It can be reliable, but like others said, if you don't want to involve others in your death, then it's better to choose a method that has a lower chance of traumatizing others. As far as reliability, it depends on how you hit the train (whether your neck was severed or just your body hitting it). If you survive such an attempt, you would likely end up losing many limbs, possibly even end up as a vegetable and life getting objectively and subjectively worse. Furthermore, some areas now have fences that close which would make it harder for (if not outright prevent) people to CTB via speeding trains, especially in the subway.