The following combinations will be regarded as one motor vehicle for purposes of this part,
(a) a tractor and trailer or semitrailer when the tractor is engaged solely in drawing the trailer or semitrailer, and
(b) a truck and trailer when both together bear a single load.
Reproduced verbatim from the electronic Code of Federal Regulations (eCFR), the official U.S. government source. X3 Fleet Safety LLC is a compliance-services company, not a law firm; this page is regulatory reference, not legal advice. X3 is not affiliated with FMCSA or USDOT.