I parked my car under a tree Sunday night and had much less ice as a result but a tree was nearly in the bed of my truck by morning. I scraped the ice off my windows and covered them with plastic after I parked my truck away from trees. When I had to take my wife to work Tuesday morning I had ice on the roof. I tried to remove it but it was rock solid. NO WAY it would fly off and hit anyone if I could not bust it off with a tire tool. I did not use the freeway. I saw probably less than 10 vehicles until I was closer to downtown where we were running much slower. I have 4x4 and snow rated tires but decided to just run a safe 30mph max anyway, because the wife was freaking out. I experienced no sliding and never felt a tire spin. I dropped the wife and went to a grocery store that was open. By this time, the sun had come out. I parked the truck in the sun with the intention of trying to clear the ice away when I got out. Now I had a thoroughly heated cab and the sun to help. Experience told me I could get the ice off. I took my time in the store because I knew I had nothing else to do. Paid for my items and had some fuel points to burn so I fueled up before I left too. I drove out onto Franklin and realized "OOPS! I forgot to get that ice off the roof!" At that same moment, I hit the brakes to turn into the nearest parking lot I was about to pass up. The 2 inches of ice on my roof slid off in a solid sheet onto my windshield IN TACT somehow. It blocked my whole view! It was not a big issue for me. Nobody else was on the road. I simply jumped out and easily broke the sheet at a gap between it and my window and removed enough to see how to get off the road. HOWEVER, it could easily have been a big deal! If you catch enough sun and have a good enough heater to melt the bottom and the sheet becomes detached from the roof, it can fly off and hit someone. It is not going to kill any other driver unless they wreck. It will break up on impact, but it could cause an accident or dent a car! It could also slide over your windshield at 50 or 60 mph on the freeway (which has been mostly cleared) when you tap the brakes. Do you want to be blind at 50MPH? Your first thought will be "I can't recall if anyone was in front of me". I can understand NOT being able to remove it. I have had this happen in other areas several times. But REMEMBER to check if you can remove it later and NEVER get on a freeway or run high speeds if you can't. If your heater is going, the heat rises. It will warm the ice from the bottom and make it become loose. Get up early, idle the vehicle with the heater on blast if possible. I should have left myself note on my wheel to remind me to try to remove it after the sun was on it. I was never going to go anywhere I'd go fast enough it could have gotten airborn but I did let it obstruct my vision for a few seconds. VERY STUPID OF ME! Also, if you are stupid enough to drive fast enough to send ice flying through the air, it may not kill another driver barring a traffic accident but in my neighborhood, on the 18th, I saw MANY people walking to work. A flying chunk of ice 1x1ft could potentially kill a pedestrian. It may not be likely but it could happen. Also, use caution and follow at a much greater distance in ice and snow. BE PATIENT! Same goes for passing a person. Don't get in a hurry and pass beside another driver. Make sure you have a lane between you both.