Or were they just a fad? I'm referring to the ones that replace sealed high beams.

 

I was interested in the answer so I googled it. Here is a copy/paste...
Scientifically speaking, there is no good reason why fog lights are yellow and not red. Here is an excellent explanation provided by Professor Craig Bohren of Penn State University:

"First I'll give you the wrong explanation, which you can find here and there. It goes something like this. As everyone knows, scattering (by anything!) is always greater at the short wavelength end of the visible spectrum than at the long wavelength end. Lord Rayleigh showed this, didn't he? Thus to obtain the greatest penetration of light through fog, you should use the longest wavelength possible. Red is obviously unsuitable because it is used for stop lights. So you compromise and use yellow instead.

This explanation is flawed for more than one reason. Fog droplets are, on average, smaller than cloud droplets, but they still are huge compared with the wavelengths of visible light. Thus scattering of such light by fog is essentially wavelength independent. Unfortunately, many people learn (without caveats) Rayleigh's scattering law and then assume that it applies to everything. They did not learn that this law is limited to scatterers small compared with the wavelength and at wavelengths far from strong absorption.

The second flaw is that in order to get yellow light in the first place you need a filter. Note that yellow fog lights were in use when the only available headlights were incandescent lamps. If you place a filter over a white headlight, you get less transmitted light, and there goes your increased penetration down the drain.

There are two possible explanations for yellow fog lights. One is that the first designers of such lights were mislead because they did not understand the limitations of Rayleigh's scattering law and did not know the size distribution of fog droplets. The other explanation is that someone deemed it desirable to make fog lights yellow as a way of signalling to other drivers that visibility is poor and thus caution is in order.
Designers of headlights have known for a long time that there is no magic color that gives great penetration.

 

That's about what I thought when I found out they don't make rectangular fog lights. The ones they sell new are only for "period accuracy".

 

Dr. Bohren has extensive knowledge of the physics of light and how it interacts with our environment. I know that all he says is correct from my own scientific education.

However, he is not a physiologist. The answer to this question belongs in that realm; it concerns how our bodies react to our environment.

There are two effects of blue light to consider:

• The eye processes different wavelengths differently. The blue parts of the spectrum are focused at the leading edge of the retina, and not on the retina. This results in a blurred image. You may have had the experience of looking at a deep blue business sign at night. As you get farther away, the sign blurs and it is not possible to read it.
• The pupil does not react sufficiently to blue light. This is the reason that many HID and LED headlights cause so much glare. The glare is not from your advancing age. The glare results from your pupil not constricting, which allows excessive light to reach your retina.

It is true that filtering the blue spectrum from a light removes around 12% of the light. But we can't tell the difference in intensity until the light loss gets above about 15%. And our eyes can't tell how well we can't see. We only notice what the illumination shows us.

Physiologically, the loss in light intensity of a selective yellow light is outbalanced by our better-focused vision and the better reaction of our pupils.

 

No lamp of any color installed and adjusted as a high beam will work as a fog or driving light. Fog lights are low beams, mounted the lower the better on the vehicle to see with.

 

So that is why the LED emergency lights on police vehicles and first responder vehicles blind you from dusk to dawn. Officials pass the Move Over law in every state but do nothing to ensure motorists are not blinded by the same vehicle they are now required to safely pass.

Some states have headlamp laws that require headlights to be lit a half an hour after sunset and a half an hour before sunrise. This was done to allow the vision of motorists to adjust to the dim sunlight.

Motorist pupils are dilated during those periods trying to use the dim sunlight to see. Use of headlamps only blind oncoming motorists - when there is enough natural light to operate a vehicle, with just marker lights on, and fog lamps if equipped, to assist with seeing vehicles. One vehicle using headlights during those periods causes other drivers to need their headlamps on due to their pupils being temporarily constricted.

 

Do I get some kind of certificate after reading all this stuff. Ontario law has us turn lights on I/2 hour before sunset and 1/2 hour after sunrise.

 

This is actually the law in most states in the US also. I thought Canada required driving lights for late models?

 

No Eric. You might be getting this mixed up with DRL (Daytime Running Lights) which has been mandatory in Canadian production for decades.

 

That's what I meant Allan, I should have reread my post.

 

Eric there's a move afoot to change production standards so that DRLs will also require taillights to be lit. Too many dorks driving around with only DRLs on. You'd think they would get the hint if their dash isn't lit wouldn't ya?? My wifes old Saturn has a green DRL that turns off when the headlights are lit. Kind of a heads-up for the driver. For me it's a no brainer. I drive with my headlights on all the time. Easier to be seen. My sons Malibu has automatic headlights and DRLs but no dash symbol.

 

Seems that on most of the new stuff, the dash lights are on all the time. So these idiots drive around in the rain and snow and especially the dark, without any running lights...duh.

 

With the increase use of factory LED & HID headlights, as well aftermarket conversion LED & HID headlights, it would be thought a law requiring headlamps be on a 1/2 hour BEFORE sunset until a 1/2 hour AFTER sunrise would make matters worse regarding blinded motorists.

In the US, most states require headlamps be lit from sunset to sunrise, or when visibility is less than 1000 or 500 feet, depending on the state.

Some states require headlamps be on from a 1/2 hour AFTER sunset until a1/2 hour BEFORE sunrise, which properly allows for motorists vision to safely adjust to the dim light during those periods without oncoming headlights causing temporary blindness.

The Wipers On/Lights On regulation, now law in most states, further contributes to the phenomenon of headlights blinding motorists. Motorist eyes are adjusted to the grey overcast condition, but their vision is blinded by light from oncoming headlamps. With a drizzle or steady rain, a vehicle's marker lights and fog/driving lights (if equipped) are sufficient to see other vehicles. Headlamps should only be required during a heavy downpour, when wipers are set on high. The law should be amended to reflect the aforementioned and contribute to lessening instances of headlight blinded motorists.

 

Ontario used to have after sunset and before sunrise but it was changed to before sunset and after sunrise maybe ten or fifteen years ago. Probably because it is not always bright and sunny around here.

 

Driving thru the mountains of West Virginia one foggy nite ,I turned my headlights off. Drove withe just the yellow parking lights. Visibility with headlights may have been 50 ft.. With just the yellow parking lights I could see enough to drive 50 mph.. 81 chevy pu has park lights about 5x6 with 2 1157 bulbs

 

Yes, a thinking person's certificate.

I am continually amazed that I learn something new almost every day on this site and I am happy to contribute whenever the discusion leads in a direction I have knowledge about.

Now if you were corresponding on a Mustang or Camaro site, you could get a certificate for your expertise in throwing verbal grenades at other site members.

 

Yes, they work very well IF you buy the proper lights and adjust them correctly
https://www.tapatalk.com/groups/real...0.html#p117329

 

I have restored a mustang and a porsche before my 442. I am amazed every time I am on here how open minded everyone here is. My previous experience with these sites can pretty much be summed with if you don't know, then you shouldn't be doing it. Instead I get to read kick *** posts like this one. Almost as good as the one on blue dots, or full voltage to a coil.

 

Agreed. My "new" car, which is a Volvo from Sweden, has front fog lights mounted in the lower portion of the bumper, about 12" above the ground. They are white (clear) spotlights. The rear fog light is an amber (yellow) light mounted at the highest point in the tail light assembly, so it has the best chance of being seen from behind.

 

Fog lights are very wide angle and are usually up too high which blinds oncoming motorists. Fog lights should be at the top of the grille, pointing aggressively downwards. It is hard to get low slung lights to do what you want in terms of coverage without too much angle.

 

Problem with fog lights is morons who use them all the time as driving lights.

 

When the term driving lights is used in this context, they are auxiliary lights, not headlights. Not sure if that was what you meant when you mentioned driving lights, which also sometimes refers to headlamps.

 

Anthony - Yup. I realize what headlights are. Maybe different terms than what you're used to. So what I was getting at is the morons who always use the fog (lower lights intended for fog/snow etc) all the time when it's completely unnecessary. And then there's the idiots who never use their headlights/driving lights when they should (low light conditions or bad weather). Where I live it's kind of an epidemic that's gone unchecked.

 

The only car I've ever had that the fog lights did anything other than just look cool is my 2011 Impala. They actually light up the road immediately in front of me and often negate the need to turn on the high beams. The super bright LED headlights on a lot of cars today really irritate me. There should be a limit to the lumens a car's headlights can put out. I also keep a pair of yellow shooting glasses in the car to wear at night when the glare gets to me.

 

There is a lumen limit, and it is less than the European limit. The difference is that Europe requires strict control of stray light above the car centerline (glare); whereas, US regulations allow a lot of stray up-light because they say that is necessary to read overhead signs, although Germans don't complain about seeing overhead signs.

European cars with high-lumen lights must also have a built-in headlamp-lens-washing system because dirt on the lens can also cause glare to other drivers. In all, European headlamp regulations have addressed glare.

The summary for this country is that regulations have allowed higher lumens without addressing glare problems.