I'm glad you asked officer, the knobby tires give me more traction in case I have to cut through someones back yard. Am I free to go now? I'm running on fumes and you don't want me to get outta this tub at the gas station.
-or-
of course I don't have auto insurance, a rototiller and a bathtub are both household items and like I said I am more than willing to take you home and show you my homeowners insurance.
"Tovareesh, I um meerely on top-seekret meeshen to test a noo Amerikanski motor kleaner for spring market introduktion! Kan I interest you in sample bottle? Wash your motor all kleen from inside out!"
"With all due respect, officer, this vehicle is perfectly street legal. I thoroughly read the Powered Vehicle Manual and there is no question whatsoever; if it were against the law the letters in the Manual would not have been printed backwards."