Whenever the board finds on the basis of an engineering and traffic survey that the
prima facie speed limit of 25 miles per hour in a business or residence district or
in a public park on any street having a roadway not exceeding 25 feet in width, other
than a state highway, is more than is reasonable or safe, and declares a prima facie
speed limit of 20 or 15 miles per hour, whichever is found most appropriate and is
reasonable and safe, as provided in Section 22358.3 of the Vehicle Code, the commissioner
shall erect and maintain appropriate signs specifying the prima facie speed limit
so determined.
