This is the key, right here. What many people don't understand (or don't like to hear) is that we are not dealing with a 1:1 safety issue here where a unit of extra seeing light and a unit of extra glare light cancel each other out, safetywise. In fact, the safety benefit of additional seeing light is massively bigger than the safety detriment of additional glare. So much so that good quality research on the subject (by UMTRI, a very reliable group of scientists in this field) concludes that safety would be improved -- meaning fewer crashes, less injury, fewer fatalities, less property damage -- if everyone used high beam after dark, even in traffic. The researchers acknowledge, however, that this would be very uncomfortable and so would not be accepted in practice.
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Virgil,
Can you point to this study? How recent is it?
It seems to me that it is an older study, and doesn't take into account the blindingly intense lights of today. You see... 20 years ago, high beams may be uncomfortable when aimed into the face of oncoming traffic, but they would not necessarily be blinding. Today's lights are absolutely blinding.
There is a fairly brightly lit intersection in a town I drive home through at night. Typically there is a stream of oncoming cars stopped at a stop sign, on a slight rise in the road, and their headlights (properly aligned) hit me directly in the eyes. I slow to about 5 mph because I might not see a pedestrian, crossing the street, in front of me.
There are another couple of spots on the way home, that are hilly, and the road curves. In these sections, the road is very dark, and my eyes are a little dark adjusted. Often, suddenly as I approach this curve, an oncoming vehicle comes up the rise, with it's beam in my face, such, that I have to look away, and judge, that I am staying in my lane, by looking to the right hand side of my lane, for where the asphalt meets the dirt. Sometimes, the light is so blinding, that I have to hit my brakes, and am afraid, that I might be rear-ended, because the driver behind me, may also be blinded, and not see my brake lights.
I often have a vehicle behind me on the interstate, that is literally 1/4 mile away, and its headlights, lights the interior of my cab sufficiently, that I can read a gas station receipt. I can not believe, that much light, and with that much intensity, is needed to increase safety.
Back in the seventies, I took a driver's safety test that warned driver's: Do Not Over-drive Your Headlights. In other words, do not drive faster, than that speed, which would allow you to stop, within the distance, that you can safely see with your headlights. They also pointed to driving around blind curves. They also pointed to using low beams or fog lights, and NOT high beams, when driving in fog, AND that people have a tendency to drive faster in fog, than they should, because (they proposed) that when in fog, people lose some of their sense of speed because they can't see very far into the periphery. All this to say... people need to be cognizant to their surroundings, and not excessively speed just because they can.
Did the researchers take into consideration that many of the fatalities, that occur at night, are related to alcohol consumption?
It seems to me that the study you refer to is flawed. If not, does it suggest that I should increase the output of my headlights and drive with my high beams on? Does it mean that I would no longer be blinded if doing so?
Driving blind can not be a good thing.
