When i go 55 kmh on the speedometer, they usually say 50 kmh on the radarscreens.
My car does the same thing, although in MPH instead of KPH. I've verified that my speedometer consistently reads 5mph faster than what I'm really going. This is with my GPS, with the radar installations, and I've even used those little mile-marker signs in Oregon in coordination with my cruise control.

I wonder if this is a conspiracy by the car companies and/or the government to make us slow down? I've got a call in to CarTalk with this very question. Maybe they'll put me on the show with it?
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Tony Fabris