Nothing has changed, nor is it unusual. Maybe the US has just caught up.

AIUI, legislation in the UK has required (for years now - maybe came
from a European regulation) that speedometers read between +1% and +11%
at 70mph.  In other words, by law speedometers must never under-read.
It's an obvious safety provision, as well as protecting manufacturers
from frivolous claims by motorists who are being prosecuted for speeding
and want to blame somebody else.

It happens that my old A3 over-read by about 5mph at 70mph, but my new
A3 over-reads by about 1-2mph at 70mph.  When I first got the car, I
double-checked the speedometer against the speed reading from a GPS.  I
want to be confident about my actual speeds.

The reason that I'm anal about speedometers is because I bought a new VW
Golf in 1998 which did have an under-reading speedometer.  Needless to
say, the dealer refused to believe me and tried hard to patronise me as
someone suffering from delusions.  When I became insistent enough for
them to check, they were forced to replace it PDQ especially after I had
pointed out to them that they had sold me a car which was illegal to use
on a road.  It was under-reading by about 10%, and it was obvious when
driving in traffic on a motorway.

If you carry out the same calibration yourself, you might also find it
very educational to watch how much other cars slow down for speed
cameras or around traffic cars, when you know they're already doing less
than the speed limit.  A reduction of 11% at 70mph means they are
actually doing less than 63mph.  It seems that many cars' speedometers
over-read by near to the maximum, if only the owners realised it.

Yes, I have had a traffic car tuck in behind me after I had sailed past
them and everyone else doing 65mph, only for them to leave me alone
after following me for a couple of miles.  I like to think that it would
have been plain to them that I did know what speed I was doing, unlike
most others on the road it seems, but who knows?

The Road Vehicles (Construction and Use) Regulations 1986, as amended,
allows the use of speedometers that meet the requirements of EC Community
Directive 75/443(97/39) or ECE Regulation 39. Both the EC Directive and
the ECE Regulation lay down accuracy requirements to be applied at the
time of vehicle approval for speedometers. These requirements are that the
error in the indicated speed must not be more than 10 per cent of the true
speed plus 4 km/h.  The requirements are also that the indicated speed
must never be less than the true speed.

Tony

There is no such thing as an "accurate" speedometer that used engine speed
and gear ratios to calculate speed. Your indicated speed varies according to
amount of tyre wear and whether the tyre is over or under inflated.
You the driver would certainly sue the manufacturer if booked for speeding
when your speedometer indicated you were travelling within the speed limit.
For that reason all car makers have sold cars with over-reading
speedometers, long before any law made them do such a thing.
A GPS system is certainly much more accurate as it is not affected by things
like tyre condition. Obviously such a system cannot replace the cars
speedometer as it cannot work anywhere the satellites cannot be seen.
It would also help if some smart-alecs would shut-up instead of writing
bullshit on things they obviously know nothing about.

Oldun