[zdragnar]

A very simple google search brought this up immediately:

https://docs.legis.wisconsin.gov/statutes/statutes/346/ix/59...

Other states have something similar on the books as well.

[DangitBobby]

Your simple search doesn't back up your position. I can assure you, going ~1MPH below the speed limit does not run afoul of that law.

[zdragnar]

I never claimed that it did.

Addendum: the margin of error on speed radar generally tends to be in the region of 2mph. You'll need to be a good deal slower than the speed limit before a police officer is likely to consider your driving to be an impairment.