(a) The operator of a vehicle that is described by Subsection (b) and that is stopped on a roadway or shoulder shall immediately display vehicular hazard warning lamps that comply with § 547.331, unless the vehicle:
(1) is parked lawfully in an urban district;
(2) is stopped lawfully to receive or discharge a passenger;
(3) is stopped to avoid conflict with other traffic;
(4) is stopped to comply with a direction of a police officer or an official traffic-control device; or
(5) displays other warning devices as required by Sections 547.504-547.507.
(b) This section applies to a truck, bus, truck-tractor, trailer, semitrailer, or pole trailer at least 80 inches wide or at least 30 feet long.