straight drivers only need apply

inane observation on the road to vegas: exactly how does one obtain the "oversize load" driver gig? to the uninformed, there are individuals who operate a standard-sized car that trails extra-wide trucks with a sign appended that indicates "OVERSIZE LOAD", a very helpful reminder to those of us who are otherwise inclined to tailgate 20-ton 18-wheelers as a matter of course.

is it a fulltime position--does every shipping company have a specific "oversize load" driver? are they truck-driving school dropouts? do they lack the self-awareness gene that occasions the onset of pride, vanity, and shame in the rest of us, when they regale others about their chosen profession, or when they're alone with their thoughts cruising down I-5 at 55.3MPH?