Self-driving Uber vehicles are back on the road in Pittsburgh, Pennsylvania - but with a human driver on duty behind the wheel. File photo: Eric Risberg / AP

Pittsburgh, Pennsylvania - Uber is taking the first step toward restarting its autonomous ridesharing program, putting its self-driving cars back on the road in 'manual mode', with a driver at the wheel at all times.

The ridesharing giant said on Tuesday its specially equipped vehicles would be back in service for the first time since it suspended tests following a fatal accident in Arizona.

"We're starting with cars in manual mode," it said, "with a mission specialist sitting behind the wheel and manually controlling the vehicle at all times. While we are eager to resume testing of our self-driving system, we see manual driving as an important first step in piloting these safeguards."

The testing will enable Uber to gather data on different scenarios that will be recreated in computer simulations, and also develop more accurate mapping for the vehicles.

Pedestrian killed

Uber suspended its autonomous driving testing in several locations in the United States after the March accident in Arizona that killed a pedestrian. The National Transportation Safety Board said in a preliminary report in May that the car's sensors detected the pedestrian six seconds ahead of the crash but failed to activate emergency braking.

The NTSB said Uber's engineers had disabled an automatic emergency braking system "to reduce the potential for erratic vehicle behavior." The pedestrian was dressed in dark clothing and was pushing a bicycle that had no side reflectors when she crossed a unlighted section of roadway.

Uber said that in the new tests in Pittsburgh, the self-driving vehicles will have a driver-monitoring system "to help ensure mission specialists are remaining attentive behind the wheel". The system will send an audible alert if it detects driver inattention. The vehicles' automated collision avoidance systems will remain enabled during manual driving - activating emergency braking when they detect a potential accident.

Agence France-Presse