As far as I understand your comment, driving at the speed limit is unsafe because everybody is speeding. Sounds like a self-fulfilling thing. Maybe it would be even safer if the majority would obey the speed limit?
Did you read the link I posted? Theres lots of empirical data out there that says that drivers drive the same speed on a road, regardless of the posted limit. That speed is based on their judgment of the road - sight lines, shoulder width, sharpness of curves, etc.