Groping and verbal harassment is an exasperating reality for women using public transportation in this sprawling capital, where 22 million passengers cram onto subways and buses each day. Some men treat women so badly that the subway system has long had ladies-only cars during rush hour, with police segregating the sexes on the platforms.
But that hasn't helped women forced to rely on packed buses, by far the city's most-used form of public transportation - until this week.
Acting on complaints from women's groups, the city rolled out "ladies only" buses, complete with pink signs in the windshields to wave off the men.
As word spreads about the buses, the women seem delighted, while some men forced to wait a few minutes longer have shown their anger. Still others have stumbled on board despite the signs, much to their embarrassment.
On Thursday, passengers on one of the female-only buses spent most of their trip down the capital's tree-lined Reforma Avenue chatting or putting on makeup, instead of fighting off unwanted male attention.
When a man mistakenly climbed aboard, the women immediately began teasing him and shouting that he should read the "ladies only" sign.
"He's a gentleman! He should get off," shouted Yolanda Altamirano, a 64-year-old office janitor.
The man blushed and mumbled an apology, then ignored the taunts until he got off several stops later.
"Now he knows how women feel," Altamirano said, unapologetic for giving him a hard time.
Mexico City's female-only buses run along three busy routes throughout the day for now, but the city plans to add them to 15 other routes by April, said Ariadna Montiel, who directs the public bus system.
"Women were asking for this service because of the sexual harassment, especially groping and leering," Montiel said.
And while some men have complained that they have to wait longer for a bus, she said the women are thrilled: "The women are really happy and we have been getting a lot of e-mail and letters from them."
Juliana Romero, a 49-year-old secretary, said not riding with men is "fantastic."
"When the bus is packed, there will inevitably be a lecherous man who will bother you," she said.
Women-only buses or subways have been rolling for years in India, Brazil, Japan and other countries. Mexico City finally took the action as part of a growing responsiveness to complaints about discrimination against women, Montiel said.
While only seven female public bus users complained last year, she said the real number of offenses was probably much higher, because women rarely protest openly against sexual harassment.
Some women, like Maria Elena Sanchez, have learned to take matters into their own hands. A 47-year-old office messenger who uses public transportation all day, said she carries a sewing pin for protection.
"I always carry the pin so I can defend myself from abusive men," she said - adding that she's had to use it twice this month alone.
Traveling only with women, she said, makes her feel more secure and allows her to relax a bit on the way to work.
"I don't think I will use the pin on these buses," she said, giggling.