Sec. 3. The maximum speed limits set forth in section 2 of this chapter may be altered as follows:
(1) By local jurisdictions under section 6 of this chapter.
(2) By the Indiana department of transportation under section 12 of this chapter.
(3) For the purposes of speed limits on a highway on the national system of interstate and defense highways, by order of the commissioner of the Indiana department of transportation to conform to any federal regulation concerning state speed limit laws.
(4) In worksites, by all jurisdictions under section 11 of this chapter.