If he shows no signs of impairment, why are the test even being administered? A lot of people think that they can be convicted anyway, or they can be prosecuted anyway, but in the question itself it said, "The driver shows no signs of impairment." Signs of impairment are weaving with outside of your lane of travel, running a stop sign, or running a red light. So, they might get indicators of impairment before they even approach your window. Usually, if they pulled you over for an expired tag, guess what? That's not a sign of impairment, and if the person doesn't fumble with their license, they can divide their attention, they don't smell like alcohol, they don't give any other indicators of impairment, then the officer's really not allowed to go to that next step and make them take tests. So, refusing all tests is what I advise everybody to do, no matter how much you've had to drink.