how accurate are speed monitors

jjames_3

They are a good idea because they make you jump if you're in an area you've never been to before and you creep over the speed limit a bit (far more dangerous IMO than if you go 2-3mph over on a road you've traversed a thousand times before). They're there as gentle reminders in the main, and are used a lot in County Durham where there are no fixed speed cameras (the chief constable here doesn't believe in them).

As for accuracy of speedos, I don't think it's related particularly to the model of car, more the individual calibration, and also what wheels/tyres you're using. If the car is upgraded to low-profiles etc this can throw out the accuracy of the speedo significantly.

FWIW our old Nissan Sunny seems to read 33 in a 30, so about 10% out (I put this down to age). Our much newer Hyundai seems to be nigh-on completely accurate (30 in a 30, 60 in a 60, and reads 100 when doing 98 according to a couple of pieces of satnav software). Hyundais are known for their accurate speedos, not sure why, but they tend to be well calibrated for some reason.

Wig

zappahey wrote:

Complete nonsense. According to the law, a speedo may not under read but can over read by 10%

Plase quote your law chapter & verse.

My understanding is based on a motoring TV programme I saw ages ago which explained how analogue speeos can be inaccurate. My memory is usually very good, and I will try to find some links on inaccurate speedos.

*!*HIBS*!*

Bokken wrote:

yes the speedometer is normally upto 5% out.This is factored into the calabrations on the speed cameras and allows you to exceed the stated speed by 10% ie.33mph in a 30,44mph in a 40 etc.Local forces also give you a few extra just to make sure it is worth their while prosecuting you.
So 30 limit would give you 30mph+ 10%= 33mph + another 3/5 so between 36-38mph.

FYI its best just sticking to 30mph rather than going at/about 33mph for one example.

Also if Brussels gets their way it won't be in mph but kph!

Wig

*!*HIBS*!* wrote:

Also if Brussels gets their way it won't be in mph but kph!

And about time too, normalisation is good for consumers and business.

jjames_3

*!*HIBS*!* wrote:

FYI its best just sticking to 30mph rather than going at/about 33mph for one example.

Also if Brussels gets their way it won't be in mph but kph!

This was something which we as a nation agreed to in the 1960s as part of the conditions for joining the EU.

The fact that we're still moaning about having to get round to it 40 years later says more about us than it does the EU.

Metrication is a *good* thing. Our imperial system is full of inconsistencies, and a significant proportion of our measures don't match up with the "US" system, leading to immense confusion.