In this chapter:
(1) "Air quality project" means a project or program of the department or another governmental entity that the commission determines will mitigate or prevent air pollution caused by the construction, maintenance, or use of public roads.
(2) "Bond" means bonds, notes, or other obligations issued under Subchapter C or another law with respect to a toll project or system.
(3) "Region" means:
(A) a metropolitan statistical area and any county contiguous to that metropolitan statistical area; or
(B) two adjacent districts of the department.
(3-a) "Registered owner" means an owner as defined in Section 502.001.
(4) "System" means a toll project or any combination of toll projects designated as a system under Section 228.010.
(5) "Toll project" has the meaning assigned by Section 201.001(b).
(6) "Transportation project" means:
(A) a tolled or nontolled state highway improvement project;
(B) a toll project eligible for department cost participation under Section 222.103;
(C) the acquisition, construction, maintenance, or operation of a rail facility or system under Chapter 91;
(D) the acquisition, construction, maintenance, or operation of a state-owned ferry under Subchapter A, Chapter 342;
(E) a public transportation project under Chapter 455 or 456;
(F) the establishment, construction, or repair of an aviation facility under Chapter 21; and
(G) a passenger rail project of another governmental entity.