Let me say up front that, yes, riding on the roof of a train is dangerous. There are few good answers available to the authorities when it comes to putting a stop to this practice.
Having concrete balls hit human beings on the head is not one of those answers. This is draconian and frightening.
Somewhere, an Indonesian bureaucrat is tickled pink that someone finally listened to one of his or her draconian suggestions. This is what makes a place very difficult to live in, and you have to ask yourself this about your town: are the people running it as stupid as this?
If so, you have to move.