Since 2000, the Keio Sen railway line in Japan has designated the last car of every train to be women only. The policy stems from efforts to prevent sexual harassment. Following the Japanese model, Taiwan Railway implemented a similar policy in 2006. However, there were conflicting voices regarding the legitimacy of the program, and the Taiwan Railway eventually suspended it after a six-month trial period. We believe that the implications of initiating such a program warrant detailed scrutiny. As a policy of spatial segregation, does it fulfill the aim of gender equity or become an obstacle to it? This paper first reviews three models of gender equity: sameness, difference, and transformation. Then, the authors analyze various discourses on women-only car policies within the framework of the transformative model. These discourses can be divided into formative equality, protectionism, separatism, and diverse society. We do textual analysis on the first three discourses and indicate the reasons why the fourth, ”diverse society,” fulfills better the agenda of transformative gender mainstreaming. With the global trend in gender mainstreaming, an increasing number of government policies and programs are planned and initiated in the name of ”gender equality.” But they are not unproblematic. We deliberate on the women-only car policies and analyze various public discourses. We propose that future gender policies and programs should be critically examined in the same manner, so as to continue the transformative and progressive spirit of gender mainstreaming.