The Mississippi State Highway Commission is authorized, in its discretion, to have the state highway department repair any paved city streets used as a detour subsequent to the year 1944 for any United States numbered highway while the same was under construction or reconstruction, provided such paved city streets were marked by the highway commission as such detour. The extent of the repairs authorized hereby shall be to place such streets in as good condition as the same were at the time their use as such detour began, and is supplemental to the authority provided by Section 65-1-71.