You need to put a “Smartcar” in the bed of the truck with a license that reads “SPARE”.
We figured it was an RV's towbehind, but no - a gray haired lady came out of the restroom, hopped in and headed east. We caught up with her a few miles down the road as a semi was passing her in the left lane -- her little ride got a definite case of the wobbles during that maneuver.