(a) Except as provided by Subsection (b), a motor vehicle, trailer, semitrailer, pole trailer, or combination of those vehicles shall be equipped with brakes that comply with this chapter.
(b) A trailer, semitrailer, or pole trailer is not required to have brakes if:
(1) its gross weight is 4,500 pounds or less; or
(2) its gross weight is heavier than 4,500 pounds but not heavier than 15,000 pounds, and it is drawn at a speed of not more than 30 miles per hour.