Women only... in Brazil

I was watching the news today during lunch when I saw something that reminded me of Japan. Many people know about the "women only" cars that exist in many railways, especially in big cities such as Osaka and Tokyo. I was even asked about those cars after returning to Brazil ("Have you entered one?", "Are they 'women only' all day long?" and so on...). But I didn't know that such cars also existed here.

So, according to this article (link in Portuguese) this system is being implemented in some trains and subways in Rio de Janeiro (double surprise... are trains used so much there? If someone in the known could answer me I'd appreciate it) and, as the system is new, some problems and misunderstandings are happening. The worst of them was when a group of students entered the car without knowing it was "women only". Security forced them out, almost pushing one to the rails. According to one of the students, the request to leave was made only five stations after they entered the car.

Also, the article mentions a similar attempt made some years before in Sao Paulo, where some cars were reserved to women, elderly, children and handicapped. But since it wasn't respected, those cars disappeared in two years.

... Well, out the part that it wasn't respected in Sao Paulo (I'm not impressed...), I was surprised that such thing existed also in Brazil. In Japan, the main reason for the "women only" cars are the problems with gropers. I wonder if it's the same case here... I'm not sure... Just don't think it's likely... The article doesn't give the reasons.

And do other big cities around the world use that system too? I wonder...