About 6 years ago, driving over the Pennines (range of not-quite-big-enough-to-be-mountains-but-still-very-steep-and-craggy hills in northern Britain for those from overseas) from Manchester to Sheffield in the passenger seat of my mate's old Vauxhall Belmont (with him driving), in December, at about 11pm. Going round a very shallow corner at about 30-40mph, we hit some ice and the car just went straight on, off the road and down a grass slope, still doing the same speed through the dark over the field for about 100m until we met a fence at about 30 degrees to the car's direction, which caught the car, turned it slightly and we scraped down the fence before coming to a rest.
We both sat there for a minute in silence, then got out and had a look. The car wouldn't start, but wan't in too bad a shape externally (afterwards we found out we'd hit some rocks on our jaunt over the field and knocked the bottom off the engine). We called the police, then his dad and followed the tyre-tracks we'd made in the field back up to the road and waited for the authorities, and our lift home.
We went back in the morning the next day to have a look at the car and were absolutely *horrified* to find that the fence we'd hit was just thin wire held up with wooden stakes, on the other side of which was an almost sheer drop of about 50m onto rocks. The realisation of that was far scarier than the crash itself, I was almost sick.