What I can't understand is why many manufacturers, including BMW, have skimped on the size of the outside rearview mirrors, or have made them in such odd, even ridiculous shapes, that relying on them is pointless. Prior to getting my E36, I drove an E21, which had a wonderful "greenhouse" for visibility, and mirrors so amply sized I used to joke (among a select audience) that I'd like to take them off the car sometimes and put them on the bedroom ceiling. The point is they gave a wonderful angle of view, and I didn't have to turn my head while making lane changes, the information I needed to know to make the maneuver could be gleaned from a look at the mirrors.
Not so with the E36, it was one of the first things I noticed about the car, BMW skimped on the size of the outside rearviews, and I now make it practice to turn my head to check around me before making even routine lane changes, and I certainly try to avoid situations which might require a sudden lane change, when a check of the mirrors may not be enought and there isn't the time to turn the heard. I've noticed it's particularly dicey when entering highways off an entrance ramp, a quite sizable blind spot exists, and extra care needs to be observed to get on the highway safely.
This is one area where I think regulations are required, assuring drivers ample rearward vision, rather than allowing diminutive mirrors, and stupidly shaped ones as well, such as ovals and trapezoids which cut out significant portions of the useful field of view. How and why manufacturers were allowed to get away with this I can't figure, it really is a safety issue.