With proper mirror adjustments you never have to worry about not seeing the car next to you when changing lanes. This is how it goes:

Sit in your car seat and rest your head all the way against the headrest or seat for that matter. Now for the left mirror, turn your head as far as you can to the left looking into the mirror. Adjust your mirror to where you can just barely see the side body of your car. Repeat this proceedure for your right side. It may feel awkward at first but you will get used to it. You will notice as cars pass you or vice versa, that by the time you do not see the vehicle in the mirror anymore, you see it's nose looking out the side window. I have done this for a long time and never had a problem making lane changes. I pretty much pretend in my VX that I have no rear window.