WOMEN have been driving yellow cabs in New York since the 1940s, but 99% of drivers are male. Even among drivers of cars booked by phone or online, only 4% are women. That may change with the launch of SheTaxis, an app that lets female passengers insist on female drivers, and vice versa.

It will be available in New York City (where it will be called “SheRides”), Westchester and Long Island, and the firm plans to expand to other cities. Stella Mateo, the founder, is betting that quite a few women are nervous and weary of getting into cars driven by men. The service may also appeal to those whose religious beliefs forbid them to travel with unrelated men. Each driver wears a pink pashmina. Men who ask for a ride will be directed to another car service.

Similar services thrive in India, South Africa and several Middle Eastern cities. Some Brazilian and Mexican cities offer women-only public-transport programmes known as “pink transport”. Japan has had women-only railway carriages on and off since 1912. Known as hana densha (flower trains), they offer a haven from the gropers who make rush hour in Tokyo so disagreeable. Women-only hotel floors are popular, too.

But SheTaxis faces two speed bumps. One is practical. Demand has been so great that the firm has had to decelerate its launch until it can recruit 500 drivers. The other obstacle is legal. By employing only female drivers, SheTaxis is obviously discriminating against men. Since anti-discrimination law is not always applied with common sense, that may be illegal. And there is no shortage of potential litigants. Yellow cabbies are furious at the growth of online taxi firms such as Uber. “It’s not hard to imagine a guy...filing suit,” says Sylvia Law of New York University Law School. SheTaxi’s defence would probably be that its drivers are all independent contractors.

Because the firm caters only to women, it is discriminating against male customers, too. Is that legal? Angela Cornell of Cornell Law School thinks there could be a loophole. New York’s Human Rights Commission could make an exemption on the ground that SheTaxi offers a service that is in the public interest: women feel safer not getting into cars with strange men. Women-only colleges are allowed, so why not women-only cabs? The snag is that some men may also feel safer getting into cabs with female drivers. A study in 2010 found that 80% of crashes in New York City that kill or seriously injure pedestrians involve male drivers. Women drivers are simply better.