Saturday, September 8

Stepping Down the Pyramid with Mirrors

My Own Dear Departed Mirror
In the last couple of weeks, I was prompted by a couple of events to think again about mirrors when using a bike. Namely, how might mirrors help a cyclist reduce unsafe ("at risk") behaviors; which are the base of the safety pyramid. Some of those behaviors belong to us cyclists. Other unsafe behaviorsbelong to our motoring companions. It isn't always easy to separate the former from the latter. To REALLY be safe, we need to find ways to reduce both.
The Safety Pyramid - You Want to Move DOWN IT!

The first event was a long, drawn out discussion amongst Bike League cycling instructors about mirrors. One point that stuck with me was the inquiry by Khal of Los Alamos Bikes, namely:

"Question to those who strongly advocate mirrors. How often do you check mirrors in traffic, and does this give you adequate warning of a suddenly developing situation?"

It seemed to me that most of the ensuing discussion focused on feelings and faith rather than "what do we need to do."

The second event was the rare "drama behind me." In it, seeing a motorist proceeding in the middle lane of three choices, and me planning to cross those three lanes prior to making a left, I initiated a right turn into the right lane (right turn on red). Normally, the motorist would have swept by and then I'd be up to speed and move over to make the left. I COULD have simply waited, but it seemed to be pretty simple. This time, however, the motorist swerved from the middle lane into the right lane - MY lane. What? Suddenly I was in a lane at about 10mph with a motorist directly behind, doing 50 and closing fast. I considered my options, not knowing exactly WHY this lady had swerved from a "clean and simpl pass" position into a "hit from behind" position; things didn't seem clear. As a result, I fell back on experience and hung a left turn signal while keeping close watch. If the lady was going to make a right, she'd see it and we'd be good. If she was wondering about my intent, she'd see it. Either way, I was definitely going to watch this motorist's wheels to see what would happen next. While my stress level edged up. At this point, anything other than "stay the course andO signal my intent" seemed to be a poor bet.

Well, as it turned out, the motorist then swerved left, back into her original lane, passed me with plenty of clearance (remember, I was signaling an intent to go INTO that lane she swung back into), and proceeded apace. After she passed, I exhaled, completed my leftward shifts and made my left turn; thinking about the safety pyramid and pondering how any mirror might have helped. Lest you think I'm simply being "dramatic," one of my engineers saw the event and said he was wondering if he needed to be calling 911. Lest you think I narrowly escaped death, the lady's closest approach was probably ten feet as she swept by in her original lane. I have no idea what the lady had in mind, other than she imagined I'd cross all the way across the street in front of her instead of following traffic protocol, and decided her best chance to miss the "idiot" was to swerve right. Assuming she was paying attention (she was NOT chatting on any mobile device), despite my concern, I was in absolutely no danger whatsoever UNLESS I'd done some ill-advised evasive maneuver at the last moment - mirror help or hurt? I guess my "proper" behavior simply fooled her. Who really knows. Regardless, as PM Summer once said: "no harm no foul."

Second Event - View from Google Maps - Arrows from Yours Truly
I'm neither a big fan nor opponent of mirrors. The one time I used one, it proved a useful added means to help in overall situation awareness. I think, however, that mirrors are a bit oversold, as are other safety things such as "high vis" and helmets. In the final analysis, our FIRST line of defense as road users (or on other public travel routes) is that our fellow road users know what we plan to do and what they in turn need to do to avoid disaster. That is the basis of traffic law.

Let us consider the actual USE of mirrors. Any mirror has three uses; the first is to see what is directly behind, the second is to see what might be developing in the lane to one's left when you might be considering such a shift, and the third is a similar function for a rightward shift. We'll consider them in order.

If you are looking to see what is going on behind you in a mirror, you are motivated by concerns about the general situation or you think you may want to send some message to following traffic. In the case of the "second event," what message would a mirror enable me to send? In reality, in such a situation, clear consistent operation seems to be the best principle when encountering another road user that seems to be doing illogical things. Even a wave or a "slow down" signal might confuse things for a distracted driver. What's more, for looking behind, we on bikes have no need for the "behind" mirror to keep from backing over people or stuff in the driveway. As you might see from the photo below. The rearview mirror is imperfect in that regard even in the MIGHTY LAND ROVER.

Mirror to Look Directly Behind. Mostly Useful for Backing Up
OTOH, a mirror is quite useful to look behind when one is wondering what happened to that motorist behind that should be ready to pass now. In the one day I had a mirror, it repeatedly answered such questions. No safety issue, but I, for one, dislike even short-term mysteries when riding. Score a point for mirrors.

SIDE (left or right)

LH Mirror - Aim it at the Lane to Your Vehicle's Left According to SAE
A mirror has definite uses when considering a left or right lane move in traffic. That is one reason that driver side mirrors have been required for cars starting in 1968 (prior to 1968, no side mirrors were required). They also became ubiquitous on the far (right) side of cars by the early 90's. In the case of a side mirror, it is "aimed" at the next lane over so you can see what will crunch you if you shift over. Such a mirror is clearly aimed differently than the "behind" mirror. Go HERE for a discussion on mirror aiming. Cyclists have an advantage in this regard over motorists because their head movements that effectively change mirror aiming are less than for their motoring brethren. Still, a mirror is either optimized to see behind or to one or the other sides. And THAT is a point mostly missed in the LAB discussions: if aimed behind, what action can you suddenly take that does not make you LESS predictable? If aimed to a side, how often does it really make a difference? While we are talking about SIDE mirrors, the reason RH mirrors came along much later is that they are a lot less likely to be really useful. Think about it. If you are on a bike (or in a car) and making a right turn, motorists on your right are a rare event. If you are making a lane shift to the left; much more likely. As for pedestrians, we on bikes really don't need mirrors to see them.

RH Side Mirror. Look HERE to Check Before a RH Lane Change. Objects are Closer Than They Appear!

If you are in a car, the side view mirror is much closer to the lane divider than it would typically be if you are on a bike - UNLESS you are riding a bit left of the LH tire track. This is simply due to the much wider width of a car. In my own experience, I get reduced passing clearance if I ride "close" to the LH lane edge. Things are much more congenial if I ride somewhere within the range of tire tracks. Personally, I like the "left center line of sweetness," but as with a lot in life, "it depends."

Very little of the mirror discussions I've seen address how mirrors are used for different purposes, nor exactly HOW you can reliably use a mirror for any safety purpose when considering traffic approaching from behind. For a movement you plan to the side - yes. From behind, not so much unless you are planning to jump on the brakes without warning.

MY VIEW (no pun intended)
A mirror can help in overall situation awareness. I'm going to get another mirror partly for this reason. What's more, it'll be a bar end mirror and NOT the one I already have that mounts on my helmet. A mirror makes a useful part of the "eyes moving" sequence of seeing what is all around (if that is any different than overall situation awareness) as long as it doesn't become an "end" in itself. A mirror can also help you prejudge a lane move. In this case, however, I'd never make a lane move without the "trust but verify" Ronald Reagan full head check. My kids were taught the same principle when motoring. NEVER change lanes without actually SEEING things are clear. In that regard, mirrors mainly help you know what to expect when the REAL look occurs.

"Trust, But Verify" Applies to Nuclear Weapons - AND Traffic (photo from Wikipedia)

All the above presumes you have normal vision or are farsighted. For those that are NEARSIGHTED, the mirror also helps them see what is happening back there and off to the side in conjunction with their eyeglasses. Otherwise, they are looking beyond the edges of their glasses.

If you were wondering, NO, I have NO side mirror on my 1967 Jaguar. I have no plans to add one either - unless I find some of those that'll clip onto one's window but can be removed when one drives on to the show field. Just sayin'

No Side Mirror on THIS Vehicle!


Principled Pragmatist said...

The main reason I use a mirror (glasses mounted Take-A-Look), by far, is to verify periodically (every few seconds) that the lane behind me remains unoccupied, and so I can continue to use the full lane, despite it being wide enough for safe side-by-side travel, or being adjacent to a bike lane. When I do observe traffic approaching from behind in such a situation (there is a bike lane or safe width to move aside into), I predictably look back over my shoulder, and maybe hand signal too, and then move aside, well before they reach me. Then, when I'm passed, I move back into my lane controlling position. Obviously, if traffic is too busy to make that practical (more moving left and right than is required when just moving left and right for intersections), I just stay in the secondary position, at least until I notice a long enough gap again in my mirror. In short, a mirror allows me to use the full lane much more often than when riding without a mirror. The advantages to this are well known: improved vantage to hazards ahead, and improved conspicuousness with respect to all potential traffic conflicts.

The second most important reason I use a mirror is when controlling lanes too narrow to be shared, to verify I've been noticed, and to know when to take a measure to elicit a response (changing lanes or slowing to my speed) out of someone approaching from behind. The vast majority slow or change lanes in plenty of time and space, but every once in a while a driver is a trance or something and needs a little nudge. The measures I take are usually just looking back over my shoulder or issuing the slow/stop arm signal, but occasionally I do a few zigs and zags. All these measures are amazingly effective at getting practically instant responses out of even the most brain-dead drivers.

In theory a mirror will tell me when the person behind is not reacting to even such efforts, and that I need to "bail", but I've never had that happen, and I don't expect it ever will. I believe taking earlier measures to get noticed is all that is ever required even with a very distracted driver.

In short, to evade a collision by swerving at the last instance is not even a reason that makes the list of why I use a mirror.

Steve A said...

Principled, speaking of your theory, I'm reminded that in theory, theory and practice are the same, but in practice they are not. I do not believe that a mirror can tell you that you need to "bail." I pray and expect neither of us will ever learn the truth in practice. However, I found that the notion of "bailing" was largely an illusion at and I had a LOT clearer view than any mirror. It gave the "danger is ahead" mantra a whole new meaning. Of course, I didn't wave or zig zag and that MIGHT have alerted the salmon an instant quicker. All I know is I do not want an encore to test the theory.

Principled Pragmatist said...

Anecdotally, I've heard several mirror users claim they avoided side swipes thanks to their mirror. But in all these cases they were riding far right where they were less conspicuous to the averted side swipers than they would be had they been out in the lane with a mirror.

Being conspicuously out in the lane greatly reduces the chances of being overlooked in the first place, and with a mirror you're able to distinguish, long before it's too late, those who have noticed you (the vast majority who change lanes or are slowing down) from those who have not (the occasional ones who continue barreling along as if you're not there).

When you're off to the side, even with a mirror, you can't tell them apart until it's practically too late to evade because their behavior is virtually indistinguishable. The motorist approaching a cyclist positioned out of his way typically maintains course and speed whether the cyclist is noticed or not. By the time he drifts at the last second, it's usually too late.

So, I still believe being out in the lane is a much more effective method than being out of the way and looking for drifters and side-swipers with a mirror. The conspicuous positioning enables you to grab their attention well before you move aside and side swiping even becomes a possibility.

I don't know how to measure how much safer the more conspicuous lane positioning that mirror use enables makes a cyclist, but I have no doubt that it makes an enormous positive difference in safety, simply by experiencing how it practically eliminates the close calls and other undesirable situations that occur much more frequently otherwise.

Khal said...

Nice discussion, Steve. Thank you.

I use a mirror on my commuter helmet, but not on my other helmets which do double duty for singletrack or weekend rides. I think they do add situational awareness if checked often and tactically (as I said on the LAB list, the speed differential between bikes and cars makes the dynamics of checking behind a little different). I tend to check the mirror to obtain information on traffic density as I am going into a situation when I am going to have to change lanes, change position in a lane, or get out of the bike lane to occupy a lane, such as when I am coming up on the roundabout near my house. The mirror doesn't take the place of a head swerve to look back at traffic, but it does encourage me to check early on and plan my strategy.

Given the rare nature of rear end collisions, I think one would have to be extremely lucky to be looking back just as the one bozo in >10^5 was reaching down to pick up his CD from the floor and suddenly getting squirrel on me. OTOH, a distracted motorist who is all over the road for some distance back might be noticed. Hence my sense that mirrors are oversold as part of the "fear of the rear" syndrome, but are still quite useful.

Ham said...

I use mirrors on cars all the time, to keep me aware of what's going on, providing part of the input that goes to make up the whole picture. On a bike I don't think that the image quality available is conducive to easy assimilation of data, and the field of view of just about any bike mirror I have seen has such weaknesses - inevitable with one, imo - that it could lead to a false impression of the surrounding traffic.

On a bile, I try to look behind before making any type of manoevre; the lifesaver. I can understand people wanting to use mirrors, but they're not for me.

Anonymous said...

As one of your near sighted readers, the mirror (take a look - helmet mounted), helps a lot with lane changes for the reasons you stated.
I still find myself reflexively doing a head check, but lack the clarity of vision (edge of the lens) to make them effective.

Edith Canon said...

Side mirros just get useful for me when I'm using the car but not with a bike. I have always feel secure when I'm riding my bike without having mirrors on them.

acline said...

I use a mirror. It's mounted on the handle bars of my main transportation bicycle. I do not use one on either my Brompton or my "recreation" bicycle -- although my rec bike has camera mounts all over it :-)

I think mirror use, like helmet use, is a decision for individual adults to make for themselves. I use one almost entirely because I ride in an urban core with three colleges, i.e. lots of texting and make-up applying students behind the wheels of deadly missiles.

I am not a slave to it (if I were, I'd have one on my other bicycles). And there is no substitute I've found for scanning -- if for no other reason than as a signal to motorists that I'm awake and watching.

RANTWICK said...

I swore by my mirror when I started, but now I don't use one. I can take 'em or leave 'em, I guess. I do like that you can measure how many cars might be stacking up behind you.

Chandra said...

Mirror is not a substitute for scanning, IMHO!
I like having one to keep an eye on the traffic behind me, many times in the lane that I am driving my bicycle in.

Very detailed and nice post! Loved reading it, at least 3x.

Peace :)

Eli Damon said...

Thanks for this analysis. At my deposition, the defense lawyer implied that mirrors were safety equipment. I have never heard of them classified that, and I have never heard any argument for their safety benefit. I was wondering if I had missed something.

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