Four driver-less electric vehicles have completed a four-month 15,000 km trip, as part of a research project conducted by the University of Parma in Italy.

The university said it was the longest test to date for vehicles without a driver at the wheel.

The university’s Vislab autonomous driving laboratory conducted the experiment to test how vehicles without human drivers would perform under extreme conditions. The four vehicles drove from Parma to Shanghai.

The test cars were equipped with seven cameras, four laserscanners, GPS and onboard computers. The electric vehicles’ autonomous piloting systems were powerd by solar cells.

Among features tested on the trip were stop-and-go, following the car in front, obstacle detection and terrain slope estimation and mapping.

Vislab said that human intervention was required in some situations where the computers did not provide satisfactory results. However, “the work to adapt the system to those occasional situations has already begun,” Vislab said.

New and improved technologies are raising prospects that driverless driving will happen sooner than many had thought. Google has been making test drives with a driverless Toyota Prius. And other companies are experimenting as well.

Proponents of driver-less driving believe it will help reduce accidents. Making better use of telematics and navigation systems could also cut congestion on the roads and lower car emissions.