Here's how "fair" speed cameras are

[Doggy Styles]

Great driver, me.

I'm in the top 20% of UK drivers.

Just like 80% of UK drivers.

[EternalOptimist]

You've never seen a troupe of baboons that have gorged on fermenting fruit? The Big Market in Newcastle doesn't then appear so distant to the plains of the serengheti.

spare me a banana?

[Peoplesoft bloke]

We could do with 30 mph speed limiters on cars for town, since no matter how careful your are, you're bound to exceed the limit by a few mph occasionally, unless you drive at say 25 mph and risk being a nuisance. I recently passed a detector van and looked at my speedo and it was, fortunately, on precisely 30 mph. I hope my speedo is accurate, but I say lucky because it was on a downward stretch of open road and one could easily let it creep up to 33 mph or so before realising it, especially when you have tail-gaiters.

Some cars already have limiters. All speedos are optimistic. You won't get nicked for 33

[chicane]

Some cars already have limiters. All speedos are optimistic. You won't get nicked for 33

Go to pepipoo and tell people that.
Some scamera partnerships are nothing but spiteful.

[TimberWolf]

Some cars already have limiters. All speedos are optimistic. You won't get nicked for 33

I knew someone that was nicked for doing 34 mph. Any references for 'all speedos are optimistic'?

[EternalOptimist]

I knew someone that was nicked for doing 34 mph. Any references for 'all speedos are optimistic'?

yes, that was the camera saying 34.
the speedo probably said 38

[Peoplesoft bloke]

I knew someone that was nicked for doing 34 mph. Any references for 'all speedos are optimistic'?

Only a lifetime reading What Car,Autocar,Car etc road tests (never read one where indicated wasn't > actual) and personal comparison of gps speeds and speedos.

[expat]

I knew someone that was nicked for doing 34 mph. Any references for 'all speedos are optimistic'?

No, but another way of looking at the logic of that:
1. speedo must read to 10% accuracy at 30 mph.
2. regardless of #1, you are not allowed to exceed the speed limit.

Result: manufacturers aim for a bit of "optimism", so that their permitted error is bound to be on the safe side.

[TimberWolf]

Only a lifetime reading What Car,Autocar,Car etc road tests (never read one where indicated wasn't > actual) and personal comparison of gps speeds and speedos.

Looks like you're right, speedometer regulations specify that they must err on the safe (overestimating speed) side:

As with the UNECE regulation and the EC Directives, the speedometer must never show an indicated speed less than the actual speed.
http://en.wikipedia.org/wiki/Speedometer

[Peoplesoft bloke]

No, but another way of looking at the logic of that:
1. speedo must read to 10% accuracy at 30 mph.
2. regardless of #1, you are not allowed to exceed the speed limit.

Result: manufacturers aim for a bit of "optimism", so that their permitted error is bound to be on the safe side.

Indeed and since 3mph is 10% you won't get nicked for 33