Tex. Transp. Code § 547.606
(a) A road tractor, truck, trailer, truck-tractor in combination with a semitrailer, or semitrailer in combination with a towing vehicle that has at least four tires or at least two super single tires on the rearmost axle of the vehicle or the rearmost vehicle in the combination shall be equipped with safety guards or flaps that:
Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.
Acts 2011, 82nd Leg., R.S., Ch. 752 (H.B. 1330), Sec. 1, eff. September 1, 2011.