idk, people die regularely while train surfing. One slip and you not only die but know what it feels like to have your extremities cut off. Extremely dangerous and not even easy to do, because train yards are camera controlled and because of many incidents the awareness and security on cargo train yards is pretty high. Trains do stop some times to let other trains pass and they do stand for hours sometimes, but since europe is so densly populated, you will constantly pass through train yards and stations. You would have to hide for hours, tensed up to not fall and deal with the constant loud noise of the trains. I would honestly rather pay the extreme high prices for tickets than to be in discomfort and the risk of dying for hours. Even if paying for tickets is not punk and the whole system behind it is totally corrupt and fucked.