Upon the adoption of a resolution stating that a county responsibility or purpose will be served, the county commissioners shall also in their respective counties have the power to expend from any highway funds under their control and jurisdiction such sums as they may deem necessary to pay all or a portion of the cost of highway projects within municipal corporations, including repairing or replacing bridges and the approach roads thereto when such bridges and approaches are located wholly or partially within an incorporated town or municipality within such county.