There is only so much light you are legally allowed to emit to the roadway. LED lighting features a really nice white brilliance, but they are not actually shining further down the road (that would be illegal in terms of aim). 20 year old Halogens light the way just fine when they are aimed properly, with good bulbs, and clean lenses. Same with HID systems. The only time there is an improvement is with the high beam. Then HID can really help over halogens. A halogen high beam is awful.
In my opinion, and that of some optometrist friends of mine...I believe that HID/LED lamps reduce your ability to see farther down the road because they reflect too much light back into your eyes from the road surface. This makes your pupil contract and not be able to absorb the light from farther ahead, so see it reflecting off an object/person far away. It's the same problem when your gauge brightness is turned all the way up.
Also, the biggest drawback to LED front lamps is lack of heat. To get snow/ice to melt off the front of the lamp in a snow storm you actually need the heat of the lamp. A supplementary heater might even be required. At least in the winter the LED lamp would need to consume the same amount of power as an HID, when you include a heating system.
A halogen lamp costs the OEM manufacturer something like $20-$35 per side, per car... $50 versus say $200 per car for the LEDs is a lot of money to pay just to say you have LED lamps on an economy car. This is why we don't see more economy cars with LED headlights, although even the new Toyota Corolla has LED headlights. The COROLLA! Would you ever think the day would come when a COROLLA features newer/better technology than a Mercedes-Benz?
What works best for the manufacturers is offering LED headlights 'available' as an option, and then charging about $500 for them (or more in the case of a Mercedes-Benz options sheet). OEM pays the $200, and they make at least $300 off the customer in pure profit. Customer is happy because his car has HID/LED lamps.
Now I am not a scientist but I believe the reason that HID/LED does not light up as well as halogen in certain situations is due to the emitted spectrum
Most halogens are like 3000-4000k which does a good job at lighting up rain and fog as well as objects that are black (the ground) without reflecting too much light.
HIDs are usually 4000-4500k from the factory. Tiny bit more white which is more reflective off surfaces.
But HIDs throw out a ton more LUMENS compared to Halogens which make up for it.
I think as long as you stay under 45000k with HIDs it should help in lighting up the road. Of course having proper aim is essential.
Halogen reflectors (at least most of them) dont really reflect the light very well. Its spread out towards you. Where as HID projectors usually aim the light very sharply.
I dont know too much about LEDs and how much lumens they output or what the spectrum of light is but I would assume manufacturers do testing before they put them out.
I think at the very least the GLA and CLA should have came standard with Xenon/HID headlights.
Fine LEDs are expensive sure. I'll disregard that the new Corolla and the Honda Accord can come with LED headlights.
But at least give us xenons please.
Here is an example of Xenons that are very white and reflect some light back at the driver (not a good thing)
You can see the halogens are more comfortable to view but do not light up as far. The xenons light up farther but are tiring on your eyes.
But I believe those lights are around 5000k in the Xenon photo.
They even make HID/Xenon bulbs in 3000k if you really wanted.
Here is a more even comparison. Both halogen and xenon are around 4300k
The xenon lights up farther and wider (thanks to the superior reflectors in xenons)
Common halogen reflector lightbeam
Common xenon lightbeam
In just a few words, there are the pros and cons of halogen headlamps:
ADVANTAGES:
- longer life
- different dimensions
- very efficient
- bright illumination
DISADVANTAGES:
- energy wasting
- extra care required
pros and cons of xenon lights:
ADVANTAGES:
- longer lifetime than halogen lights
- more efficient than halogen as they use less power
- better visibility for the driver
DISADVANTAGES:
- too much glare and thus, potential problems for the incoming traffic
- very high costs
- possible harmful materials could be used
LED headlights:
ADVANTAGES:
- small size, allow great manipulation for various shapes
- very low energy consumption
DISADVANTAGES:
- high production costs
- low amount of generated power
- high temperature created around adjacent assemblies
Hope that helps everyone....