[With regard to any county which is required to operate on a countywide system of road administration as described in Section 19-2-3, this section shall read as follows:]
The board of supervisors may raise funds for working, constructing, reconstructing and maintaining public roads or for building bridges by an ad valorem tax on all assessed taxable property in the county, or by a bond issue, or by either or both of said methods.
Miss. Code § 65-15-1