I was doing about 80 when the hood popped up. Had just been in the shop, and I don't think was fully locked. Strange in a very scary way.
In the first car I had at age 16, the hood slammed against the windshield, though the windshield didn't break, the hood was pretty bad looking afterwards. No clue how fast I was going, as the speedo was broken since the day I bought it. You could see beneath the hood to pull off the road but it was pretty damn scary. Kinda funny in retrospect but only because nobody was hurt.
TD