Here is this 25 minutes long video on YouTube titled “The Surprising Truth About BRIGHTER HEADLIGHTS Nobody Tells You” https://www.youtube.com/watch?v=9-jffAiBR7Y, fairly recent, posted on Dec 21, 2024.
The video and its 1,349 comments are very useful.

Some main points are:
“all the vehicles that dazzle me are typically less than five years old, so the dazzling issue doesn’t come from people with older cars fitting illegal LED bulbs, rather from the somehow legal factory fitted units in modern vehicles”

“How many vehicles do you see driving around at night with no lights on, because the running lights are so bright they don`t even notice…?”

“Here’s the dangerous thing about very bright headlights. The contrast ratio between the dark area outside of the headlights is perceptually darker with much brighter lit areas. These areas are much more defined with new lamps as well. With the brighter lights our iris closed down and the contrast ratio means especially in poorly lit or unlit road areas means if an animal child or object is in the unlit zone you will not see it until it moves into the lit zone and depending on your beam spread and contrast ratio and speed you are actually much more likely to hit that object.”

“With white LED light I feel like I can’t see beyond the dipped beam. The contrast between the bright white light and the darkness beyond becomes to large. With the more natural coloured light of the halogen bulbs, I can still kinda see beyond the light, look more into the distance.”

“This whole issue could be much better here in the USA if our Department Of Transportation (DOT) would abandoned their ridiculous rules that date back to the 1960s on automotive headlights. Technology exists like Audi’s Adaptive Lighting that will progressively prevent blinding oncoming drivers using an adaptive beam. But our DOT has prohibited that technology for many, many years.”

“not only are modern LEDs more intense but there is no warm up time, so when a car coming towards you flashes you , like you just pulled in to let them past, instant full power lasering your eyeballs, on a halogen bulb you get a few milliseconds to blink, or at least for your eye to adjust.”

“If councils used cats eye’s and painted the sides of the roads it would help, but they seem to get rid of them when any resurfacing takes place on A roads”

“LED madness, its not just the headlights its brake lights as well. Most drivers seem to sit in a que with their foot on the brakes, blinding the driver behind. Even the LED traffic lights are too bright!”

“Most people don’t care that these bulbs are illegal, and they don’t care about having better lighting either, they just think it looks “cool”…”

“Well, I didn’t know some bulbs are not E-marked. It explains a lot!”

“My motorcycle lights are pathetic! Clearly we’re not supposed to ride at night. I’ll need to get spots but first I need to get crash bars to mount them. It’s a mission to get proper lights on a motorcycle,”

“I recall a rider in the 90s saying his 125cc actually slowed down when he turned the headlight on. The engine was that weak, and it was lower-wattage than car headlights. He had a bicycle light taped to the front as it was better! lol These days, LEDs would definitely be the way to go on a bike like that.”

“Small LED lamps including their own tiny projector lenses for low-beam cut-off seem particularly interesting for older reflectors,”

“this article in The Times 2/4/24, “Official figures shared by the RAC show that since 2013, an average of 280 collisions occur on Britain’s roads every year in which headlight dazzle was a contributory factor. Of these, six a year involve someone being killed.””

“the excessive reflectivity of road signs. Most of my night blindness comes from my own headlights shining back at me when approaching a road sign. Modern signs are just too reflective, to the point where, when shining on them, they wash out, rather than stand out and let you read the text or images.”

“some newer cars seem to be extra bright on the ground (technically not blinding you) but if its raining or at least wet on the ground you get blinded by the reflection”

“It’s cyclists with super bright LED lights that I find most blinding at night. Usually pointed directly at the oncoming car driver’s eyes!”

There are other gems in the comments as well, please read and be enlightened. You can also watch the video if you like.

For many car brands, bulbs are a part of the circuit.

For some cars, they don’t take the sign to cancel the cruise control from the brake switch. Rather, they monitor when the brake bulbs come on, the current and resistance of the circuit increases. If you replace those 7443 dual filament (or even 7440 single filament CHMSL) with LED bulbs, the current will 4-5 times less, either the cruise control will stop functioning, or in a worst case scenario it will refuse to disengage automatically when you press the pedal. You’ll have to use the switch on the steering wheel to cancel the cruise, which means you’ll lose crucial few seconds before the cars begins decelerating.

For some cars, the dashboard backlights are also part of the circuit which shows low-fuel light, etc.

Changing the W5W/WY5W or W21W/WY21W bulbs with LED bulbs can cause hyper-flash.

Not to mention that some LEDs flicker, so even when selecting LED bulbs for benign purposes like number plate lights or parking bulbs, you have to be careful.

Some projectors also allow quite a little bit of light above the cutoff line. That light is fairly mild, quite non-dazzling but is able to light up the e.g. reflective road signs and road markings very good. You have to get used to it as the area below the cutoff is much brighter compared to a conventional headlighting setup.

All in all projectors are worthwhile upgrade and all manufacturers must offer them.

After having a long drive on the desolate Batinah Expressway this last summer, here are my observations:

Low beam: The cutoff of a projection lamp is too sharp, with a nearby area floodlit while there is complete black-hole level darkness beyond the cutoff. In contrast, the halogen reflector headlights have a slight leakage of light above the cutoff, while slightly annoying for the drivers ahead/oncoming, it makes the white lane markings a little more apparent beyond the natural range of the low beam headlights.

High beam: this particular specimen was an upgrade model, with projector high beams (of course without a cutoff). The low beam lights were separate and the high beam lights were separate. The high beams were particularly effective with the added benefit that they cause less glare for oncoming drivers despite producing more light than the standard halogen high beams. This may be because of the small size of the projector lens itself.

Later on I drove above 800 km single highway without any shoulder and with dimming lane markings, a few hundred kilometers in the evening after dusk when the sun had set and the moon hadn’t dawned yet. I found the result of the halogen reflectors somewhat satisfying because of the leakage above the cutoff, it was possible to identify any road markings and road defects beyond the hotspot and beyond the cutoff. Because of the dim light, seeing in the distance in the backwash of a car that’s approaching from a few kilometers beyond, from behind a sand dune or behind the next turn in the mountain roads was possible due to eyes already adjusted to the dark.

All in all I’m torn between halogen reflector vs LED projector now with no decisive answer.

Not all projectors are equal.
It depends upon whether the projector lens is for halogen, HID or LED bulb.
It also depends upon whether the correct technology bulb is being used in compliance with the lens type. An HID bulb in a halogen projector will look and perform horribly.
It also depends upon the aberrations in the lens.
It also depends upon whether the lens is clear or clouded. (Some projection lenses are cloudy by design, appear foggy, it is not because of age or moisture).

Many people take a good OEM headlight and retrofit the projection lens and bulb from it into their stock halogen reflector housing. Aftermarket full0size projectors or mini-projectors are also available.

More info here: https://blog.theretrofitsource.com/headlight-tech-hid-projectors

Apparently, small-lens (miniature lens) projector bulbs do not perform as good as full-size projectors or mini-projectors.

Here’s 2 videos discussing that:

https://www.youtube.com/watch?v=vDi-fIp0jkw 18 minutes
Jan 24, 2022
Installing LED Projector headlights in my 2002 TundraJDM Driveway

https://www.youtube.com/watch?v=fSn17LT_Zog 12 minutes
Feb 28, 2024
The TRUTH About Headlight Upgrades | Colight Mini Projector vs Morimoto Micro D2S208Tyler

Keep notice that this is not a projector lens retrofit, this is just a headlight bulb replacement which comes with its own miniature projection lens integrated into the bulb along with the mandatory cutoff. Bonus is that it doesn’t have any moving parts (high beam shutter).

There is a slight alteration: if your car’s headlights came fitted with the small bucket reflector that covers the bulb, you’ll have to remove it. Not necessary to blacken the bowl reflector at the back of the light housing.

The dome light (reading lights) is one of the usual culprit! You can begin your tungsten-to-LED retrofit journey from the dome light. It is the easiest to replace in most makes and the increased amount of light is better too.

Changing the W5W parking light bulbs to LED, dashboard backlighting bulbs to LED and the tail-light bulbs (also if you’ve tail+brake combination bulbs) to LED has another benefit! If you forget to turn off the parking lights and leave them on by mistake overnight, the current draw on the battery will be very less! and thus, there is far more chance that the battery won’t be dead in the morning and the engine will turn over when you crank the starter!

I learnt it the hard way, but you don’t.

Sounding like an AI narrator, in only 18 minutes, this video gives us a concise comprehensive history as well as the current state of the art of headlighting. Must watch!

See the adaptive LED matrix headlight in this video:

https://www.pakwheels.com/blog/mercedes-eqe-350-is-smarter-than-its-counter-evs-owner-review/
Mercedes EQE 350+ is Smarter Than Its Counter-EVs – Owner ReviewJul 08, 2024

The direct link to the exact time in the relevant video is this: https://youtu.be/Zo6JXxqK5RA?t=611

I wish all the cars, trucks, buses, rickshaws, motorcycles and tractor trolleys came with this important safety feature – at an affordable cost of course. Let’s pray for the best.