This doesn't strike me as much of a solution. As Jessica Valenti observes in The Nation, "I'm all for safe spaces for women, but is segregation really an answer to sexism?"
Singh noted in her comment that getting on the woman-only bus was always a relief, which I can certainly understand: When I was in law school, we had a women's lounge -- a restroom that included a large area with couches, comfy chairs, and tables -- and it was always a relief to hole up there to study. We weren't hiding from gropers (though there may have been a few), but from the pressure of continually fitting into what was decidedly a male-dominated world -- our class was about 10 percent women.
A recent study highlights the fact that women are still in a double bind when dealing in the world: do things the way men do, and you're labeled unfeminine; do them in a more feminine style, and you're too soft. Just ask Hillary Clinton. So the occasional respite into a woman-only world does provide some relief.
But protecting women by segregating them from men leads to protecting them by keeping them out of some professions and public spaces. It reinforces the idea that women are helpless. And it limits the lives of the victim of abusive behavior, instead of stopping the abuse.
Besides, the bus isn't the only place where women get harassed. The Washington Post reports that a man -- or perhaps, judging by the varied descriptions, several men -- has been been attacking women in Northern Virginia. The police haven't caught anyone, and women are responding by taking cabs and giving up walking. Of course, cabs are expensive and walking is good exercise, so fear is taking a large toll on these women's lives.
I haven't noticed any cities declaring streets off-limits for men.
Judging from the description of the attacks, I suspect most women could fight this particular attacker off if they had a little training. He's apparently not using a weapon. But the article doesn't even mention learning how to fight as a solution to such attacks. It's not the only answer, of course -- good lighting, regular police patrols, and a societal decision to take such attacks more seriously can all improve safety.
But women can learn enough to protect themselves from such attacks, just as they can develop skills to deal with gropers on the buses. In Singh's comment, she noted that she developed a tough style when riding on mixed buses in New Delhi (though she found it a relief when she didn't have to do that). Making a scene is also a reasonable response.
Women taking action to protect themselves, whether from gropers or rapists, will eventually provide more safety than token respite on public transportation. After all, as the Valenti article notes in a quote from Katha Pollitt:
Obviously, there would never be enough women-only space to accommodate all women all the time - half the subway cars or half the hotels …Women-only space is just a little breathing place for a few women every now and then.