ask Woody, all police cars speedos are recalibrated to the exact speed. Think most are out by about 5 mph
Thats not quite true, but nearly. Most are accurate at lower speeds, eg less than 40mph. And then they get progressively worse, my 200 says its doing 80mph, but satnav says 74mph.
Because the speedos are now electronically controlled, the manufacturers build this in as a 'licence saver,' you think your going faster than you are! I'm sure they could be calibrated correctly as well.
There was an article in Evo mag about this last year IIRC, Audi was the most accurate doing 140mph, indicated 142mph.