Japan has one of the highest suicide rates in the world, somewhere around 7th or 9th highest in the world in the last few years. It's widely considered a national issue, because it's the leading cause of death among men aged 20 to 44.
It doesn't help that culturally, suicide is considered a morally responsible action in certain cases. The economy, depression and social pressure are some of the highest reasons for suicide. 71% of suicides were male in 2006.
Jumping in front of a train is a popular way to end your life in Japan. It's considered to be practical and nuisance free to the person's family. However, it isn't for the train companies. A person committing suicide can slow down traffic for a few hours.
To dissuade people from doing this, train companies have begun implementing certain measures to lower the number of suicides. One is fining the decesed family members. They can be charged up to 1 million yen, or $12,000. They've also begun installing blue LEDs in stations, which can have a claming effect on jumpers. Another method they've begun testing is having station doors that contain people until the train arrives.