In those counties where the road supervisor’s plan is adopted, county road and bridge funds shall only be paid out upon itemized bills or estimates showing in detail the time, place and character of work done, or in detail the supplies or materials purchased and received for county road and bridge purposes, duly rendered and approved by the road supervisor of the road district in which such work is done or for which such supplies of materials are purchased and received, by warrant drawn by the board of county commissioners on the county road and bridge fund.