Linky fixed above.

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http://www.youtube.com/hyperpack

I explained at some length in a keynote speech a few years ago how we wound up with NHTSA effectively unable to regulate car lights in the USA at more than a basic, lax level.
This right here is the nub of the problem: as we age, we need more light to see any given thing, and at the same time we grow more sensitive to glare. And "Hey, the headlamps on this model won't piss off other drivers as much as headlamps on other cars" is not an effective sales pitch.

It is effectively impossible to point to a particular spot on the seeing light/glare light tradeoff and go "Right there! There's the perfect balance!". For decades, the European regulations (which are now the UN regs, which most of the world uses outside the North American regulatory island) have placed a much higher priority than the US regs on glare control. The EU/UN low beam specification allows less glare toward oncoming drivers (though it allows much more upward stray light --> backdazzle in bad weather) than the US specification. Periodic vehicle inspections are a fact of life in most of the rest of the world, during which headlamp aim is checked, and aim is routinely set lower than in the US/Canada. More vehicles in the rest of the world have automatic headlamp levelling systems to keep the beams down despite vehicle load. Etc.

But glare compliants are sharply rising not just on the American regulatory island, but even in countries with much more stringent glare regulations. That points at unregulated factors common around the world: smaller, brighter, bluer.
That's another problem. The same stylists and marketers who demand tiny, slim headlamps demand tiny rear lights, too, and what the stylists and marketers want, they get—no matter what the engineers and scientists say. The US/Canada regs require 50 square centimetres (=7.75 square inches) of lit area for each rear turn signal and each brake light. That rule was enacted specifically to avoid high luminance that would cause glare when you're stuck in traffic staring at the lights at close range. No such rule applies elsewhere in the world, but the intensity limits are lower for rear light functions, too, which helps with the glare. Here on the we're-right-and-the-stupid-rest-of-the-world-is-wrong American regulatory island, automakers started bending that rule awhile back: a tiny little ultra-bright brake light, but they'd also turn on the bigger taillight whenever the driver stepped on the brake, and claim the total lit area of [brake + tail] as their 50 cm2. That is a bad-faith move—it's not what the rule intended—but NHTSA never spanked any of them, so now they don't even bother with the taillight trick any more. Tesla Model 3 (maybe 7 cm2 if we're generous), Toyota RAV4 and Lexus NX (maybe 10 cm2, maybe), and a whole lot more. NHTSA stares at the sky and goes "Huh, looks like it might rain".

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

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.

Old style US headlights "sealed beam" have been mystery for me. We have here in europe asymmetric low beams with accurate limit how much light goes to the sky. High beams are mostly for long distance and they did the job well. Every sealed beam I've seen was just a short lighted area in front of the car and the high beam above it. And not so powerful for anything. We got H4 bulbs 50 years ago which made the lights even better.

I have changed at least hundred imported US car headlights to local versions by replacing the lamps, bulbs and mixing the socket pins (they have same socket but different pin out.

In the past we had possibility to double or even triple the headlights which was nice. Then only the high beams were free to get doubled.

...and also now we have those "stupid" ledbars with no accurate profile of light beams....

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1966 Dart. 170 cu.in. 200 rwhp.

I agree completely. For the sake of profit, American car design has lagged behind the rest of the civilized world for decades. American isolationist thinking that just because something is American, it must be superior, prevented improvement of things like automotive headlamp systems for decades. The old sealed beam headlamps should have been retired in the 1960s but US automakers refused to change.

That said, I am not a fan of the look or performance of modern LED headlights. I will stick with my old H4 conversion lamps as long as possible.

Personally I believe that the only reason that american companies have started putting actual light emitting objects on the front of cars is because of IIHS starting to test new models around 10-12 years ago. A bunch of OEMs got slammed with "poor" ratings on many of their products due to piss poor factory headlamps.

I remember a specific case were the base model of a popular midsize with halogen projetors got rated "good" but the top trim level car with LED projectors got a "poor."

The OEMs will do anything to get their products a 5 star safety rating and having a poor for headlamps makes them scared.

I'm not saying that modern cars have "better" headlamps for oncoming traffic, but the cutoffs in recent years are much sharper with more intense patterns. I see new headlamps from a variety of cars shining on the wall as I pull them in most days, so not the most scientific testing obviously.....

edit... I looked at the IIHS website and the first model year that headlamps are listed in the rating is 2016.

The IIHS headlight ratings are the best out there in the North American market, and they give quite a lot of information if they are interpreted correctly. To take them at face value is to stand a good chance of reaching a wrong conclusion. The trouble is on IIHS' end; they're claiming the ratings indicate how good or bad the headlamps are on a given year-make-model of car. In fact, the ratings indicate how good or bad the headlight performance is on the specific, individual car they tested. The reason for this is that they don't adjust/correct the lamp aim before doing their testing. Their rationale for not doing so is sturdy—in North America it's been many years since headlamp aim was cared about, generally, even though it is the primary main № 1 factor affecting how well you can see and how much glare you're throwing around.

Fact is, though, it's more important now than ever before; today's headlamps are much more sensitive to misaim than older types. So the IIHS tests are doing a good thing—creating an incentive for automakers to get more careful about new-car lamp aim, which they're doing (at least until whatever model gets its IIHS ranking)—but IIHS aren't really describing what they're doing.

Here, in a nutshell, is how to usefully interpret the IIHS ratings:

Headlamps that give long seeing distance in most or all directions, but create glare: probably aimed too high.

Headlamps that give short seeing distance and no glare: probably aimed too low

Headlamps that give short seeing distance and create glare: probably bad headlamps.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.