Combining U.S. and Canadian tractor-trailer operations that hold FMCSA authority, the picture is essentially the same, with 1-tractor operations making up 58.5% of carriers but only 7.9% of tractors and 4% of trailers. Carriers with more than 500 tractors represent 0.1% of carriers but 30.7% of tractors and 37.5% of trailers.