I am a long time bicycle commuter (now retired) and I did the TransAm bicycle route (east to west) in 2005. While commuting and in all other riding that I do, including the cross country ride, I find my glasses-mounted, flat, 1 inch or so rear view mirror to be almost indispensable. Combating a stiff neck is certainly one one reason I like it. Even so, I will not pull a lane change or move out into a traffic lane without glancing back first with my full vision and a real head turn. When I do a lot of cycling, as I did before retiring and while on the TransAm, I find I wish I had the mirror at many other times, too. While hiking, or just walking for instance.
Some reasons I like a glasses-mounted bike mirror:
1. No false positives: If you could have a medical test that never gave you a false positive in indicating a potentially serious disease, would it be worthwhile to have it? I think so. No matter how you misuse a rear-view mirror, if there is a car visible in it, you have one more piece of information about your environment that you can use in your effort to continue on your ride safely.
2. Wide view of what’s behind you: A quick sweep of the head, about what you would do if you didn’t have a mirror gives you a look all across the road behind you, including the area to your right. Your normal quick view can be done with about a 45 deg turn of the head for the kind of mirror that I use. This should be enough to alert drivers, because they will see your head turn. With the kind of mirror that I use, estimates of distance and speed are not as severely impaired as with a convex mirror such as the ones usually mounted on a handle bar.
3. Easier to use your hearing as an indicator of traffic coming from behind: Hearing is another sense that does not produce a false positive: If you hear a car or truck, it is really there. Don’t trust a negative result, though: those hybrids are real quiet. I find a quick mirror check just after a car passes to be very helpful in knowing if there is a vehicle coming up from behind that you either didn’t see or can’t hear because of the passing one.
4. Just as when driving a car, the continual awareness of traffic both front and behind is important: I cannot see how the various arguments about possible misuse of a mirror while bicycling would be any different if applied to driving a car. For instance: some say that “Scanning a mirror can be a distraction from the more urgent task of scanning the road ahead of you.” But that can equally apply to those driving a car. Some of the mirrors drivers use are convex and therefore “Objects are closer than they appear.”
I don’t believe you can effectively use binocular vision when looking sideways from both eyes as you must do when looking backward while turning your head. Think about it: your eyes are looking as far as they can to one side; draw a picture and note how effectively close together they are, thus reducing your binocular distance estimating ability. Why would one think that a mirrored cyclist was concentrating in the wrong direction any more than you would feel that a mirrored driver was doing so?
As I stated above, my use of a mirror still requires me to turn my head, though not as far as I would to get a full view with both eyes. I invite you and any other rider who doesn’t use a mirror to check some time just how often the rearward glance actually provides a look with both eyes directly behind you. Since I still have my peripheral vision and the mirror only covers a small solid angle of my visual field, I do not feel my forward vision is seriously compromised. As far as judging closing speed, I’m convinced that the bicyclist with a flat mirror will be judging it the same way as a driver, by how rapidly the approaching vehicle is changing apparent size. Check in a car sometime and see just how often you are looking at an object in your mirror with just one eye.
I had the opportunity to observe riders on the TransAm who didn’t have mirrors and who, because they were otherwise not paying attention, were surprised by vehicles approaching from the rear. This surprise can be evidenced by a startled reaction or by not being prepared for a gust of wind. I, personally, ride differently when a car is overtaking me: I make every effort to keep a steady path or make very gradual changes in path; I will check ahead of me to see if an overtaking vehicle is about to meet an oncoming car so that I can be prepared for a closer approach than if there is none; I make sure I am not pressing a button on my cycle computer or taking a drink of water; I won’t stretch my legs or my arms.
To sum up my position: I want as much information about my environment as is possibly available to help me make decisions about how I am going to approach the many situations that arise while cycling (or doing anything else in life). The little mirror attached to my eyeglasses provides some of that information and is well worth the little bit of fussing around and understanding of its limitations that is required to be a safer rider.
Jim Hammond lives in Sisters, Oregon at the intersection of the TransAm Bicycle route and the new Sierra-Cascades route being mapped by the Adventure Cycling Association. This summer Jim and a few friends will be riding the new route from Canada to Mexico.