AFAIK it's not epidemic to a degree that would require A) women-only cars B) guarded women-only cars as a placeholder remedy while societal attitudes shift in their usual glacial pace.
I'm not sure. Here (Germany), they already keep working at this issue - so far it's mostly cameras, better lightning, schooling of personell, re-doing access points, women-only parking close to exits, and so on. Stuff you don't 'really' notice. Japan chose women-only cars (usually only during rush hour) and an awareness campaign to combat this.
But I've seen studies that make claims like 60% of women being harassed in public transport. I've seen similar figures for Japan. But it's something they focused on, so it gets reported, and is in the news, and it's (sort of) visible with the women-only cars. But looking at actually persecuted cases:
"the number of reported indecent assault in subway carriages in Japan between 2005 and 2014 ranges from 283 to 497 cases each year"
... that's nothing. That's not even 0.0001% of passengers every year (Tokyo alone has 3.3 billion passengers per year in their subways...). And I suspect that's again similar to the West.
But, anyway, this is all off topic; sorry about that ^^;