(f) Whenever local authorities within their respective jurisdictions determine upon the basis of an engineering and traffic investigation that a higher maximum speed than those set forth in subsection (b) is reasonable and safe, or that any speed hereinbefore set forth is greater than is reasonable and safe, under the conditions found to exist upon any part of a street within the corporate limits of a municipality and which street is a part of the State highway system (except those highways designated as part of the interstate highway system or other controlled-access highway) said local authorities shall determine and declare a safe and reasonable speed limit. A speed limit set pursuant to this subsection may not exceed 55 miles per hour. Limits set pursuant to this subsection shall become effective when the Department of Transportation has passed a concurring ordinance and signs are erected giving notice of the authorized speed limit.
When local authorities annex a road on the State highway system, the speed limit posted on the road at the time the road was annexed shall remain in effect until both the Department and municipality pass concurrent ordinances to change the speed limit.
The Department of Transportation is authorized to raise or lower the statutory speed limit on all highways on the State highway system within municipalities which do not have a governing body to enact municipal ordinances as provided by law. The Department of Transportation shall determine a reasonable and safe speed limit in the same manner as is provided in G.S. 20-141(d)(1) and G.S. 20-141(d)(2) for changing the speed limits outside of municipalities, without action of the municipality.