Tex. Transp. Code § 545.102 : TRANSPORTATION CODE — VEHICLES AND TRAFFIC — RULES OF THE ROAD — OPERATION AND MOVEMENT OF VEHICLES — TURNING AND SIGNALS FOR STOPPING AND TURNING — Turning on Curve or Crest of Grade

An operator may not turn the vehicle to move in the opposite direction when approaching a curve or the crest of a grade if the vehicle is not visible to the operator of another vehicle approaching from either direction within 500 feet.