Rear view mirrors are an indispensable accessory when driving any motor vehicle and since their use in all cars, there is no standard way of adjusting them. Most drivers adjust the rearview mirror to encompass the rear window of the car and this is generally an acceptable way of doing so. Some drivers though will bias the side-to-side angle of the rearview mirror so that a very small portion of the rear windshield trim is visible. In the case of left-hand drive cars, this would mean that the rearview mirror would be angled slightly to the right. The majority or drivers will adjust their side-view mirrors with what we will call the narrow-angle view. This means that a fourth of the usable area of the mirror will show the side of the car being driven. This is done for the left and right side-view mirrors.
There is a school of thought though that promotes the wide-angle view. The theory is that this setting will eliminate the blind spots in your view to the rear. A car coming from the rear will first be seen in the mirror mirror and as it moves past your vehicle, that particular car will instantly show up in either the left or right side-view mirror. Although it may seem like a new method, this teaching has been around since the late 60s but has not really done on because it is disconcerting for the first few times that you try it out. Here are the steps to set your mirrors to a wide-angle view.
1. Set your rear-view mirror in the normal way.
2. Lean your head all the way to the left so it Touches the driver's window. Set your left side-view mirror so you can see the back corner of your car.
3. Lean in the opposite direction at the same distance and set the right side-view mirror as in step 2.
Set this way, you will have eliminated the blind spots in your car.
There are, however, vehicles with convex mirrors installed in them that give a wider view despite being adjusted in the traditional way. This mirrors have a fault dotted line in the outer third part which is angled, thus showing a wider view to the rear. However, not all cars have this type of side-view mirror since it is more expensive to produce.
Another mirror adjustment that is used involve the side mirrors pointing at the car's blind spots on the sides. They are tilted in combination with the rear view mirror so that as soon as a car moves close enough to the rear of the car where the headlight can not be seen, the car becomes visible in the side view mirror. Basically drivers side + rear view + passenger side mirror are lined up to act like single wide angle mirror. The side mirrors are used to check the sides of the cars, not the rear.
What all these adjustment advice do not teach is that the driver must have, or develop, the situational awareness necessary to be a safe driver. You have to check your mirrors regularly and most specifically when you are making a turn or lane change so that you are aware of objects and vehicles not only in front but also behind you. No amount of adjustment or gadgetry can compensate for dumb driving habits.