Mirror, signal, shoulder check, change is the chant that we all know to follow for a successful lane change. We also use our rearview mirrors to give us a better view than our eyes alone when we are backing up. Is this all that mirrors are used for and are these the only times that we use them?
Most of us do not give the rear view mirrors the attention that they deserve. A defensive driver will scan ahead to see what they are approaching, to the sides to see what is around them, to the rear to see what is behind and finally check the instrument panel to monitor their speed and vehicle condition. This cycle repeats every five to eight seconds, so their mirrors do get a regular workout.
The rearview mirror must be consulted before you put your foot on the brake. This may be the only way to decide if you will be hit from the rear if you slow or stop. Being aware of vehicles following you too closely or overtaking you too quickly may make you change your mind about braking or show you that you need to take evasive action.
One last thought concerns moving back into the lane after passing an overtaken vehicle. You should not do this until you can see all of the vehicle you have passed in your rear view mirror. Failing to do this will put the overtaken driver in the position of unintentionally tailgating you.
Reference Link: http://www.drivesmartbc.ca/skills/using-your-rear-view-mirrors