As provided by Section 52, Article III, Texas Constitution, to construct, maintain, and operate macadamized, graveled, or paved roads or turnpikes, or in aid of those activities, two or more adjoining counties or portions of adjoining counties through a road district established under this subchapter may:
(1) issue bonds in any amount not to exceed one-fourth of the taxable value of the real property located in the district;
(2) impose an annual ad valorem tax to pay the interest on the bonds; and
(3) provide a sinking fund for the redemption of the bonds.