There was one a movie I saw many years ago. I think it was about a woman who had an affair. I think the affair goes wrong and instead of going to her husband she decides to kill herself by throwing herself in front of a train. She is just about to do this when a hand pulls her back and it's her husband. I believe it takes place in the British Underground and it was filmed in black & white and may be from the forties.

"Anna Karenina?"