At Nissan and GM the wheels of progress roll relentlessly faster. These two automakers are leading the industry's push toward fully self-driving vehicles.

And these are vehicles that you and I might buy one day; much sooner than any of us may have thought. These are vehicles that are actually intended for use on real city streets and highways; not remote test centers in the Mojave Desert.

Nissan officials said just weeks ago that it will begin selling autonomous cars by the year 2020. GM meanwhile says it's getting there too, but there are still many obstacles to cars that completely drive themselves, including how they react to cars and trucks that don't have the technology.

Nissan chief executive Carlos Ghosn said in a prepared statement: "I am committing to be ready to introduce a new ground-breaking technology, Autonomous Drive, by 2020, and we are on track to realize it."

Nissan said it is working with a number of universities, including the Massachusetts Institute of Technology, Carnegie Mellon and University of Tokyo to perfect the technology. The company is also building a special testing facility in Japan.

The automaker said it plans to have multiple self-driving models on the market in seven years and to have the technology available across its model range "within two vehicle generations." Cars are typically fully redesigned every five to six years, so that could be within 10 to 12 years.

Clearly, there are many automakers racing to be the first to launch a successful self-driving vehicle. General Motors, Toyota and Germany's Audi, part of the Volkswagen (VLKAF) Group, are also working on self-driving cars. Google has long been working on the technology for years, as well.

CNN reports that a number of cars now on the market, for example the Mercedes-Benz S-class, have features that can take partial control of a car in certain circumstances to handle tasks such as active cruise control - which automatically keeps an even space between cars in traffic, automatic braking, lane-keeping and parking. Nissan's Infiniti luxury division recently began selling the new Q50 which has some of these features as well.

As self-driving cars come closer to reality, a number of states have passed laws regarding testing of the vehicles on public roads. The National Highway Traffic Safety has also recently proposed rules for self-driving cars.

Of course until recently, engineers haven't resolved the problem of steering with computers.

"The steering control is the big additional piece," said John Capp, GM's director of electrical controls and active safety technology.

GM engineers showed off the steering system for reporters at the company's testing grounds in Milford, Mich. The system adds control of electric power steering to other technology that's now available. Although bugs remain, a Cadillac SRX SUV equipped with the steering technology worked very well, USA TODAY reported.