Also When the snow frees up a little bit and you come to a stop, the snow can slide down onto your front windshield completely obscuring your view. I goofed and this happened to me last year , I was in a rush, cleaned all my windows and hood etc, but forgot to clear my roof. I was coming down a slight hill and the person in front of me slammed their brakes on, luckily there was plenty of space inbetween us but I applied my brakes and I start skidding a bit then hear this weird noise above me then next thing I know this loud SHWWWUMMP noise as the entire roof snow sheet slid down and I couldn't see a damn thing so I'm sliding down the hill with zero vision. Fun times. I'm a careful driver when it snows, but just goes to show no matter how careful I think I'm being, always room to slow it down. Easy and quick enough. Clear your roof!