Pittsburgh, your self-driving Uber has arrived.

Autonomous Ubers will start picking up passengers today in Steel City, though a "driver" will be along for the ride in case of emergency. "If a self-driving Uber is available, we'll send it along with a safety driver up front to make sure the ride goes smoothly," the company wrote in a blog post. "Otherwise it's uberX as usual."

In early 2015, the ride-hailing app teamed up with Carnegie Mellon University to create a center in Pittsburgh where it could research and develop autonomous technology. A year later, Uber confirmed trials of a driverless automobile, suggesting that "real-world testing is critical to our efforts to develop self-driving technology." Last month, it tipped self-driving taxis in Pittsburgh "soon."

Now, a fleet of hybrid Ford Fusions are roaming the streets, branded with Uber's Advanced Technologies Center (ATC) logo and outfitted with an array of sensors.

According to CEO Travis Kalanick and VP of self-driving tech Anthony Levandowski, an autonomous taxi service has "enormous potential" to help reduce the number of traffic accidents, free up space in cities, and cut congestion.

"We know that many drivers will have questions about this technology," which will be on the road 24 hours a day, the pair said in the blog post. That's why a driver will be there to intervene if necessary.

For now, Uber has no plans to completely replace human drivers with autonomous tech. "People-powered transport is uniquely able to solve...the limits of self-driving software and the skyrocketing demand for better transportation which people-powered transport is uniquely able to solve," Kalanick and Levandowski wrote. Still, Uber is investing heavily in autonomous tech. It recently parterned with Volvo and acquired Otto, a start-up "whose mission is to rethink transportation, starting with self-driving trucks."