LED headlights

[nealeb]

Right, then, guys. After conversations with both Audi Customer Services and my local Audi dealer, both of whom tried very hard to be helpful but failed (mainly because neither of these worthy organisations have actually had any real hands-on experience of LED headlights), I thought that it was time for a bit of science. So, as founder and sole member of the Sad Old Audi-Owning Geek Club (South Hampshire branch), I set up a controlled experiment this evening, once it was dark enough to see beam patterns on the road. I asked my wife (who wishes me to point out that this was really pretty wonderful and understanding of her) to take her A3 around a local circuit of unlighted country roads, all pretty straight although with some up-and-down sections while I followed.

I was looking to understand three features of the headlights. These were "adaptive lights" and "high-beam assist" (also called main beam assist in some places) which are specifically mentioned in the brochure, and "range assist" which is only mentioned in the driver's manual. Here is what I found, and what I believe each of these terms actually means in practice. Assume for all this that the light switch is set to "Auto", both automatic light settings in the MMI are set to "On", and the dip switch has been pushed away from you once and the auto lights symbol is showing up in the DIS.

First of all, high-beam assist. This is the easiest one to see. On a dark road with no-one else around, no street lights, etc, main beam is on - and it is very, very, bright. Lots of light everywhere. As soon as another car comes into sight, whether someone you are following or an oncoming car, the car switches to dip. It's like turning off the sun. Very sharp cutoff to the top of the dip beam, and complete darkness beyond. So, no dazzle for other road users. Once the other vehicle is out of sight, back comes main beam. You also see this when following a car on an up-and-down road as the car in front disappears and reappears. The system works very well, but the contrast between main on and off is a bit off-putting at first - "Where's the world in front gone?"

Then comes the more subtle effect of range assist (I'll get back to the adaptive lights in a moment). If you are following another car, you will be on dip, as above. So I set myself a reasonable distance from the car in front and noted that the top of dip beam was somewhere between number plate and bumper (the beam cutoff is really that sharp). As I closed the gap or dropped back, the top of dip beam stayed just about between number plate and bumper. In other words, the dip beam rose and fell to compensate for distance, and my wife's comment afterwards was that at no time was she dazzled by my bright lights behind, however close I came. The system got a little confused going over the summit of some of the hilly bits because it couldn't react fast enough, but even then it didn't seem to give the car in front a particular problem. As soon as it saw an oncoming car, as far as I could tell it dipped as far as it could. The adaptive bit might have kicked in as well (see below) but given that the bit of the beam that would have dipped most was by then illuminated by the other car's dip beam, it was difficult to tell. One reason why I had found it difficult to see the range assist working previously is that it pretty much only works when following another car. Oncoming cars trip high-beam assist which is almost literally a lot more bang-bang in operation.

Then we come to the adaptive lights. The previous two features are pretty much the same for the "adaptive bi-xenon" and LED headlights except that the xenons vary continuously between main and dip so the on/off main beam effect is not quite so severe. Adaptive lights differ between the two. Adaptive xenons include the range assist feature (as for the LED) but they also swivel with the steering and possibly based on input from the nav system so that they "look round corners". Works quite well, too (I've test driven a car with them), but this is not needed for LED lights which put out lots of light, everywhere. Did I mention how bright the LEDs are? Anyone who thinks that LEDs are restricted to indicator lights on electronic equipment really should see these. In addition, the xenon lights go up and down together as a pair, as far as I could tell, and apart from the "range change" the beam shape stays constant. What I found difficult to see although the Audi advertising and other literature claims happens is that the two LED headlights can adjust independently so that one can dip to avoid dazzling while the other stays up, for example. Audi also claim that the beam shape can vary according to whether you are in town, country, motorway or whatever. I think that I saw some changes in the shape of the beam on the road but to be honest it's difficult to tell in practice on real roads - too many other complicating factors. The other difference between adaptive xenon and LED is that the swivelling "looks round the corner" feature is replaced by a further LED set which illuminate when you turn the wheel significantly and shine on to the apex of the junction. How much you have to turn the wheel, and what range of speeds allow this to happen, I don't know but again, it just gives a bit more light where it might be needed.

So, any conclusions? Yes. LED headlights are very bright, and there are some clever features in there that try to give you as much light as possible without dazzling anyone. For the most part they succeed very well, and where they don't, you can always override them with the dip switch anyway. They can get confused with narrow roads and high hedges (I think that there is too much reflected light and the LEDs won't switch to main beam), when on main beam they can panic at the sight of a particularly bright reflective roadsign and dip, and the contrast between main on and off is quite marked - more so even than with xenon which themselves are quite bright on main beam. Also, the xenons vary continuously between main and dip where the LED main beam actually turns off, so there is a sudden change of light and only the dip beam has range-assist.

Would I go for LED again? Based on experience to date, yes, probably, but my couple of hours with an adaptive bi-xenon setup says that that is actually very good as well - main beam is not quite as bright but still very effective and much better than halogen, and the variation from main to full dip and back is continuous across the range where the LEDs have a discontinuity when main turns off. In terms of sheer light output, the LEDs win for night driving. If budget is a bit limited, go for adaptive bi-xenon and spend the money on other goodies (toys?).

One man's opinion - your mileage and eyesight may vary

[BigAid]

Thanks for a very comprehensive review nealeb


Sent from my iPhone using Tapatalk

[robbyg]

excellent science nealeb. I still dont know which to go for though. LED lights look cool, so i will probably go that way....

[nealeb]

LED lights look cool

After posting a few pictures, you may note that I have said nothing about cosmetic qualities! That's a personal opinion and not one that affects my own choice. Beauty is in the eye of the beholder and nowt to do with science...

In any case, the only reason that LED lights are cool is because of their fans

[Timothy Nathan]

Nealeb,

Where do pedestrians and cyclists fit into the scheme of things?

[nealeb]

Nealeb,

Where do pedestrians and cyclists fit into the scheme of things?

Do you mean what are my personal opinions of them, whether they should carry xenon or LED lights themselves, or are they detected by the adaptive light control subsystem? The last one is easiest to answer so I'll have a go at that one! Easy to answer because I don't know. In the same way that I don't think that motorcycles are reliably detected by ACC, I think that these other road users are below any reasonable detection threshold. And I didn't encounter any on my voyage of exploration the other night! I suspect that a really bright reflective jacket might trigger the auto-dip (main beam assist) function but given its sensitivity to road signs, not until it's too late. Don't know about an oncoming bicycle "headlight", even the brighter LED ones. Are you worried about following a cyclist and dazzling him with main beam or a too-high dip? Probably not as they don't have mirrors, in general, and may even be able to make use of your lights in that situation.

If there is anyone out there who would like to make a kamikaze run at the front of my car one dark night, on foot or on bike, to measure minimum detection range, I'm sure that we could set something up

[Timothy Nathan]

OK, maybe I wasn't specific enough. Any decent road user will dip for oncoming pedestrians and cyclists.

My worry is that Adaptive users will get out of that habit because they are so used to it all being done for them.

[nealeb]

Can't disagree with that, but to a certain extent the same is true of most of the driver aids that we see being fitted these days. ACC, anyone? I switch between the automatic A6 and manual A3 and Focus. Usually, I remember whether or not I'm in a car with a clutch or not...

Philosophical point - is it better to rely on other drivers knowing how and when to dip, or to give them something that gets it right nearly all the time? Given that the average driver doesn't even seem to know where the dip switch is and never, ever, uses main beam.

Further discussion point - also given that the average car user probably relies more on what the dealer tells them when they pick it up than on reading, understanding and using the driver's manual, how many drivers of a car with the complexity of the current A6 actually know what half the buttons and knobs do, let alone how to use them? Contributors to this forum excluded, naturally, as you have at least demonstrated some level of ability to handle modern IT systems!

[robbyg]

I am just wondering, i believe the individually moving up and down to shape the dipped (adaptive light) beam function is disabled for america (read off another forum). perhaps some VAGCOM tweaking can re-instate it here in the uk? I cant believe audi have designed multiple LED systems, it must be 1 system with several software variants?

[nealeb]

Robbyg - I'm not saying that the lights do not move separately, just that it's difficult to see if they do! In fact, with a bit more experience, I'm starting to think that I do see different beam patterns from time to time but I haven't been able to correlate with what in the environment might have triggered the change. Yes, I would be pretty certain that all the mechanics exist in all variants and it's only software that changes. That seems like the obvious way to do it, barring the addition of an odd cable perhaps. You need the motors for self-levelling and so on whatever else you do in the software, for example.

As for American headlights - haven't they just moved out of the "candles only" era and into the "you're allowed a torch bulb as long as it's not too bright" 21st century? I haven't been to the US for a few years now but I was always appalled at the poor headlights on US cars, and even more that this state of affairs apparently existed because of tight controls on what was allowed, even to defining the "standard" light unit at one time (the US official candle?).