I have found a viable solution to highway glare that remarkably improves driving visibility in rainy conditions. I invested in a couple pairs of Polaroid clip-ons. They have been my means of survival in high glare conditions. I cannot recommend them enough to all my friends or to anyone who finds themselves having to drive in the rain, or snow, for that matter. I would even go on to say that they should be required of all drivers as using seat belts are. They make that much of a difference.
I have one pair that is a driver Serengeti and the other being a golden brown. I think I paid $30 for each. I use them both interchangeably and believe this is the best combination to have since not all lighting conditions are the same. Believe me, once you've tried wearing these, you would be convinced that they can make the difference between safe, comfortable driving and hazardous driving. I cannot stress enough the difference Polaroid technology has made for me.