It has been a futurist fever dream since at least 1939, when visitors to the General Motors pavilion at the New York World's Fair marveled at a glimpse of the automotive future: a miniaturized model of a city prowled by 50,000 robot cars, controlled not by drivers but by centralized radio waves.

That future may have been delayed a bit (the GM pavilion boldly predicted that people would be out from behind the steering wheel by 1960), but it's no longer pulpish science fiction: Several car companies say they'll begin selling vehicles that can drive themselves — at least part of the time — by the end of this decade. And Florida will be ground zero of the automotive revolution.

"We want to be the state that's ready for innovation," says Ananth Prasad, Florida's transportation secretary. "We want to be the state where entrepreneurs and great minds can come to try things, rather than the state that just says no."

One of just four states that permit experimental driverless vehicles to be driven on public roads, Florida has been the site of tests to see how their crash-averting sensors react to sudden and vicious thunderstorms. A section of Interstate 4 between Orlando and Tampa already has been equipped with transponders that feed the cars information about traffic and road conditions.

And when auto manufacturers and government officials from across the country held a summit last year to work out some of the legal and technological issues surrounding the vehicles, they chose Tampa to host it.

During a car show accompanying the summit, Prasad took one of the prototypes out for a spin. Or, maybe, it took him.

"It felt a little odd, sitting there with my hands away from the wheel, on an interstate with people going by me at 70 miles an hour," he recalls. "But it wasn't scary or intimidating. Of course, obviously I was in a car full of Google engineers if anything went wrong."

Google, the Internet company that has been testing Priuses and Lexuses festooned with radar, lasers and video cameras that allow the vehicles to be driven by their software rather than humans, says it expects its "autonomous driving system" to be on the road by 2018.

Several car manufacturers are only slightly less optimistic. Nissan, Mercedes-Benz and Renault all have announced plans to market cars in 2020 that can drive themselves at least part of the time.

"A lot of people question whether we're going to see this in our lifetime," Prasad says. "I think they're going to be very, very surprised. … Autonomous vehicles are much, much closer than we think."

In fact, they're already here — kind of. Several of the key technologies in creating a full-blown driverless car already have been deployed. Some Mercedes models sold in Europe can be put on autopilot in low-speed traffic jams; taking cues from the vehicles ahead of them, they stop or go, speed up or slow down as traffic permits, while keeping themselves inside the lane.

Volvo equips some cars with a pedestrian-protection system that hits the brakes hard if the car's radar spots a person in the street ahead.

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Surely, many of the 31,000 Americans who die in traffic accidents each year would be saved if drivers and their unfortunate tendencies to drink beer, send texts, apply makeup and race trains were taken out from behind the wheel — not to mention the elimination of things like fog-bound pileups and collisions due to rearview mirror blind spots.

"That death toll — it's like having an airliner crash every day of the year," says Paul Feenstra, senior vice president of the Intelligent Transportation Society of America. "If that were to happen, we'd have congressional hearings every day to get to the bottom of it. But it's become an acceptable norm on the nation's highways, and it doesn't have to be."

The quixotic dreams of urban planners for vast tracts of parkland and bike paths and playgrounds might become affordable if cities could get rid of all their parking lots. And, maybe, they could.

"You probably don't need parking garages anymore once you have driverless cars," says Chandra Bhat, director of the Center for Transportation Research at the University of Texas. "You'd just call an autonomous taxi to pick you up in the morning and return you in the afternoon. Somewhere from 20 to 80 percent of urban land area could be repurposed."

Some theorists think the entire foundation of private car ownership will be shattered. "There's a lot of talk about people joining fleets or clubs, like Netflix for cars, where you'd just order one up when you needed it," says Loren Smith, an analyst who follows government automotive policy for the research firm Capital Alpha. "You wouldn't have a car sitting in the driveway for 23 hours a day, doing nothing."

The productivity of American workers would soar as commute times shrink — traffic jams would be a thing of the past as computers mass driverless cars into perfectly spaced convoys traveling at uniform speeds — and workers can spend the time working on their laptops instead of trying to cut in front of the guy in the next lane.

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Google thrilled the industry a couple of years ago with a video of a blind man in the driver's seat of one of its automated cars as it carried him first to a fast-food restaurant and then to pick up his dry cleaning. Driverless cars promise new independence to disabled people and — not inconsequential in a country where the massive baby boom generation is passing into retirement — senior citizens whose driving skills have waned.

Whatever its potential benefits, the road to a driverless car horizon is filled with legal, political and social potholes.

One of the biggest: liability law. No matter how good the technology is, there are going to be accidents, especially with a mix of human drivers and robots, which will be the situation for decades as the new cars penetrate the market. It can be something as simple as a tire blowout or as complicated as a power surge that knocks out some of the technology while the driver is asleep and can't take over. Lawyers and insurance companies will be watching carefully and looking at the question of who is responsible.

Technology failures might not be just legally complicated, but terrifying: What if a virus or a hacker invaded the software of vehicles and sent them reeling out of control? What if terrorists start using driverless cars to deliver suicide bombs that don't require suicides?

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Infrastructure is another problem that may take years to overcome. No one has even ventured a guess as to how much it will cost to embed America's 8 million lane-miles of roads with the network of transponders and sensors necessary to relay road and weather conditions to vehicles.

Privacy issues associated with driverless cars may prove nettlesome. The technology in a driverless car will record exactly where it has been and when, information that the owner might not want to have available to a nosy government agency or a truculent divorce lawyer.

Then there are potential corporate commercial clashes with privacy, too. What if Google, which knows you have a weakness for Big Macs because of information it has collected from your Web browsing, strikes a deal and instead of mapping your driverless car on the shortest route to the office sends it to one that takes it past a McDonald's?

"The privacy people are going to go crazy when they figure out all the implications of this stuff," predicts Robert Poole, editor of the industry newsletter Surface Transportation Innovations. "It's massive data collection, the GPS big-brother box in the car."

Poole, though a fervent supporter of driverless-car technology, thinks there's "a lot of mindless optimism" among its backers. He thinks its adoption will take much longer than anyone expects, and fall considerably short of the complete overhaul of society that they hope for.

"You just aren't going to see blind people traveling alone in these cars on freeways, or traffic jams disappear, or cities completely re-engineer themselves," he says. "As strong a technology as it is, things break and stuff goes wrong, and there will always have to be a human driver sitting there, ready to take control."