Uber just announced that it has begun a pilot program of driverless cars in Pittsburgh. The cars still have engineers riding along who can take care of problems as they arise, but its ultimate goal is to provide cars that simply don’t have human drivers.

Uber maintains that this day is still well down the road, and that the technology of drivrless cars still has some bugs to be worked out. However, even during peak ride sharing hours, the company doesn’t expect this program to replace human drivers but to supplement them.

“Even when these technology issues are fixed, we believe ride-sharing will be a mix—with rides provided by drivers and Self-Driving Ubers,” says an Uber spokesperson.

The Independent Drivers Guild of New York City, which represents 35,000 Uber drivers there, has already vowed to take a stand against driverless cars. Such vehicles are currently illegal in the city, and they will be “aggressively fighting” to keep these laws in place.

This comes as no surprise, since quite a few people around the country rely on ride-sharing jobs—driving for companies like Uber and Lyft—for some or all of their income. The idea of being replaced by automation can’t be a reassuring one.

If Uber does implement driverless cars, it would probably be the fastest that a technology shift has ever happened, since the whole ride-sharing industry is barely five years old.

Uber has claimed that drivers can switch over to maintaining cars, but this is largely seen as unrealistic.

“I don’t think many Uber drivers, as they are kicked out of driving for Uber, will want to go maintain those cars,” says Harry Campbell, a ride-share industry blogger and part-time driver for Uber and Lyft.

Uber has made no secret of its goals to introduce automated cars and to even eliminate car ownership in the future, and drivers have reason to be concerned. A great deal of the U.S. economy revolves around service jobs, from waiting tables to retail to ride-sharing gigs. When we start to replace these jobs with automation, there could be unintended economic and social consequences.