edit; That number seems hard to define. Of the 7.1 million people employed throughout the economy in jobs related to trucking activity, 3.4 million were truck drivers in 2014. There are over 10 million CDL (Commercial Driver’s License) holders in the U.S., but most are not current drivers and not all are truck drivers. There are between 2.5 million and 3 million trucks on the road today that require a driver to have some sort of CDL. Of those trucks, 1. 6 million are tractor - trailers. Of those tractor - trailers, n o more than 800,000 are used in OTR (i.e., non - local) operations.
Source [http://www.trucking.org/ATA%20Docs/News%20and%20Information/...] Page 4, footnote 6