I guess I am the last to know

[6.7 CTD]

I also would have thought a dually with a fifth wheel on the bed would qualify as a truck tractor......albeit a light duty one.

[tom41]

In some states I have notice fifth wheels with semi trailer plates on them. would this be classified as a semi truck trailer?

[Waynem]

I am not sure, but if someone with a truck-tractor, could tell us what it says on the registration, it may help. If there is a different code, then one could possibly register there vehicle as a truck-tractor. Be prepared to pay a higher registration fee!

All my life I have referred to a truck with a 40' box trailer, or look-a-likes, as a "tractor-trailer," (Semi Tractor-Trailer) and when they are separated they are the "tractor," and the "trailer," as individual items. I have never referred to a 1 ton dually as a "tractor."

I don't think Texas DPS does either, but it could possibly be fought in court since the definition of a tractor in Wikipedia is:

"A tractor is a vehicle specifically designed to provide a high tractive effort at slow speeds, for the purposes of hauling a trailer or machinery used in agriculture or construction. Most commonly, the term is used to describe the distinctive farm vehicle: agricultural implements may be towed behind or mounted on the tractor, and the tractor may also provide a source of power if the implement is mechanised. Another common use of the term is for the power unit of a semi-trailer truck"

As 6.7 said - just might be so.