WSIC is an acronym with multiple interpretations, one of which is relevant here. For our purposes, it means "wide-span implement carrier" and refers to a category of machine wherein the components that do useful work are suspended from a beam (gantry) which is supported by wheeled tractors (trucks) at either end.
This arrangement allows the positioning of the active components over any portion of a strip of land as wide as the machine's span and of indefinite length, while confining its wheels to narrow, widely spaced tracks, which can be graveled to mitigate damage.
Aside from the suspended components, it might be thought of as a vehicle with very wide track and relatively short wheelbase.
While such a machine might weigh as much as a conventional tractor, that weight would largely be relatively inexpensive extruded or rolled materials, welded together, as opposed to cast or forged parts with machined surfaces.