Originally Posted by
Giro
The disproportion is, of course, that while overtaking crashes were only 9.8% of the 2,453 nonfatal crashes, these overtaking crashes accounted for 29.3% of the 41 fatalities in the 1990's data. Thus if you are involved in an overtaking crash, you are 29.3%/9.8% = about 3 times more likely to be killed than in an "average" crash. That probably reflects a combination of these crash types being direct rather than glancing (with higher acceleration of the cyclist's body), being literally run over, higher relative speeds, and possibly rural locations resulting in longer delays before paramedics get to the cyclist and the cyclist gets to a trauma center.
What you are considering is termed "exposure" in the risk literature, which allows calculation of absolute risks and comparison of risks (e.g being a motorist vs a cyclist). Unlike with motor vehicles, good numbers for exposure of cyclists are unfortunately lacking. There just aren't precise numbers for miles cycled per year per cyclist or hours per year or passing events or intersection events, rural miles vs urban miles, etc. This makes it difficult to compare countries or interventions (helmets, bike lanes, vehicular cycling, etc.), resulting in endless arguments on interventions or the risk of driving vs. cycling.
It also means cyclists do not have really hard data on what risks to watch out for under what cycling environments. The best we can do is make judgments informed by compilations of crash types, personal observations while cycling, books such as Hurst's, etc. Then you can be aware of what to watch out for in what cycling environments, which may change moment to moment. In a rural environment with few intersections, narrower roads, and motor vehicles overtaking at high speeds I try to be aware to the rear (e.g. is that overtaking motor vehicle showing any sign of moving over, slowing down, towing a wide trailer, ...), have good rear conspicuity (lane positioning, high visibility clothing, bright daytime tail lights etc.), think about about where I would bail out on the shoulder, etc. A midblock grade level crossing on a MUP brings an entirely different set of concerns (including abandoning the MUP if such crossings are frequent).
Yes, all of the above. I'm talking about exposure and the misleading presentation of relative-risk versus absolute-risk (e.g. your "three times more likely" example above). I may be 1000 times more likely to die when being hit by an asteroid than when hit by an automobile, but presenting that as "you are disproportionately more likely to die when hit by an asteroid than a car" does not mean I should start looking for an asteroid deflection shield.
And I think we can make a good guesstimate that we are overtaken far more often than we pass cars at intersections.
In any event the other thing that your data (incomplete though it is) show are:
1. As a percentage of total incidents (summing overtaking + other, rounding up)
1977
Fatal overtaking: 7
Fatal otehr: 11
1990
Fatal overtaking: 0.5
Fatal other: 1
e.g. as is indicated by other data things have gotten a lot better since the 70s and there's no obviously massive threat from overtaking incidents.