This is not original with me, but wnen polarizing film was first introduced to the public in the 1939 New York World's Fair, it was suggesred that the film be used on automobile headlights so that the "grain" of the polarizing angle was 45 degrees to the horizontal. A similar sheet of polarizing material in the same orientation would cover the windshield This would only slightly interfere with the brilliance of the beam for the driver of the car, but a car driving n the opposite direction would have the polarizing "grain" at right angles to that of the oncoming car's windshield, and the light would be severely dimmed. This would effectively eliminate the blinding effect of headlights on oncoming cars. All cars would have to be so equipped for the effect to function, but it would make night highway driving much more pleasant.
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This idea didn't take effect when it was first proposed around 1939 because most cars would have had to be converted to this system in a short time, and this wasn't feasible. I think the same issue would prevent this idea from being put into effect today. Here is another problem: You depend on seeing oncoming headlights far ahead when driving at night. This system might be too effective at blocking the light from oncoming headlights, such that you wouldn't see oncoming cars until they were dangerously close.
If putting the polaroid film on windshields is too expensive and problematic in deployment, how about putting said 45 degree angle film on "night driving" glasses? You could even make the angle adjustable for allowing better distance detection of oncoming traffic, but (like the dimming of rear view mirrors) could cut glare down for safety as they approached.
This leaves the biggest expense and probem of how to retrofit all these new headlamp lens styles... putting the filter (assuming it would take the heat) on/around the lamp element would not work as the various reflectors change the polarization angle differently in different places. Putting a filter on the surface is next to impossible with the compound curves, and every new style seems to be unique... Remember when all headlights were pretty much uniform by law?? Makes one realize that progress to some point is always also progress away from some other possible points.
I already wear amber-tinted, polarizing lenses for night driving. Applying a polarizing filter membrane over all the vehicle headlights in the world is all that's needed to complete this idea.
The angle of the crystal orientation in ordinary polarizing sunglasses is probably not at the proper 45 degree angle necessary for headlight blanking in conjunction with 45 degree angle polarizing film placed over headlights.
One massive problem with this idea is that a polarizing filters by nature block half of all light coming through. This would be akin to putting a 50% tint on your windshield (which is illegal in most places for good reason). Not only that, your own headlights would also be 50% dimmer! Since only half the light from your headlights would get out, and only half the light from the road would get into the car, your headlights would need to be 4 times higher power, and the streets lights would have to be double the brightness just to see as well as before.