In this subtitle:
(1) "Highway" includes a tolled or nontolled public road or part of a tolled or nontolled public road and a bridge, culvert, building, or other necessary structure related to a public road.
(2) "Improvement" includes construction, reconstruction, maintenance, and the making of a necessary plan or survey before beginning construction, reconstruction, or maintenance.
(3) "State highway system" means the highways in this state included in the plan providing for a system of state highways prepared by the director under Section 201.103.