NEW YORK (CNNMoney) -- The "driverless cars" of science fiction fame are closer to reality than you think.
But they won't arrive all at once in a single magnificent new machine. In fact, when the driverless car does come, it will happen gradually -- one new technology at a time.
Sure, Google is testing cars that can drive set routes with minimal human interaction, but they're not ready for Main Street yet. (Google (GOOG, Fortune 500) was not available for comment on this story.)
The first "autonomous driving" systems will only take full control in certain environments, such as interstate highways.
Self-driving cars aren't just a matter of convenience; safety is the driving force. That's why some people are pushing for a faster roll-out of the technology, said Bryant Walker Smith, a fellow at Stanford Law School who has written extensively about self-driving cars.
Over 30,000 people a year are killed in car crashes, the majority of which are caused by human error. Computers may not be perfect, but they're almost certain to be far better than us.
"How long are we willing to wait and let people die before we move to the autonomous car?" said Smith.
Semi-autonomous driving has already started with "active safety" features. They take over only some of the driving, especially during emergency maneuvers or when drivers are tired.
"We and other automakers have been adding active safety features gradually," said Nady Boules, director of electronics and controls for General Motors (GM, Fortune 500).
Boules headed the team that created "The Boss," a self-driving Chevrolet Tahoe SUV that won a Defense Department-sponsored contest for self-driving cars in 2007.
Each of these new features not only makes cars safer but points out ways in which computers can be better at driving than we are:
Electronic stability control: This technology helps drivers keep cars from skidding during abrupt maneuvers.
Pre-collision warning systems: They detect an imminent crash and prepare the brakes.
Active cruise control: It uses radar to detect cars ahead and automatically slows the vehicle to maintain a safe following distance. Most of these systems work only at speeds above about 30 miles an hour. Some more advanced systems -- including ones from Mercedes-Benz and Nissan's Infiniti -- work at any speed, even in stop-and-go traffic.
Pedestrian detection: Volvo has a system that scans ahead looking for pedestrians who seem to be moving into the path of the vehicle. The system can even apply the brakes if someone steps in front of the vehicle.
Autonomous steering: Some vehicles, particularly ones from Infiniti, have systems that recognize lane drift and gently nudge the steering wheel to help guide the car back into the center of the lane.
Several new Ford (F, Fortune 500) cars can now even parallel park themselves. The driver needs only to operate the gear selector, the gas and the brakes. All the steering wheel movements happen on their own, guided by a sensor that has already measured the size of the parking space.
Vehicle-to-vehicle communication: A major cause of crashes today is simple miscommunication. Drivers have limited options for letting others know what they're about to do.
"The ways I communicate with other cars are my horn, my lights and my middle finger," said Smith.
In the age of wireless networks, we can do better. It would be fairly easy for every car to electronically broadcast its speed, braking and steering inputs to cars around it so that all the cars in a given area would know what every other car was doing. Cars could then react to each other automatically.
V2V communications, as it's called for short, is actively being pursued by a consortium of major automakers, and experimental cars are already in use. The National Highway Traffic Safety Administration is expected to rule next year on how to move forward with this technology.
On Tuesday, Consumer Reports magazine announced its strong support for the technology, which could save thousands of lives even in human-driven cars.
So what happens now? Once these systems learn to handle the easy stuff such as highways, the next step will be complex city and suburban roads with intersections and pedestrian traffic.
At first, automated driving will be entirely voluntary and used only depending on the situation and your comfort level.
"For the near term, there will always be a driver in the seat and, always, the driver will be responsible," said Boules.
As these systems get better, though, you will begin to phase yourself out more and more, until, finally, you give up control for good. 
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