A. Whenever the secretary of highway and transportation determines upon the basis of an engineering survey and traffic investigation, a detailed report of which is filed with the traffic safety bureau of the state highway and transportation department, that any speed established by law is greater or less than is reasonable or safe under the conditions found to exist upon any part of a state highway, the secretary of highway and transportation may declare the speed limit for that part, and that speed limit shall be authorized and effective when appropriate signs giving notice thereof are erected at that particular part of the highway; provided that no speed limit shall be declared greater than seventy-five miles per hour. The declaration of speed limits by the secretary of highway and transportation shall not be considered rules for purposes of the State Rules Act [N.M. Stat. Ann. Chapter 14, Article 4].

B. Whenever a local authority determines upon the basis of an engineering survey and traffic investigation that any speed limit permitted under state law or local ordinance is greater or less than is reasonable or safe under the conditions found to exist upon any part of a highway within its jurisdiction, it may declare a speed limit for that part, and that speed limit shall be authorized and effective when appropriate signs giving notice thereof are erected at that particular part of the highway; provided that no speed limit shall be declared greater than seventy-five miles per hour.

C. Engineering surveys and traffic investigations made by local authorities shall be on a form approved by the secretary of highway and transportation. If engineers are not available to the local authorities, the state highway and transportation department may make the surveys and investigations for the local authorities.

D. Speed zones may be marked by a sign containing a flashing yellow light and, when the light is in operation, the speed limit, instructions or regulations on the sign are in effect.

E. Alteration of speed limits on state highways by local authorities is not effective until approved by the secretary of highway and transportation.

F. The provisions of Subsections A and B of this section shall not apply to changes of speed limit in construction zones authorized pursuant to Section 66-7-303.1 N.M. Stat. Ann..