Let’s face it; we tend to look at ourselves in the mirror. It’s not really about being vane. It’s more like wanting to know that you look presentable without having any food still stuck in your teeth. Some people check the mirror to see if their hair is still looking good. I don’t have that problem any longer. But there’s still another reason to look in the mirror, especially while driving.
Many drivers check their rear view mirror as they drive but maybe not often enough. A good way to determine if you’re checking your mirror often enough is to count between checks. A good measurement is checking your mirror between 5 and 8 seconds. Some people say 10 seconds is good too. That’d fine, but to judge that time you should count to yourself and make a conscious decision when to check your mirror. This time frame is roughly one city block. And you may be asking; what could go wrong in one city block that makes me need to check my mirror? Good question.
For each block you travel you’re also going through intersections. After checking your mirror, a driver may pull out from that intersection and approach you from behind. Checking your mirror often will keep you up to date with what’s happening behind you. You’ll also be able to tell if the vehicle behind is gaining on you. When I ask my students that I’m teaching at Young Drivers of Canada, they’re pretty good with knowing that the image of the vehicle behind gets larger in the mirror if they are gaining on you.
Other times to check your mirror would be before and after turning. You want to see if a cyclist is coming up on your side before you make a turn. Perhaps another driver is trying to sneak beside your vehicle to make that same turn. Checking the mirror after the turn allows you to see what’s behind you, now that you’re on another road. One of the least times many drivers check their rear view mirror is while stopped. Most drivers tend to look around at most anything… except the mirror. If you need to move out of the way for an emergency vehicle or to avoid a rear crash, you’ll need to check your mirror often while stopped.
culled from http://safedriving.wordpress.com/