I drove through a 500 mile blizzard (or it seemed like it) at night (damned stupidest thing I’ve ever done, and I’ve done a lot of stupid things), and my headlights froze over with about an inch of ice. This turned the light into something like a hazy corona. At the time, I’d have paid you all the cash I had for headlight wipers.
As an aside, the Volkswagen Phaeton comes with washers that clean one headlight at a time, so that you don’t end up with a brief moment on dimmed headlights. Along the same lines are the windscreen wipers that lift briefly before changing direction, just so the blades last a little longer.
And if less light is escaping, that means more heat energy inside the bulb. I’m gonna take a WAG and speculate that the wipers are mostly about preserving bulb life against heat degradation.
Well, If you can convince my boss that we should only drive the trucks during the six hours of daylight we get right now, I’ll buy you a beer.
No, it was specifically listed as a safety item when introduced.
My wife’s Volvo v40 has them. My experience is that they don’t work very well. The springs in the wiper arms get slack and then they don’t contact the lights. Also, the car uses up washer fluid like crazy because of the extra two spray nozzles. They were part of a “winter package” that included heated seats and traction control.