Did a quick google search which shows me that the following countries have women only carriages: Japan, India, Egypt, Brazil, Mexico, Indonesia, Phillippines, Malaysia and UAE
http://en.wikipedia.org/wiki/Women-only_passenger_car#IndiaI understand why some of these countries have it as inequality and sexual harassment levels are high in their country and some of these countries don't have as much equal rights for men and women like here in the UK. E.g. India, Indonesia have way higher sexual harassment levels and are more dangerous than in the UK, but it's not like sexual harassment is rife in the UK.
For countries like the UAE or Egypt, due to religious and cultural reasons which is why they have separate areas for women. They have always had it and I guess it works because these countries enforce it pretty well.
For Japan, I'm guessing it may work better in japan than the UK as Japan is having a population decline. (i'm just suggesting that maybe that may be a factor, not a definite cause)
http://www.statista.com/statistics/263746/total-population-in-japan/But then again, japan is way ahead of us in terms of technology and maybe they're just enforcing it well.
I personally disagree with women only or gender specific carriages. Especially in the London underground. The london underground is way tooo crowded. And what if you're travelling with your girlfriend/boyfriend, or family members or group of friends? What about a mother travelling with her teenage son? or father and daughter?