Section 56-5-1530 - Alteration of speed limits on state highway system by Department of Transportation; signs(a) Establishing speed zones. Whenever the Department of Transportation 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, the Department of Transportation may determine and declare a reasonable and safe maximum limit thereat, which shall be effective when appropriate signs giving notice thereof are erected. Such maximum speed limit may be declared to be effective at all times or at such times as are indicated upon such signs; and differing limits may be established for different times of day, different types of vehicles, varying weather conditions, and other factors bearing on safe speeds, which shall be effective when posted upon appropriate fixed or variable signs.(b) Setting maximum limits in state highway extensions in urban districts. The Department of Transportation shall determine the proper maximum speed for all state primary highway extensions into and through urban districts and shall declare a reasonable and safe maximum speed limit thereon which may be greater or less than the maximum speed otherwise permitted under this article for an urban district and such maximum speed limits shall be effective at all times during hours of darkness and at other times as may be determined when appropriate official signs giving notice thereof are erected upon such street or highway.1993 Act No. 181, Section 1405; 1966 (54) 2244; 1949 (46) 466; 1952 Code Sections 46-367, 46-369; 1962 Code Section 46-362.