All salaries and expenses of members of the patrol and all expenditures for vehicles, equipment, arms, ammunition, supplies and salaries of subordinates and clerical force and all other expenditures for the operation and maintenance of the patrol in the protection of roads and bridges maintained and constructed from the county road and bridge funds, in the regulation of traffic on highways maintained and constructed by the county shall be paid monthly by the county treasurer out of county road and bridge funds at the end of each month by warrant drawn by the county commission upon the county treasury.