As the mother of a teenage boy, I HATE the idea. he would be so much less safe on trains.
You think it is women's responsibility to share train carriages with men who molest us, just so that your precious boy is safe?
There's an interesting parallel between your opinion and that of those who want transwomen (=males) in women's prisons.
If your teenage boy is so nice and perfectly safe to be around, then why are other teenage boys and adult men not?
If you really believe that males are so violent that a males only train carriage would not be safe for your teenage boy, why do you want women to share train carriages with men?
Let's be consistent here!
I say, an experiment should be made.
If women-only train carriages are actually safer, then that teaches us a lot about men and their willingness, or lack thereof, to step in when other men molest women.
Likewise, if a males-only carriage would be a hellhole of violence, that would also be pretty telling.
And maybe make some people see that something needs to be done about the problem of male violence.