Okla. Stat. tit. 47, § 47-1-165: Special mobilized machinery

Special purpose machines, either self-propelled or drawn as

trailers or semitrailers, which derive no revenue from the

transportation of persons or property, whose use of the highways is

only incidental, and whose useful revenue producing service is

performed at destinations in an area away from the traveled surface

of an established open highway, and which carry no load other than

their own weight, which cannot be divided for all practical

purposes. This definition shall include a truck or truck tractor

when used while drawing special mobilized machinery but this shall

not be construed as exempting from license and registration the

pulling unit truck or truck tractor as required by the motor vehicle

license and registration.