How to correctly set your car’s sideview mirrors

When I first started driving, like most people I know I set my sideview mirrors so that I could always see the side of the car. It seemed like the right thing to do. However, this leaves one with a huge blind spot, especially just off to your back left. At the time, I figured you just had to turn around to properly clear yourself before changing lanes, and I didn’t understand why we even bothered to have sideview mirrors. Fortunately, not long after I got my license, my insurance company decided to put a little set of instructions in their monthly newsletter for young drivers on how to properly set the mirrors. It turns out the car companies actually know what they’re doing with the whole mirror situation, it’s just that most of us don’t. Here’s how they’re supposed to work:

The problem with the way most people set up their mirrors is that they render the sideview mirrors almost completely redundent with the rearview (center) mirror by aiming them essentually straight back, so that you can see what’s pretty much straight behind you, including the side of your car, but not much to the side. But the sideview mirrors are actually supposed to cover very little: just the area between what you can see out the back with the rearview, and what you can see with your peripheral vision. With properly set mirrors you should be able to see everything without moving your head. You should be able to see a car coming from behind you in either lane in your rearview mirror, and as it leaves your rearview mirror it should be just coming into your sideview, and as it leaves your sideview mirrors it should be coming up directly beside you in your peripheral vision. You should thus be able to change lanes by moving your eyes, not your head.

Given differences in people’s cars (not to mention heads) the only way to get it perfect is to experiment, making sure that you never lose complete sight of a car passing you on either side. You can do this safely while stopped at a light as cars pulls up beside you, or you can adjust them while parked on the side of a street. To get a very good first approximation, do the following (this is the method USAA recommends):

  1. Set the rearview so that you can see straight backwards.
  2. Stick your head up right against the driver side window, and adjust your left sideview mirror so that you can just begin to see the left side of your car.
  3. Put your head in the middle of the car, between the driver and front passenger’s seat and adjust your right mirror until you can just see the right side of the car.

When you are in a normal driving position, you won’t be able to see your own car in your sideview mirrors. You’ll probably find driving like this disconcerting at first because all you can see on the side mirrors is the side of the road rushing by, with no visual reference to let you know exactly where you’re looking. In fact, you won’t be able to see anything in your sideview mirrors that you can see in your rearview. But that’s the point! If they are adjusted correctly, each mirror handles a certain angle of view behind you such that everything is covered, with no blindspot big enough for a car.

When changing lanes, all you need to do is check your rearview, and then glance to the appropriate sideview to make sure it’s not filled with car. If you just see a blur of road rushing by, you’re clear. It takes a while to learn to trust it, and for me the only way I could do so was to verify several times that I never lost sight of a passing car as I was driving.

Unlike most of my posts, this isn’t just meaningless pedantry. The whole idea is that if you have your mirrors adjusted correctly, you never need to turn your head around to change lanes, thus always keeping your head pointed where you’re going. Turning around to check what you might bump into while changing lanes is really a bad idea when it leaves you not looking at what you’re headed towards at 65 MPH.

43 responses to “How to correctly set your car’s sideview mirrors”

  1. While I disagree that most of your posts are meaningless, this one is definitely helpful in a different way. You lost me, though, on your explanation of the convex nature of the right mirror, and not just, I’m pretty sure, because I didn’t know what subtend meant. I’m still working on understanding that part.

    I’m planning to try out the repositioning though, and at once was intrigued by and enjoyed the images of pushing one’s face up against the window and then bobbing it in the middle of the car there to get a starting place for the mirrors. Imagine how much disaster this could avert.

  2. Hi Mere,

    I know I didn’t explain that well. I really should add a couple of pictures to this post, but I’m too lazy. By subtend, I just mean how big the right side mirror appear to be from your vision. If you drew a triangle with one point at your eye, and the other two points at the side of the mirror, it would be a smaller angle for the right mirror than the left (since it’s further away). They have to make up for this by “fanning in” the rays of light coming in to the mirror, so that you, in effect, see much more out of the right mirror than you normally would. Probably an intuitive idea that I’ve made hopeless complicated by trying to put it into words.

    Good luck with the new mirror positioning. You’ll probably find yourself changing lanes like mad now that only your eyeball needs to move. Proper mirror positioning is absolutely essential for any self respecting Masshole driver. I haven’t let a single New Jersey driver pass me yet.

  3. Jonathan,

    Thanks. I’ll actually try this next time I drive.
    It’s funny how many things that seem patently obvious once you hear about them escape us for so long.

  4. All well and good…but do you have to go through this rigamarole everytime you enter the vehicle. How does one confirm their mirrors have not been bumped?

    I’m sticking with my mirror check and quick backwards glance upon merging….

    Not that I have a rear view mirror or left mirror anymore.

  5. I first learned about how to adjust your sideview mirrors from the AARP Magazine. Both of my vehicles have their sideview mirrors adjusted as you have discribed. Whenever I purchase a new vehicle, the first thing I do is to set the sideview mirrors, as I have found that I do not have any blinds spots with them adjusted properly.

  6. I did it, and a car passed me on the highway, and it was AWESOME!!! But then I went to pass someone and still glanced to the left…

    • It is a nice presentation, but it’s wrong. It has you setting the mirrors too close in. Also, while the picture looks nice, it’s clear that it wasn’t done accurately, as both mirrors are shown to cover the same visual angle.

  7. Great article! I’ve been using this method for some years now. But on multi-lane highways I think there may still be blind spots — For example, suppose there are 3 lanes in your direction, and you are in the right-most lane — If a driver in the left-most lane (and to the rear of you) suddenly cuts across two lanes to try to pass you, he might enter a blind spot when he leaves your rear view mirror.

    Also on curves and onramps the angles are different and there may be blind spots.

    Love to hear you comments on these situations!

    • Thanks for writing! You make a good point. I agree somebody two lanes over can be in a blind spot, because the size of the blind spot increases as you go away from the car. (Because it’s really more accurate to say there’s a blind range of angles at which you can’t see anything.) However, I’ve given it some thought, and the fact still remains that once a car is close enough, you should see them. Well before you would hit them.

      However, you may have a good point in that if somebody flies across lanes quickly enough, you won’t have enough warning. I can see how turning around to make a quick check would be helpful here. And it certainly is further argument why you should make slow lane changes.

      On the other hand, if you’re turned around, you’re missing what’s coming at you from ahead and the other side. Even if you turn around for one second, you’ve covered over 100 feet of road while you weren’t watching. No matter which way you look, you’ve always got a blind spot, and somebody could always do something quickly that will get you. So, my feeling is you want to minimize the blind spots looking forward, and keep watching the road. But I’m no authority, and I’d be interested to hear your, and other people’s, thoughts on this.

  8. hi very good article and have forwarded it to my son who has just passed his test… All I know is if some-one has been driving my car and altered my mirrors I have a tendency to orbit.. Well done and keep up the good writing.

    • I agree with Car Hire Bristol Airport, this method doesn’t let you see bikes and motorcycles. I think it’s better to turn them in a bit further, and turn your head to cover the blind spot. If you’re too close to the car in front to safely turn your head for an instant, you’re too close to be changing lanes.

      Why don’t they just make side mirrors bigger? Looks funny?

      • I disagree. The fact that a motorcycle is smaller doesn’t really matter. For one, it’s not much smaller in the axis that matters for blind spots: length. Second, you can adjust your mirror so that a given SPOT on a car is always in view in at least two mirrors. Thus, it would be impossible for anything to hide, car, bike or human. If it was really neccesary to turn around to check your blind spot, don’t you wonder why they bother to put side view mirrors on cars? Is it just to screw with us? They do it because the people that design cars know that the idea of a blind spot is a myth.

        I also disagree that turning around is not a problem. Turning your head for an instant is meaningless. You need to turn around for at least a second to really see. And then it takes around a second for your eyes to settle back on the road ahead. Again, if turning around were a good idea, cars wouldn’t have side view mirrors! A lot can happen in a couple of seconds when going 65 MPH. You should be looking where you’re going, not behind you.

        • The problem with seeing bikes and motorcycles is not just that they’re smaller, it’s that they can be close to your car, hidden behind the rear pillar. You can’t see there with the main mirror and you can’t see them with the side mirror if it’s aimed out too far.

          • I’m not sure I understand. If they are hidden behind the rear pillar, how are you going to see them by turning around? I should probably just make a diagram for this post, but my understanding is that the volume of space in which something can hide with properly adjusted mirrors is very small (much shorter than the car) and pretty much right on top of your car. Perhaps you could fit a motorcycle in there. But if somebody is riding a small motorcycle a foot away from my car, that’s their problem, not mine…

        • In this country (Australia) if you don’t do a head check when you change lanes in your driving test, you’ll fail. Whatever position your mirrors are in, you still need to do it.

          Of course this means you’re not looking ahead for half a second. My philosophy is that if you’re so close to the car in front that you can’t look away for half a second then you can’t change lanes. Perhaps in your country the traffic density is such that you’re too close all the time.

  9. While your article wasn’t how I learned of this mirror setting methodology, it was one of the first hits when I searched on ‘properly set automobile mirrors’.
    I was looking for a good online guide to setting vehicular mirrors that I could forward to my company’s (major electric & gas utility) safety department so they could review and get the word out to the rest of the employees. I think that setting the mirrors as you recommend dramatically increases the situational awareness of the driver, virtually eliminating the need to turn one’s head.
    My father turned me on to this method just a few months ago after I was involved in a minor accident that was a direct result of me turning my head to visually check a blind spot. While travelling at highway speeds at a safe distance from the car ahead of me, I turned my head to the right to check a blind spot. Unfortunately for me, right as I had turned my head the car ahead of me braked hard. When my focus was back to the road ahead of me I realized my predicament and fully applied the brakes (couldn’t change lanes due to traffic). Since I had been following at a safe distance there was still enough time to bleed most of my car’s speed to the result that I only scratched the bumper of the car ahead of me. If I had the extra 1+ seconds of reaction time that I lost by turning head, the collision would have been avoided.
    Again, I think that the information that you are providing is excellent and is potentially life-saving. The only thing that I would change is this: I’d add a reference to SAE paper 950601 “The Geometry of Automotive Rearview Mirrors – Why Blind Zones Exist and Strategies to Overcome Them”. It backs up the information provided by a single person with the weight of a global association of more than 138,000 engineers and related technical experts.

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  16. Turning your head and checking a lane is something you should be doing anyway, so adjusting the mirror for that is silly – plus it’s in your own self interest, the other vehicle can avoid you more easily by slowing or swerving, they get a warning (your turn signal), they’re protected inside their car, and they have nice loud horn to warn you. A cyclist has none of that, save maybe, if they’re lucky, seeing you inside the car getting ready to step out.

    A driver has zero self interest (aside from the lawsuit and fine) when it comes to not dooring cyclists, who are the most vulnerable users of the road. So, yes, I do think you should adjust your mirror for it.

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