as a woman i know from me and my friends that many cab drivers from third world nations are used to treating women as chattle. have flashed, sexually abused, hit, pulled hair, and verbally abused their women passengers. they often take off in the opposite direction that a woman asks and to very desolate areas. i have gotten out of a cab far from my destination (even while pregnant), just to ensure my safety from a cab driver that i realize has no intent to take me where i'm going.
when you have a system that allows illegal immigrants who are possibly criminal from other countries to be in charge of the safety and well-being of their passenger, that is a recipe for disaster. the gps is one way to protect the city's liability, but it isn't all they should do.