Saw this picture of a second gen Nissan Cube with fender mirrors and thought it looked rad. But it made me wonder if there were any laws stopping the average person from installing some fender mirrors on any car they wanted here in the US. It seems that, as long as you have mirrors, they're legal. For my state:

New Jersey

Added: 4-28-09 Regulation: 39:3-71.Mirrors

Every motor vehicle shall have rear view mirrors so located and angled as to give the driver adequate rear view vision. Every passenger automobile manufactured after January 1, 1965 and registered in this State, shall be equipped with an interior mirror and an exterior mirror on the driver's side. On and after January 1, 1965, every commercial motor vehicle registered in this State, other than a trailer or semitrailer, shall be equipped with an interior mirror and an exterior mirror on the driver's side, except that every such vehicle so constructed or loaded as to obstruct or obscure a rear view from an interior mirror shall, in lieu of an interior mirror, be equipped with an exterior mirror on the side of the vehicle opposite the driver's side. The director may by regulation establish other mirror requirements for special or unusual types of vehicles. Any person operating a motor vehicle without the equipment prescribed by this section shall, on conviction, be fined as provided in Revised Statutes 39:3-79.

Amended by L.1964, c. 119, s. 1.

Here's a state by state list.

So if there isn't any law preventing cars from having wing mirrors, why aren't car makers just using them from the factory? They certainly look 10 times better. The obvious answer is that car makers have strict rules for pedestrian safety that prevents wing mirrors from being utilized. Is there also some aerodynamic downside though?