Women only passenger cars is like trying to fix a problem without addressing the root of it. Women shouldn’t feel the need to have their own passenger cars. They shouldn’t feel threatened where they live, as nobody should. If women have to have their own segregated spaces then there is a cultural and judicial problem to be addressed.

Your question seems to presuppose women will always need to have their own segregated spaces and the causes of that need are intrinsic to human nature.

Crime is a disease of capitalism. The willingness to do harm is systematic to social alienation. We don’t kill people but we kill animals because there is an alienation between us and the beast. The willingness to exploit comes from the trauma of exploitation. The willingness to treat people as cheap commodities comes from the commodity fetish.

Likewise look to your super structure. When you alienate women from their identity beyond a replaceable means to a sexual end, and when you represent the female body as a consumable commodity object to be bought and sold, then you’ll need to have separate cars.

Treat people with the dignity owed to them and present people as dignified and worthy of the same attention and respect due all people. Cultivate the community and allow people to feel as members of a greater whole whose needs and concerns are met and respected, and then you can ride the train next to each other without fear that your neighbor will harm you.