as a class A driver for over three decades.
never trust your mirrors.
keep your eyes open as to what is behind, to both sides of you... as far as you can see. take note, red small ca, white full sized truck, etc.
keep a mental note of where they are and should be.
it takes 100% of your focus to do this.
if done right then you can trust up to a point what you can see.
if parking get out and look as many times as you want. tell onlookers your just having fun with them.
i have driven trucks with as many as six (yes 6) mirrors on just the rt side of the rig. and still can not see every inch of the rt side. let alone everything in that lane, then there are these fools that go zoom-zoom. around you.