A lot of people have blind spots because they do not have their mirrors positioned correctly. If you can see the back corners of your car in your normal driving position, then your mirrors are aimed too far inward. You should only be able to see the back right corner of your car in your right mirror when you are looking with your head in the middle of the car. You should only be able to see the back left of your car in your left mirror when you are looking with your head almost touching the window. It takes some getting used to, but it really eliminates the blinds spots for free.