He does not indicate what state he is in. But here is a common statement pulled from an on-line state towing laws information site.
Indiana Trailer Dimension Laws
Total length: 65 feet; trailer length: 40 feet; width: 102 inches; height: 13 feet 6 inches.
Florida Trailer Dimension Laws
Total length: 65 feet (excludes safety devices approved by the state); trailer length: 40 feet (excludes safety devices approved by the state); width: 102 inches (excludes mirrors and safety devices); height: 13 feet 6 inches.
From another on-line site.
Alabama
Size limitations: Height, 13'6"; Width, 8'6"; trailer length, 40'; motorhome length, 45'; combined length 65'. Triple towing is not allowed.
Best to check with local state DOTs to make verify what the laws are.