The women-only cars are only during certain times of day. Read the sign and it'll tell you: basically it's only during rush hour. Also, the women-only cars are at the ends of the trainset.
There are certain cities that have made their women-only cars 24/7. More or less because the level of traffic they experience doesn't really make the loss of 1 car to 50% of the population any real detriment.
