Whenever the board finds on the basis of an engineering and traffic investigation
that a speed of 30, 35, 40, 45, 50, 55, 60 or 65 miles per hour facilitates the orderly
movement of vehicular traffic and would be safe upon any highway otherwise subject
to a prima facie limit of 25 miles per hour under the Vehicle Code, the commissioner
shall post appropriate signs upon such highways specifying such speed limits.
