Posted by: safedriver | October 8, 2009

How often should you check your mirror?


From the September/October edition of The Driver magazine:

When I first started to write my regular driving column, I had to come up with a catchy title for it. After some thought, I came up with “Through My Rear View Mirror” since a lot of traffic is seen through the mirror. Up to this point, I haven’t really addressed mirrors, so let’s take a look and reflect on them now.

When I’m teaching students to drive at Young Drivers of Canada, I show them when and how often they should check their mirrors. How often do you think you should check your rear view mirror? Would you believe checking the rear view mirror every 5 to 8 seconds is ideal? It’s true! It keeps you up to date with what’s happening behind you. If you also check your mirror before you slow down, before and after you make turns and while stopped, it will keep you properly informed with what’s approaching you from behind.

Checking the mirror has a lot to do with short term memory. If you glance in the mirror, do you really remember what you saw? Do you use it to see who may be coming up beside you as well? For example, the driver you just saw in your mirror who is driving in the next lane from yours may be entering your blind spot. Once you check your mirror again, you need to recognize if they aren’t visible any longer. Where did they go? Did they turn off that road, or are they hidden within your blind spot? Short term memory needs to be used so you can remember what you saw and respond accordingly.

Many people forget what they’ve seen in their mirrors. I’ve tested this theory many times with experienced, licensed drivers; not just novice drivers. After I’ve noticed the driver checking their rear view mirror, I cover it up with my hand and ask them what was behind them. More times than not they couldn’t tell me, and they often looked into their side mirror to answer my question. Why couldn’t they tell me right away? Why did they check their mirror if they didn’t get any information from it?

Improving your short term memory is very important if you’re going to use the mirrors more effectively. There are many cognitive training programs out there that can help you improve your short term memory and remember more things while driving. I think it would be a good investment of time and money if each driver improved their cognitive skills.

Having the side mirrors angled so you can see down the side of your vehicle can also help you leave a parked position. If you’re parked on the street and have a large vehicle parked behind you, your rear view mirror is useless as all you can see in it is the parked vehicle. If angled correctly, you can use the side mirror to see if there’s a vehicle approaching from behind. This will give you the needed information to pull away from the curb safely. Having the mirrors angled much further away from the vehicle won’t allow you to do that. ( )

If you’re stopped in traffic and have a larger vehicle stopped behind you, it can make a rear crash difficult to avoid. The large vehicle would completely fill your rear view mirror and you wouldn’t know if you needed to move out of the way. Having the side mirrors set up to see a sliver of the vehicle, and set at eye level, will also allow you to see if another vehicle is approaching too fast behind that larger vehicle; thus giving you the information and time needed to avoid a rear crash.

I’ve taken licensed drivers out for re-training for many years in order to give them feedback on their driving skills. Some drivers do check their mirrors within the 5 to 8 seconds, while others need to improve the frequency of their glances. Maybe they thought it was every 5 to 8 minutes! They would check their mirrors to check to see if their hair or make-up was still looking good, but not to check up on the traffic behind them. What did they think the mirror was really for anyway?

After completing a turn is also a good time for a mirror check. I’ve seen drivers make a turn onto a busy street with other drivers approaching quickly from behind them. If they checked their mirrors immediately after turning, they would see the drivers approaching from behind and could respond by speeding up to avoid slowing down the traffic flow. Using the information that is seen through the mirror is equally as important as checking the mirror. Why check the mirror if you aren’t going to use the information as a driver?

My suggestions would not only help you, but help the other road users around you. It could also help you improve your image! 


  1. […] recently written an article for The Driver magazine outlining when the mirrors should be checked ( ), but here’s another debate to bring up; mirror set up. How should the mirrors be set up to […]

  2. My experience is that the interior mirror should be checked once 5 seconds and the relevant side mirror – once every seven seconds.

    Now, as far as how the mirrors are aligned, we seem to disagree. It’s true that adjusting the mirrors as to see the quarterpanel of the car provides a good reference point and also allows to see directly to the back through the side mirrors, but it also creates considerable blind spots, increases glare and reduces the orientation of the driver because much of the information in the mirrors is superflous and overlapped in the three different mirrors.

    The method as I’ve learned it (and instruct it) is to open the mirrors further as to not see my own car at all, and than a bit further than that. Most cars have a smaller right-side mirror, in which case that mirror should be opened further out. The idea is to generate a wide enough field of vision in the side mirrors as to cover the blind spots at 7 and 4 O’Clock around the car. These are areas which are crucial for overtaking or switching lanes.

    When opened this far, the mirrors provide so wide a coverage so that any car (or even a bike) that will be one lane away from us to either side – will be seen in at least one of the mirrors at all times, untill it becomes noticable in our peripheral vision alongside us. This results in the elimination of any effective blind spot around the car!

    Another advantage is that this angle reduces glare so that following drivers with high beams don’t reflect in the side mirrors unless they are passing us, thus they cannot dazzle us through the interior mirror, and only dazzle us temporarily (if at all) through the side mirrors when they pass us.

    The last advantage is that the overlap between the mirrors is reduced to a minimum (but not eliminated!) so that we only see the relevant information in the mirror, no unnessecary “extras.” Also, if there is any particular need to get a glimpse at our own car (such as in parking or when we need to look behind us in the side mirrors), we can simply tilt the head slightly to see it.

    It’s a bit strange to not be able to see that “silver” in the mirror, but it’s something that one can grow used to within a matter of three weeks or so.

    • Thanks again for your comment. The most common type of collison reported is a rear crash; not a side swipe. If the side mirrors are aligned to see down the side of the vehicle, the driver can see past the large vehicle sitting behind them. This means they can see if the second vehicle is slowing enough. If they aren’t, they’ll have a chance to move out of the way. Checking your mirror every 5 to 8 seconds also means you’ll need to use your short term memory. This will keep you up to date of who’s entering your blind spot. Mirrors need to be set up for the driver’s advantage, not just for convenience.

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  4. Most people agree that we should check mirrors frequently, but needs slight clarification. I think you need to check mirrors if you are approaching a situation where you may need to change your status on road, ie change your speed or position on the road.

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  6. I have a question which falls in this general category: When should you NOT dim your rear view mirror? I only dim (darken, flip) the rear view mirror on unlit country roads when headlights behind me can be blinding. I don’t dim the rear view for city driving, because it cuts out too much detail and headlights in the city aren’t blindingly bright. What is the “official” way, and/or does it really matter in the city? PS. Great column, thanks!

    • You should never dim the rear view mirror when there’s no need for it. Other than when the driver behind has their high beam’s on, there’s really never any other time. The only exception would be if your vehicle is a little lower to the road than the vehicle behind and their headlights are directly in the path of your rear view mirror while stopped (ie: a large truck). All other times you need a good view from the mirror. Thanks for the comment and thanks for reading!

  7. I think you need to check mirrors if you are approaching a situation where you may need to change your status on road, ie change your speed or position on the road.

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