Why can't my car drive itself?

I'm quite serious about this. I know the simple answer is that none of the major automobile companies have found a way to do this cost-effectively. Business Week thinks it's 20 years away. But I think they ought to be getting close by now.

Don't get me wrong. I love driving. I particularly love driving fast on a mostly empty highway. But ever since starting my new job, in which I commute an hour or more each way every working day, I find myself wishing I could do something more productive during that time. Before you say, "take public transit," let me add, "I would if I could." There is no public transit between locations in rural Tennessee.

So I seriously wish that I could tell my car where I want to go (this could be done using GPS navigation systems), then sit back and read or eat breakfast or answer emails while the car drives. Theoretically, all the necessary technologies have been developed. They would just need to be connected in one vehicle.

As I previously stated, GPS navigation systems could know where the car is located, where it is going, and how to get there. They are even sophistocated enough to adjust the route midway along if a problem comes up. We already have cruise-control systems to regulate the speed of the car upward automatically. Surely, GPS navigation systems already include information about speed limits in order to calculate the fastest routes. A car's computer could combine this information with the cruise control feature to automatically keep the car at the posted speed limit for any given stretch of road.

Lexus has created a car that can parallel park itself. In order to do this, the car must be able to control the steering wheel, so a mechanism for the car's computer to control the steering wheel has already been invented.

Lane departure warning systems have been in use on commercial trucks since 2000 and are now available in luxury cars. Put this together with the car's ability to steer by computer, and you get a car that can stay in the lane without any input from the driver at all.

Mercedes has incorporated an automatic braking system to prevent its cars from colliding when the car in front stops. And Toyota has used the same technology to allow the car for stop itself when it approaches a stop sign.

So, technology already exists to control the car's speed, to map destinations, to steer the car, to recognize lanes on the road, and to brake when necessary. If we just put all these features together in one vehicle along with a sophistocated computer and programming to use all the input and control the vehicle, we could all be riding in cars that drive themselves.

Lest you wonder about the safety of all this computer-controlled equipment, recall that airplanes are flown almost entirely by computer, and that flying to your destination is more than 100 times safer than driving there. Over 95% of accidents on highways and in airplanes are caused by human error, not mechanical or electronic problems. Face it, driving is a boring and repetitive task that requires constant concentration to perform safely; it is much better suited to a computer than to a human brain.

So I ask again, why can't I get a car that will drive itself?