In the UK, I read that the problem with wet leaves is growing because they don't cut trees back so much on the sides of train lines to be more environmentally friendly. In the days of steam trains, they had to cut right back because of the risk of fire. now they let trees grow for the environment and more leaves fall on the line. Many people regard it as a silly excuse for our chaotic train system, but, according to what I read, there is a genuine problem. ;-)