Have general charge of the roads of his district, keep the same in repair and to improve them so far as practicable and cooperate and assist in the construction or improvement of such roads with labor furnished, in whole or in part, by the Department of Human Services (acting as successor to the State Department of Public Aid under the Department of Human Services Act) or other public assistance authorities; except that a highway commissioner may not permanently post at a reduced weight limit any road or portion thereof unless the decision to do so is made in accordance with Section 6-201.22 of this Code.