February 15, 2008

Driving Safety - A Tip For Making Traffic Useful

I read a rule of thumb somewhere that if you have your sideview mirrors adjusted correctly, you should not be seeing the side of your car in them. I have an even better tip for getting your side mirrors optimally adjusted.

If you find yourself in heavy traffic, the kind where you are rolling very slowly, it’s a great opportunity to test your mirror configuration for blind spots.

Ideal mirror positioning means that no matter where a car is in the lane next to you (either side), you should be able to see it in a mirror or through a window without moving your body or turning your head. That way you can keep your eyes primarily on the road, and either see nearby cars with just a glance, or with your peripheral vision. If you have to move your head to see a car, or you can’t see it no matter what, the car is said to be in your blind spot.

You can get by with blind spots because often a car moves into a blind spot after you are already aware of it, and then it exits your blind spot. You will have a continuous awareness of this car because your brain knows that cars don’t cease to exist just because you can’t see them. However, this is far from ideal, and it is also possible that a car can get close to you while staying in your blind spot, never becoming visible at all. Merging into traffic is one situation that can cause this problem to arise, because the angle of your car changes with respect to your direction of travel.

In any case, it’s best to minimize or eliminate blind spots. Here’s my suggestion:

  • In heavy traffic, find a car you are near that is passing you slowly, or is being passed by you, slowly.
  • Notice when it passes through your different visual zones:
    • visible in your rear-view mirror
    • visible in your side view mirror
    • visible through your side window, peripherally
    • visible through your windshield
  • Ideally, you should never be able to lose sight of the car as it moves through these zones. If you do lose the car, you have a blind spot.
  • To eliminate a blind spot, you would usually want to adjust your side mirror so that it is tilted more away from your car. If you have motorized mirrors, you can make the adjustment and try again immediately. If your mirrors must be manually adjusted, you will have to wait until you are parked, adjust them, and then check them again later.
  • Vertical tilt doesn’t have as much of an effect on your blind spot, but you may want to make small vertical adjustments if you notice you are looking over the tops of cars, or seeing too much road.
  • Repeat until your blind spots are gone.

If you can’t get rid of your blind spots (and you may not be able to, especially on your driver’s side mirror1) consider getting a small, round, convex mirror with an adhesive backing and affix that to your driver’s side mirror. My thoughts are that it’s best to affix it in a spot that is closest to where your blind spot happens, but YMMV.

With correctly-adjusted mirrors, you’ll be a safer driver. And I know I’m more relaxed when I’ve eliminated my mirror blind spots.

1 The passenger side mirror on most cars is already a convex mirror, which is why those mirrors usually carry some warning about the distortion of perceived distances in the mirror.

Posted by James at February 15, 2008 3:03 PM
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I have my mirrors adjusted like this. It drives my wife NUTS that she can't see the side of the car. I've tried explaining to her that she doesn't NEED to see the side of OUR car, but that falls on deaf ears.

Posted by: Bob McCown at February 15, 2008 4:29 PM

I've never heard of anyone getting into a collision with the side of their own car while they were driving it.

Posted by: James at February 15, 2008 4:35 PM

Here's Click & Clack's version:
I haven't yet had the guts to try it (I'm worried about the "it takes some getting used to" part), but when I posted it on my blog, some readers said they'd done it and it really works.

Posted by: Karen at February 15, 2008 4:45 PM

Thanks for that link - they're description is nice, with the illustrations.

I think doing it in slow-moving traffic is safer than trying to do it while someone is passing you at a high speed differential on the highway, or when you're both traveling at high speed. You need your full attention on the road, especially when you're moving at a high rate of speed.

You might even be able to do it in a driveway and have a helper walk past your car, but since people are smaller you may feel you have a blind spot when you really don't.

Posted by: James at February 15, 2008 4:54 PM

I'm not worried about crashing into the side of my own car, but I did have a problem with an old car where the mirrors sometimes mysteriously (actually, not very mysteriously) got "adjusted" overnight while in the apartment complex parking lot. (No, some people do not have better things to do with their time.) Without the very edge of my car as a reference point, I couldn't tell right away whether the mirrors were out of whack or not.

It's less of a problem now because they're adjusted electronically from inside the car. You can't adjust them just by pushing them; you'd probably break them. However, some older/cheaper cars probably still have the kind that are adjusted manually.

Posted by: Julie at February 15, 2008 6:44 PM

Unfortunately, if you're concerned about blind spots then you'd be trading away proper mirror alignment.

But at least that's a plausible reason to want to have the mirrors set up that way. You could thwart your tormentors somewhat AND keep your mirrors better aligned by placing a bit of tape or some other mark on parts of the mirror assembly, lining up with the "correct" angle of the mirror, to see if they had been messed with. It might not help you quickly re-adjust them, but it would tell you quickly if they'd been sabotaged and might help you get them close to realigned.

Posted by: James at February 15, 2008 7:29 PM

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