Uber’s autonomous prototypes have returned to the streets some nine months after a fatal crash involving a pedestrian in March.

In a Medium post, head of Uber Advanced Technologies Group Eric Meyhofer, revealed that the technology company has implemented a series of changes to improve the safety of its self-driving vehicles.

As reported by The New York Times, Uber recently received permission from the Pennsylvania Department of Transportation to recommence testing of its vehicles on public roads in Pittsburgh. However, the vehicles will only operate on a small section in Pittsburgh’s Strip District and only during daylight hours on weekdays.

In addition, each Uber prototype will have two drivers inside at all times, operating in four-hour shifts, significantly less than the eight to 10 hour shifts previously in place. The vehicles will also be restricted to a maximum of 25 mph (40 km/h), down from the 55 mph (88 km/h) they were previously capable of reaching.

“We will continue to prioritize safety and proactively communicate our progress until we’ve built a self-driving system that lives up to the promise of making transportation safer and more affordable for everyone,” Meyhofer said.

Uber will also resume testing of autonomous vehicles in San Francisco and Toronto but the cars will not operate autonomously and will be driven by a human at all times.

Uber paused public testing of its self-driving vehicles when a bicyclist in Arizona was struck and killed by a prototype. Investigations found that the Volvo used by Uber detected the pedestrian 1.3 seconds before the collision but failed to brake. The human operator was also found to have been streaming The Voice at the time of the crash.