WASHINGTON  — They seem right out of a Hollywood fantasy, and they are: Cars that drive themselves have appeared in movies like “I, Robot” and the television show “Knight Rider.”

Now, two years after Google invented one, automated cars could be on their way to a freeway near you. In the U.S., California and other states are rewriting the rules of the road to make way for driverless cars. Just one problem: What happens to the millions of people who make a living driving cars and trucks — jobs that always have seemed sheltered from the onslaught of technology?

“All those jobs are going to disappear in the next 25 years,” predicts Moshe Vardi, a computer scientist at Rice University in Houston. “Driving by people will look quaint; it will look like a horse and buggy.”

If automation can unseat bus drivers, urban deliverymen, long-haul truckers, even cabbies, is any job safe?

Vardi poses an equally scary question: “Are we prepared for an economy in which 50 percent of people aren’t working?”

An Associated Press analysis of employment data from 20 countries found that millions of midskill, midpay jobs already have disappeared over the past five years, and they are the jobs that form the backbone of the middle class in developed countries.

That experience has left a growing number of technologists and economists wondering what lies ahead. Will middle-class jobs return when the global economy recovers, or are they lost forever because of the advance of technology? To understand their arguments, it helps to understand the past.

Every time a transformative invention took hold over the past two centuries — whether the steamboat in the 1820s or the locomotive in the 1850s or the telegraph or the telephone — businesses would disappear and workers would lose jobs. But new businesses would emerge that employed even more.

“What has always been true is that technology has destroyed jobs but also always created jobs,” says Nobel Prize-winning economist Joseph Stiglitz of Columbia University. “You know the old story we tell about (how) the car destroyed blacksmiths and created the auto industry.”

The astounding capabilities of computer technology are forcing some mainstream economists to rethink the conventional wisdom about the economic benefits of technology, however. For the first time, we are seeing machines that can think — or something close to it.

So the rise of computer technology poses a threat that previous generations of machines didn’t: The old machines replaced human brawn but created jobs that required human brains. The new machines threaten both.

ATMs dislodged bank tellers. Microsoft Outlook manages what secretaries used to do. Expedia is replacing travel agents. E-ZPass is doing away with toll-booth operators. And robots continue to supplant factory workers.

• Associated Press