Excellent excellent excellent!

[Dean Lofthouse]

Now it is fashionable to assume (a) that all motorists are evil and should be punished, and (b) motorists who exceed the speed limit are the most evil .

 

 

I'd go with that

 

You are correct about the 10% speedo thingy.

 

If you have sat nav it can show the variation in speedo reading quite dramatically if you transfer it from one vehicle to another.

 

My landrover is bang on with the tomtom whereas the landcruiser was 10% below what the sat nav read

[LancsMike]

Not so, I am afraid.

 

The 10% +3 threshold was one that ACPO (the Association of Chief Police Officers) decided was sensible simply to prevent police forces (sorry - they're "services" now not forces) from being overwhelmed with paperwork and prosecutions. If you book *everybody* who is even slightly over the limit the whole system will grind to a halt due to the sheer volume of speeding tickets. However it is not the law and it is not mandatory. Now it is fashionable to assume (a) that all motorists are evil and should be punished, and (b) motorists who exceed the speed limit are the most evil and should be treated like would-be murderers, many police "services" are choosing to ignore the ACPO guidelines and prosecute everyone.

 

The issue of speedometers is equally misunderstood. By law a speedo may be inaccurate by (if I recall correctly) no more than 10% but it must not under-read at all, so if for example it is reading 50mph you could actually be doing anything from 45mph to 50mph but not more than 50mph. However it is not cost effective to manufacture a speedo to these specs (i.e, making one that is guaranteed not to under-read) and most good modern speedos are approximately plus/minus 5%. They are therefore designed to over-read by 5%, since they will therefore be legal with the +/-5% accuracy on top of this - they will never under-read. In this way if you have a +/-5% speedo designed to over-read by 5%, when it shows 50mph you ought to be doing 47.5mph +/- 2.5mph which keeps everything legal.

 

Police traffic vehicles have calibrated speedos (expensive) which will probably be less than 1% variant from true.

 

The bottom line is that if you are even 1mph over the limit you could be done for speeding.

 

Thats pretty interesting Treewolf, had no idea it actually worked that way, will keep it in mind in the future thanks

[rotax81]

damn! that means more patrolling plod, them camera's never bothered me on the bike

[Treewolf]

Thats pretty interesting Treewolf, had no idea it actually worked that way, will keep it in mind in the future thanks

 

Glad to be of service!

 

Many times I have learned really useful stuff from this forum, and I am glad that for once I can give something back!