In this section, “highway work zone” means a construction or maintenance area on or alongside a highway that is marked by appropriate warning signs or other traffic control devices designating that work is in progress. The State Highway Administration may reduce established speed limits in a highway work zone upon a determination that the change is necessary to ensure the public safety. A county may: Designate an area on a county highway or a highway on which the county is authorized to do work pursuant to a maintenance agreement as a highway work zone; and Reduce established speed limits in the highway work zone after a determination that the change is necessary to ensure the public safety. A municipal corporation may: Designate an area on a municipal highway or a highway on which the municipal corporation is authorized to do work pursuant to a maintenance agreement as a highway work zone; and Reduce established speed limits in the highway work zone after a determination that the change is necessary to ensure the public safety. A speed limit established under this section shall become effective when posted. A person convicted of a violation of this section is subject to a fine not exceeding $1,000.