In May 2005, women-only carriages were introduced on the morning rush-hour trains of 10 major railway and subway operators in the Tokyo metropolitan region. This move came about after the Tokyo Metropolitan Government and the Metropolitan Police Department called on train operators to improve passenger comfort and prevent incidents of groping in the tightly packed morning commuter trains.

Other than children of elementary school age or below and disabled people and their carers, no men are allowed to ride in these cars, which are emblazoned with pink stickers bearing the message "Women Only" in both Japanese and English.

Most women welcome the move, saying that they feel safe and secure knowing that they do not have to worry about gropers. Pregnant women and those with young children are also happy, saying that other women who know what it is like to be in their situation are more willing to give up a seat to them. A mother who takes her young child on the train to a childcare center near her workplace every morning says, "I'm glad I can take the stroller on to the train without feeling awkward." Some men have also welcomed the introduction of women-only cars, because they no longer have to worry about being mistakenly accused of groping in the packed rush-hour trains. Others, though, of both sexes, say that women-only carriages are a form of gender discrimination, increase the crowding in other cars, and do not solve the fundamental issues.