On the subject of accuracy, I had the opportunity to check my speedo on the way to Melbourne last year - 110kph on the dial was 110kph on the display over the freeway - I could not believe it!!
Not sure whether the accuracy varies at higher speeds though - have not had an opportunity to find out! They, nastily, only allow the display boards to read to 117kph - seems that in other countries *cough USA!!* it was a trend to take photos of the fastest speed you could get up on the display!!
