hen Nick Simons took the three-wheeled Slingshot out for a test ride this summer on a scenic country road in Warren County, he passed a group of three motorcycle riders driving in the opposite direction.

The third rider gave Simons the universal "motorcycle salute," a slight, down-low wave of the hand.

"See, he knew this is a motorcycle. A lot of people don’t know it yet," Simons said, after he waved back and returned his...