Though I can't quote statistics, my sense is that once a region reaches are certain critical mass of commuters, the number of women who decide to become commuters themselves increases dramatically.

Outside of winter, there are probably more women than men who commute in my office. A large part of that is that we're a non-profit that specializes in energy efficiency. We have a significant number of female employees who are relatively young, live in the city, and appreciate the low impact that cycling has on the environment. It's not just young women though. Until she retired, probably the biggest cycling advocate in the organization was a woman in her 60s. There are also a lot of male commuters.