(a) This section applies only to:
(1) a county that:
(A) borders the United Mexican States; and
(B) has a population of more than 250,000;
(2) a county that has a population of more than 1.5 million that is coterminous with a regional mobility authority; and
(3) a county that has a population of more than 190,000 and not more than 1.5 million that is coterminous with a regional mobility authority.
(b) The commissioners court of a county by order may impose an additional fee for a vehicle registered in the county. Except as provided by Subsection (b-1), the fee may not exceed $10. In a county described by Subsection (a)(3), the fee must be approved by a majority of the qualified voters of the county voting on the issue at a referendum election, which the commissioners court may order and hold for that purpose.

(b-1) The commissioners court of a county described by Subsection (a) with a population of less than 700,000 may increase the additional fee to an amount that does not exceed $20 if approved by a majority of the qualified voters of the county voting on the issue at a referendum election, which the commissioners court may order and hold for that purpose.
(c) A vehicle that may be registered under this chapter without payment of a registration fee may be registered under this section without payment of the additional fee.
(d) A fee imposed under this section may take effect and be removed in accordance with the requirements of § 502.401.
(e) The additional fee shall be collected for a vehicle when other fees imposed under this chapter are collected. The fee revenue collected shall be sent to a regional mobility authority located in the county to fund long-term transportation projects in the county that are consistent with the purposes specified by § 7-a, Article VIII, Texas Constitution.
(f) The department shall adopt rules necessary to administer registration for a vehicle being registered in a county imposing a fee under this section.