Cars will drive themselves in three phases: First, traffic jams

That's according to Carlos Ghosn, Chairman and CEO of auto makers Nissan and Renault, who told a Mobile World Congress audience on Monday that self-driving cars will come in three phases. Nissan is working with U.S. space agency NASA on autonomous car technology.

Phase One will help you out when you probably least enjoy driving: In traffic jams. Starting next year, Nissan and Renault will make cars that can drive themselves in stop-and-go highway traffic, Ghosn said. The technology's ready for this, so all that's left is for governments to allow it, he said.

The next phase, coming in 2018, will see cars that can drive themselves on a highway at normal speeds and can even change lanes.

City driving won't come until the third phase, in 2020. It's a much bigger challenge because there are so many different objects around that cars have to see and respond to appropriately, Ghosn said. There are some tough decisions, too. For example, a self-driving car in the city would have to decide what to do if it's stopped at a red light and another car comes up too fast behind it: Go through the intersection or get hit from behind

A car with no driver is an even steeper technical challenge and also raises the issue of cybersecurity. Regulators will be much more reluctant to allow driverless cars than vehicles that do the work but have a human behind the wheel, Ghosn said.

Like any technology, self-driving features will start out expensive and gradually get cheaper. Each phase of self-driving technology will first come available in high-end vehicles and then work its way down to mass-market models, Ghosn said.

Nissan and NASA teamed up because each had something to offer the other, he said. NASA contributes its knowledge of robotics and human-machine interfaces, and Nissan is helping NASA research driving on Mars. The agency wants remote-control rovers that can deal with more obstacles on their own so they can cover more ground, Ghosn said.

Stephen Lawson covers mobile, storage and networking technologies for The IDG News Service. Follow Stephen on Twitter at @sdlawsonmedia. Stephen's e-mail address is stephen_lawson@idg.com