I drive to work along the same stretch of road everyday and I've started to notice a pattern in some of the accidents that occur: the low sun. For long stretches the motorway runs almost directly east-west and so you end up being hit head-on by the blinding rays, all it takes is someone to slow down while your vision is impared an bang, multi-car pile-up. Add to this that over the autumn/winter/spring months the roads are covered in salt, there's spray from other vehicles due to rain or thawing frost, more chance of heavy rain and your windows constantly mist-up due to the temperature differentials and you can see why it's a recipe for pile-ups, sometimes the cars in front just disappear as the sun catches you dead on and the salt on your windscreen goes opaque. The problem isn't helped but the seemingly random queues that appear or the hills, which the sun hides behind until you crest it and then hits you full on.
So, aside from windscreen washers which work in sub-zero temperatures that would let you shift the salt build-up and a windscreen with anti-misting agents layered on the inside, I have another idea: polarising filters on your windscreen. What I'm talking about is something that would react to the sunlight and filter it so you can see no matter how bright it got. To be honest, it doesn't need to be on the windscreen, we all have sun visors in our cars these days, but they're useless if the sun is too low. Instead of making them simply solid material, why not make them out of some sort of filter with the option of making them completely block all light, or act as a filter so you could have them fully down and see through them? Go one step further with the idea and you could add the some sort of enhanced viewing mode (with an infrared light or the equivalent of a starlight scope on the from of your car) for night-time driving.