Texas Transportation Code - TRANSP § 601.078. Additional Coverage

(a) An insurance policy that provides the coverage required for a motor vehicle liability insurance policy may also provide lawful coverage in excess of or in addition to the required coverage.

(b) The excess or additional coverage is not subject to this chapter.

(c) In the case of a policy that provides excess or additional coverage, the term “motor vehicle liability insurance policy” applies only to that part of the coverage that is required under this subchapter.