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Hereis an Eye Doctor's take on the issue.
I was more or less onside with most of what he said up until that last thing, the suggestion to brighten the dashboard lights. That's the opposite of a good idea; it's much(!) safer, in terms of your ability to see what you need to not hit, to turn the dashlights
down as low as they can be while still letting you read the dashboard at a quick glance.
I think the main fault with this vid is that the doctor ignores the difference between the two kinds of glare, and just talks about "glare" as if it's one thing. It is not.
Discomfort glare is exactly what it sounds like: it's uncomfortable or even painful.
Disability glare, too, is just what it sounds like: it degrades our ability to see. The two kinds of glare don't work the way common sense or our everyday experience might suggest. It's tempting to think it's a simple climbing-numbers scale, where below a certain point it's "just" discomfort glare, and once it reaches some threshold amount, then it goes beyond discomfort and into disability glare.
But it doesn't work that way at all. In fact, there's always some disability glare; even the smallest source of light in our visual field degrades our ability to see by some degree. Massively overlit gas stations and jumbotron billboards are obvious offenders here, but a driver's own dashboard lights are a significant contributor, too. That's got much worse recently as dashboard illumination has changed from a few small bulbs to big, bright touchscreens and displays casting so much light that at night you can see drivers' faces lit up by their dashboards.
Another counterintuitive, crucial thing to understand here is that it is possible—and rather common—for there to be significant glare-induced degradation of our ability to see (disability glare) with little or no
discomfort, and for there to be significant glare-induced pain and suffering (discomfort glare) with little or no diminution of visual performance. When we go "GAHH, get those lights out my eyes, I CAN'T SEE, I'M BEING
BLINDED!", that's certainly what it feels like, and it might be true to one or another degree, but it also might not be. In fact the one doesn't
follow from the other.
This has been studied extensively, and despite many years of dilligent looking for a direct causal link between discomfort glare and crashes, none has been found. That doesn't mean it doesn't exist; it very well might, but it is much harder to make that connection than to make the one between disability glare and crashes.
Disability glare --> driver's visual acuity diminished by some objective, quantifiable amount --> driver didn't see the pedestrian (it's overwhelmingly a pedestrian) --> crash. Easy, and measurable at every step.
Discomfort glare --> ??? --> ??? --> crash. Those question marks stand in for a big bunch of complexity and murkiness. For one thing, it's probably not a tidy, simple matter of a single high-glare vehicle
causing a single other driver to crash. It's probably more likely a steady, constant stream of glare gradually, progressively fatigues and distracts a driver until eventually something bad happens. Or it could be even less direct than that; perhaps a steady, constant stream of glare creates kind of a "hostile work environment" for the driver, grinding at the driver's nerves and patience such that they unconsciously drive more aggressively or carelessly. It's very difficult to check for such a cause/effect relationship, so if it does exist, we don't (yet?) know.
Another complication: the human visual system is a lousy judge of itself. "I know what I can see!" seems reasonable, but it doesn't square up with reality because we humans are just not well equipped to
accurately evaluate how well or poorly we can see, or how well a headlamp works. Our subjective impressions tend to be very far out of line with objective, real measurements of how well we can('t) see; or
how much (or little) any given level of glare is affecting our ability to see.
So yeah, as I was saying: complex!
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一期一会
Too many people who were born on third base actually believe they've hit a triple.
