Nice. I have had to literally quote their own code to them before they get the picture.
I once had 4 cops pouring over the criminal code and drivers statutes for over an our before they finally let me go. I then sent the department a bill for $150 for my time which they paid because they didn't want me to sue them for it.
A motor vehicle is legally defined as used for commerce. Your automobile is your means of transportation. They are two different and distinct things that have nothing to do with each other.