[The Toad]

Pretty much unnecessary if you know how to adjust your side mirrors properly. I've a number of cars and I've never had a problem adjusting the mirrors to get rid of that blind spot.

Driver's Ed teaches people to sight the side mirrors along the side of the care, but that is incorrect. They should be adjusted to remove the blind spot.

It is a solution looking for a problem....

[The Toad]

I adjust mine so that the side view mirrors “extend” the view based on what the rear-view mirror doesn’t/does show. Problem solved. I don’t know why it isn’t taught properly.