Tex. Transp. Code § 547.355
(b) A reflector required by this chapter mounted on a vehicle subject to this subchapter shall be visible from the rear, if a rear reflector, or from the applicable side, if a side reflector, at nighttime at all distances from 100 to 600 feet from the vehicle when the reflector is directly in front of:
Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.