What is a blind spot and where is it located?
A "blind spot" it’s an area around your vehicle that can not be observed in any mirror. Any vehicle has at least two"blind spots". Usually if another vehicle, cyclist or pedestrian located near a back quarter of your vehicle, you wont be able to see it in any of your mirrors (side or rear view). I have a small example below:
Black vehicle just a little ahead of me and white minivan (in a side mirror) is right behind me. We do not see any other vehicle in a mirror or in a window right beside.
When I turn my had slightly back and check a rear quarter of my vehicle this is what I see:
Since you where not in a vehicle at that time with me, you may think it is not a true, but if you look at the first picture again, you will see I have little circle mirror on a corner of my side mirror. This little mirror called a "blind spot" mirror, and if you look carefully you can see this white Mazda is right there.
Now for a moment imagine: I do not have this “blind spot” mirrors and I decide to change to the left lane, and did not check my “blind spot” by shoulder check. I check only side mirror and I did not see this car in my “blind spot”. :-(
I will recommend you: Always do your shoulder checks, even if you have your blind spot mirrors. I hardly believe that you will pay 100% of your attention to the road while you drive, and you will scan all your 5 mirrors (2 side mirrors, 2 "blind spot" mirrors and rear view mirror) every few seconds.
Learn How to do a shoulder check correctly.
Never drive in a "blind spot" of another vehicle. Remember that big vehicles, like commercial trucks, have more than 2 blind spots and their blind spots are huge. Never drive side by side with another vehicle for too long time. Pass it or stay behind it. Be smart and protect your self from other people mistakes.