Whenever the State Highway Commission shall determine upon the basis of an engineering and traffic investigation that any maximum speed hereinbefore set forth is greater or less than is reasonable or safe under the conditions found to exist at any intersection or other place or upon any part of the state highway system, said Commission may determine and declare a reasonable and safe maximum limit thereat which, when appropriate signs giving notice thereof are erected, shall be effective at all times, or during hours of daylight or darkness or at such other times as may be determined at such intersection or other place or part of the highway.
Laws 1961, p. 384, § 11-802.