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Comment by lttlrck | Hacker News Reader

Fogs lamps are worse for the person using them than oncoming traffic. This is due to the way the light is focused. It's directed downwards to avoid the light reflecting straight back into your eyes off the fog or snow. This is what makes them different. However it affects your ability to see far even if you have your high beams on.

I remember reading about this in an article written by a rally driver in ADAC magazine maybe 20 years ago now.

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If we're talking about our own vision rather than another driver's, yes, fog lamps might detract a bit from our night vision. The truth is, if you're using them in an actual fog, your distance vision is fucked anyway, and it's your regular headlights (which do not power off when the fog lamps are on) which are doing the damage to your night vision, since they're focused at eye level and reflecting back. The fog lamps aren't a big worry in that regard.

> I remember reading about this in an article written by a rally driver in ADAC magazine maybe 20 years ago now.

I've seen those arrays of fog lamps installed on rally cars, and I'm not sure what they're about but they're a pretty different paradigm than anything that comes installed by the factory on a passenger car.

Re: rally car lighting

They're not the same light pattern as fog lights (well, not all of them). Some are "pencil" beams that reach far, some are closer to fog beams for close-in. Coverage is the name of the game.

They need them because the goal is to be driving as fast as possible, so you need as much light as you can get onto and down the road.

The reason they're on pods on the hood is because they're removable. They only put them on when needed, because they're very expensive and you don't want them getting damaged when not in use.

Ah, this makes sense. I've heard about the phenomenon of drivers of regular (not rally) cars driving so fast that they outrun the range of the headlights, such that even with perfect reaction time they are not able to stop or react to something on the road ahead. Simply increasing the brightness of factory high-beams must only get you so far.

Rally car lighting systems have more in common with aircraft lights. The landing lights on a 757 are standard GE units with 600w, 28v, bulbs, costing $50, that produce 750k candle power. Narrow beam. As bright as the sun. Wider beamed taxi and runway turnoff lights still use 450w.

ACLs see some use in concert lighting as well. They're not just for aircraft! (and rally cars)

I use my (factory installed) fog lights only when the conditions are bad enough that I need a downward facing light to be able to see the lanes or obstructions. mine turn off if I turn on high beams, which do not have the very close reflections. they make a significant difference in specific circumstances. why I see some people drive with them on under all conditions, I will never know.

I discovered the fog lights on my new-to-me vehicle recently and use the lower ones (the upper ones are burned out and need replacing) at night to illuminate the near road better and make it easier to see and avoid holes in the road.

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