MAXIMUM LENGTH OF SEMITRAILER OR TRAILER.
Tex. TRANSP Code § 621.204.
in effect(a) A semitrailer that is operated in a truck-tractor and semitrailer combination may not be longer than 59 feet, excluding the length of the towing device.
(b) A semitrailer or trailer that is operated in a truck-tractor, semitrailer, and trailer combination may not be longer than 28-1/2 feet, excluding the length of the towing device.
(c) The limitations prescribed by this section do not include any safety device determined by regulation of the United States Department of Transportation or by rule of the Department of Public Safety to be necessary for the safe and efficient operation of motor vehicles.
(d) The limitations prescribed by this section do not apply to a semitrailer or trailer that has the dimensions of a semitrailer or trailer, as appropriate, that was being operated lawfully in this state on December 1, 1982.