching
Hey Sticky Fly

What are you worried about? It's an LTi20-20 "dodgyscope"! You're never going to get this far in the case, because you're going to DEMAND the WHOLE video 7 days minimum before the trial, and you're going to wait and wait and wait by your letter slot listening to the silence. laugh.gif
Homer
QUOTE (Sathya)
With respect to your posting where you quote.
QUOTE
Speedometers can only over read, they must not under read.
.

Your comment is incorrect. A tolerance is given which can be either side of actual.


No, Speedometer tolerances are not +/-10% they are +10%/-0% which means they can over read by 10% but not under read. This means that if your speedo reads 70mph you are doing 70mph at the most and are possibly travelling up to 10% below that speed. (not sure where you get 22% from???)

The 10%+2mph allowance has absolutely nothing whatsoever to do with speedometer tolerance.

And, yes, people can be prosecuted for 1mph over the limit.

QUOTE
Your speedometer reads 50 mph but because of your suggested over read, you may actually only be doing 45mph . You get zapped and reported for doing 57 mph ( the speed limit + 10% + 2mph).


Ummm not sure what logic you used to come up with that. rolleyes.gif

If your speedo reads 50mph and because of the 10% tolerance you are actually travelling at 45mph the reading when you get zapped will be 45mph (assuming the device works as advertised and is being operated correctly) so you won't get a ticket at all.

Sorry for banging on about this but people come here for facts and I wouldn't like somebody to read Sathya's posts and think they are correct.
Sathya
The quote made earlier was made by HOMER and not myself.

All I was doing was giving examples to show him how his quotation was incorrect.

Accorging to Homer all speedos must over read and must not under read which would mean a speedo reading of 50 could be an actual road speed of 45 mph.

We all know that nobody gets done for doing 51.5 mph in a 50 limit and if the camera zapps you and gives a reading of 57 mph this would mean that they have allowed 22% + 2mph above your possible 45mph road speed (50mph speedo speed according to Homer's theory) before booking you .... I think not.
Sathya
Further to my posting, just to prove Homer wrong again, I suggest people look at the following article :

http://news.bbc.co.uk/1/hi/uk/461624.stm

case proven m'lud.

Sorry Homer.
Talion
Sathya,

I understand what you are saying, and if that was the case, I would assume it;s upto the offender to prove the speedo was not working correctly, if in this case it was a small % out i'm sure they would cancel the ticket with proof of the error and correction !

if it was a large ammount say 10-50 mph+ then they may try to do you for having a dodgy speedo(just my guess)

However on leaving the factory ALL speedo's should over read NEVER under read, if they dont I guess the onus is on the owner to correct it these days !
TonyOut
There is a hack on my climate control that lets you see the true speed of the vehicle. I have one analogue and one digital, and they are both deliberatly fast!

Nice to see the manufacturer looking after your interests. Never been interested enough to see how much by though, too busy looking for scammers!
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