I read this story maybe 20 years ago. It's about a woman who has a really fast car, and she goes on wilder and wilder rides by herself in the country. The story is told by a narrator who goes with her sometimes. There is this one place in the road where things start getting crazy - sort of like they're going so fast that they pass into a different dimension and there are weird things that grab at them. In the end the woman goes off on a drive by herself and never comes back. I thought it was a Roald Dahl story, but I can't locate it. Also I thought it was called Mrs. Somebody's? Wild Ride but I can't find that either. Thanks for your help.