Tex. Transportation Code § 460.551

(a) The board of directors may impose for an authority a sales and use tax at the rate of:

(1) one-quarter of one percent;

(2) three-eighths of one percent;

(3) one-half of one percent;

(4) five-eighths of one percent;

(5) three-quarters of one percent;

(6) seven-eighths of one percent; or

(7) one percent.

(b) The imposition of an authority's sales and use tax must be approved at an election conducted in the manner provided by this chapter and may not be imposed in an area that has not confirmed the authority.

(c) A sales and use tax may be imposed, as prescribed by this section, by a municipality that participates in a transportation or transit authority other than an authority created under this chapter if:

(1) the combined rates of all sales and use taxes imposed in the municipality does not exceed two percent; and

(2) the ballot of the authorization vote for the sales and use tax reads:

"(Name of city) already imposes a sales and use tax for participation in the (name of transportation or transit authority). The proposed sales and use tax is solely for the benefit of, and will be dedicated to, the (name of authority created under this chapter)."

(d) The authority shall impose a sales and use tax at a minimum uniform rate as determined by the board of directors if the tax is approved at an election in an area that has confirmed the authority.

(e) A municipality with a population of 12,000 or more that has confirmed the authority may impose a sales and use tax at a rate higher than the minimum uniform rate established under Subsection (d) on approval at an election if the authority will provide the municipality a higher level of service.