Umm, no, car speedos are deliberately set to display up to 10%higher than actual, so overread. This allows for tyre wear etc.
Although, as pointed out by Top Gear a good number of years ago an (as in one tested) Mondeo actually read 30 mph when the car was travelling at 31 mph. Can't remember now, but I think that was on a calibrated rolling road.
Car speedometer are allowed up to 10% over, but not under.
