salcedo

I know it feels awful to have a truck, or even a small car, passing just inches away at high speed. And common sense suggests that a close passes increase the chance of an accident. But is that increase significant or is it just perceived risk?

The most common types of bike accidents involving a car appear to be: right hooks, left crosses, and dooring.

Mirror and tire clippings do happen. But I suspect that they are often the result of a driver being distracted and not seeing the cyclist, or a punishment pass from a driver suffering road rage. If a driver notices the cyclist and decides to pass him closely but paying attention, how big is the probability of an accident occurring?

If anyone has a link to a good-quality study or some data I would love to see that

Cyclist0108

I've often wondered the same thing. The primary dangers I would think are (a) startling the cyclist, which could lead to a collision due to a panic reaction, (b) the less room there is, the less margin for error, such as the cyclist swerving slightly to miss an acorn or pebble, and gets hit, or (c) slipstream, which would be worse with a high-speed truck, or (d) the driver misjudges the distance when attempting a close-pass (worse when incapacitated), or swerves to avoid an acorn, squirrel, on-coming car, suffers a wasp sting, etc, and the anticipated close-pass becomes a direct hit.

That is enough to make me uptight.

FBinNY 

I agree that close passes increase the risk of miscalculation and collision. Also the wind and and fear induced swerve, and cause the bike to crash even if untouched.

However, that's about statistical risk. Once a driver has passed you and you haven't crashed, it's not logical to call that particular pass unsafe since nothing happened.

I lived and ridden in NYC and the metro area for over 50 years and have experienced my share of close passes. But other than an under the breath "dammit", haven't seen fit to fuss over them. Riding in dense city traffic you quickly learn that close only counts in horseshoes.

This doesn't mean I like close passes, nor that I don't wish drivers move over more, but over the years I've come to the conclusion that passing speed is more important to me.

Pass going 5-10mph faster than I am, and be as close as you can judge. After all, I'll pass cars with inches to spare. OTOH - fly by at 45mph and I really want some room. When friends ask me about passing bikes, I give them my personal guideline: 1 foot clearance for every 10mph of their speed.

mr_bill

Once you've survived a particular round of Russian Roulette, it's not logical to call that particular round unsafe since nothing happened. (And in close passes, the driver is pointing their weapon at someone else's head.)

You want to rethink your "logic?"

-mr. bill

FBinNY 

No, I'm comfortable with what I wrote. Just read the whole post.

But, of course, you or anyone else is free to disagree.

mr_bill

Logically, nothing at all unsafe happened on the Deep Horizon - until it blew up.

But of course, someone might disagree.

-mr. bill

carl7

What scares me most about close passes is the inability or poor judgment of some drivers. Some of those close passes you experience may not have been intended to be that close but because of poor judgment.....

Ninety5rpm

Passing cyclists closely is a dangerous habit. Sure 10 times or 100 times or 1000 times maybe nothing will happen, but without leaving that margin for error, sooner or later the situation might need it and it won't be there. That's what makes it unsafe.

wphamilton

Risk vs "statistical risk" is a distinction without meaning. "Statistical" is just a way of describing risk, not a different kind of risk.

I have wondered why people tend to erroneously believe that an observed outcome demonstrates that there was no risk, and something just now occurred to me. Triggered by that phrase "just statistical risk" it strikes me that people are thinking of risk as something inherent in a given situation. If everything follows physical laws (forget quantum mechanics) the outcome is always determined by the initial conditions. If nothing bad happens, then they reason that risk was zero. If something does happen, the risk was 100%. I think, when you get to the bottom of it, that's how people are seeing "risk" when they reason this way. Am I wrong?

That's not really what physical risk is though. It's not a physical property, not an inherent system state. Risk is a description which depends on what you don't know about the system. If you know every physical characteristic of a quarter, and of the surface it falls on, and the precise magnitude, position and direction of the force you use to flip it, a precise enough calculation would tell you whether it will land heads up or tails. There would be no risk in betting heads if you know it will land heads. But only because we don't know those things, we have a 50% risk of a bad outcome. We don't know, because the situation we describe is "flip a coin" and that includes ALL the variations of variables that we don't know.

The risk from a close pass is like that. Exactly like that. The risk of a "close pass" was no less just because the last one missed us. The risk of the next close pass is unaffected by the result of the last one. The "risk" that we're describing is the chance of *any* close pass causing an accident. Describing it more discretely does change the risk, but the outcome of one does not.

noisebeam

Just get a mirror. No more concerns about close passes.

dabac

Well, the POSSIBLE consequences of a close pass CAN be fatal.
No doubt about that.
Getting nudged off the road can mean crashing into something rather unforgiving.
Losing one’s balance can mean wobbling out into the road, to be run over or rammed by a car.
How LIKELY either rider or driver is to swerwe at the most unfortunate moment, I have no firm opinion.

WNCGoater

I think as in so many threads, we've ended up quickly discussing two subjects.
The title of the OP is, "How dangerous are close passes really?"
Well that question has already defined the outcome, as in past tense, it was a "close pass", and so by definition, there was no contact. As in, " Holy *%&$ that was a close pass."
In that context a close pass poses no danger.

Passing closely, or intent to make a close pass, or habitually passing closely, is exceedingly dangerous in my opinion, and for all the reasons outlined in previous responses above. Once past, it is now a "close pass" and there is no danger involved.
And so a close pass has no danger involved. Passing closely is indeed dangerous.

Or so goes the logic in these threads.

To the OP. I try to live by, "any pass without contact is good", rather than getting riled by those jerks that are trying to make a statement. I don't enjoy "close passes" and of course, those passes put us in a short state of heightened danger because of a lack of any margin for error. I use a rear view and watch every car passing, making sure they are leaving enough room coming around me, and I'm always ready to hit the ditch for any car that is apparently distracted and unaware I'm there.

I can't stand all the statistical mumbo-jumbo BS that always springs up in these threads but I doubt there is any statistical data that would indicate anything concerning close passes as it is a "pass". If it becomes a non-pass, and without witnesses, I'm sure it is likely just recorded as a car/bike collision, statistically speaking.

indyfabz

How did you come to that conclusion?

noisebeam

Over decade and 100k+ miles of riding in rush hour traffic daily. ~90% of that with a mirror.

Dave Cutter

+1

Emotional reaction... fear of traffic is common.... understandability because cars and trucks can cause serious ouchies. But emotional reaction.... in no way effects actual risk. Even Tiny hybrid cars can do fatal damage. Although loud trucks that carry with them a strong wind/draft seem to produce the greatest concern.

wphamilton

Statistics do indeed exist, such as the FARS data. Estimated that at least 33% of bicycle fatalities in traffic involve a car overtaking a bicycle. i.e, a close pass by definition. That's not as helpful as it may seem though, since there are many thousands of times as many serious bicycle injuries as there are fatalities, and a major factor in fatalities may not be as big factor in other injuries.

It wouldn't be impossible to determine if risk correlated with how close a pass is. Observe enough interactions, count the accidents. In spite of the common-sense reasoning that more closer passes will cause more injuries, I strongly suspect that from 1-3 feet there wouldn't be much difference. Not as much room for error, sure, but inside of 3 feet the driver error might be likely to hit the cyclist regardless. I think that's probably the case. If I'm right, a 3-ft close pass is (almost) as dangerous as a 1-ft pass.

I-Like-To-Bike

You are using the term "risk" as an equivalent in meaning or measurement to the term "probability"; it does not mean the same thing.

Probability is a component of measuring risk; credible estimation of bicycling risk also requires evaluation of the outcome from a negative event such as a collision/fall (i.e. likely severity of injuries that could be expected if the negative event occurs.)

You are correct that the probability of a close pass leading to a negative event is unaffected by the result of the last or next close pass. Of course the same could be said for the coin flipping exercise.

Not so for the probability of a negative event from playing Russian Roulette if the revolver barrel is not spun around before the next trigger pull. Otherwise each trigger pull puts the "player" at increased risk because the probability of the negative event (a bullet in the head) increases though the likely severity remains constant.

The bottom line is that bicycling risk from various bicycling scenarios is not evaluated properly by estimating/measuring/recording only the probability of negative events occurring, though many sloppy, careless or biased so-called "studies" do just that and ignore likely severity of injuries incurred from such negative events.

indyfabz

But your assertion reads as if a close pass is impossible as long as one is wearing a mirror. What if one has a mirror but has no way to avoid a close pass? For example, ever descended a mountain pass with no shoulder and nothing but guardrail on your right? You can have 60 mirrors and still have to be concerned about that logging truck or RV passing to closely.

1989Pre 

Just do what you do and don't worry about it. Hold your line and don't panic.

Dave Cutter

At a Thanksgiving dinner I heard a person say:.... They had increased their "odds" of winning the lottery.... because they were now buying 50 chances a week.

I said you know the odds haven't actually changed... right. They replied:.... Yeah but my chances are much greater, and that's almost the same thing.

I smiled.

Ninety5rpm

A mirror mitigates close pass issues in at least these ways:

• The mirror enables one to fine-tune positioning to effectively inhibit the close passing in the first place.
• You see it coming, so you can see the straight/safe close-but-not-too-close trajectory, and know you're not threatened. It doesn't startle you into swerving.
• It gives you time to adjust, if deemed necessary.
• By simply staying apprised of what's going on behind you, it just ceases to be a concern.

wphamilton

I'm not, but the distinction might be subtle. My description is transitive from probability through to "risk", because risk is simply the product of the probability and a valuation of the outcome (summed over all potential outcomes).

Ninety5rpm

I don't want to be hit by a car, period. Choosing where/how to ride based on the likely severity of the more likely bike-car crash type making one choice rather than another sounds like pointless hair splitting to me, even if sufficient data existed to make such choices.

Your thinking is exactly what leads cyclists to prefer risking a dooring, right hook, left cross or pullout (all of which known to be deadly) by riding near the edge rather than using the full lane because the likely severity of being hit from behind is assumed to be so much higher that the likelihood of such crash occurring, compared to the likelihoods of all the crossing conflicts crashes occurring while edge riding, is hardly considered, if at all.

The likely severity of any collision with a car is unacceptably high. So I'm much more concerned with reducing my risk of any kind of crash with a car than with reducing primarily only certain types, especially at the risk of significantly increasing the probability of increasing other types of crashes just because the likely severity might be a bit less.

noisebeam

Exactly. Key to bullet 3 is that one always leaves clear space move further right.
When using a mirror I have never been surprised by someone passing. I have always had space to my right to move into if I felt I wanted more clearance.
When I hear a cyclist complain about close passes I know they either don't use a mirror or they do use one but still ride in fear hugging the curb or road edge.

FBinNY 

However, they were right. If the odds of winning with a single ticket is one in a million, the odds of winning with 50 tickets (with different numbers) is 50 in a million. So the odds of winning are improved. OTOH, the odds measured in dollars hopefully won vs. dollars bet are the same.