State law prohibits parking on a highway bridge and generally forbids (with certain exceptions) parking in the main traveled part of a highway.
Within a public road’s right-of-way, private fencing that restricts public passage to the stream is illegal.
Defendants ... entered the waters of Diversion Lake and fished in it by placing their boats into the water from the low bridge on which the public road crosses the river and the lake near the upper end of the lake. Thus they were able to obtain access to the waters of the lake without trespassing upon the property of plaintiff ... .Regarding parking, see the Texas Transportation Code, §§ 545.301-545.305.
In Cornelison v. State, 40 Tex. Crim. 159, 49 S.W. 384 (1899), a private party owned land on both sides of a 30-foot wide roadway. A 14-foot wide bridge spanned a creek. The landowner ran fences to the bridge corners, obstructing 8 feet of right-of-way on each side of the bridge. The court upheld a criminal conviction of the landowner for obstructing a public road.
Today obstructing a highway or other passageway is a misdemeanor under Texas Penal Code § 42.03 (quoted on pp. 12-13 below).