Yes, in a lot of cases, due to most air brake trailers having a GVWR of 25,000lbs or above. Trailers under 10,000 pounds GVW rarely require a CDL unless towed by a 4500 series truck or larger. Please check with your state’s transportation authority for guidance. Trailers over 10,000 pounds GVW are registered in combination with the towing vehicle. If the GCWR (Gross Combined Weight Rating = sum of truck and trailer’s individual GVWR or Gross Vehicle Weight Rating) of the truck/trailer exceeds 26,000 pounds, you need a CDL. Please check with your state’s transportation authority for guidance.   Here are some resources for more information: Pennsylvania CDL fact sheet DOT NUMBER MEDICAL CARD. UCR registration  State Police CDL flowchart