The technology is almost there, but if you’re in the U.S., you may have to wait a while before you can get your hands on your very own “autonomous vehicle.”

Imagine a day when driving to work means getting behind the wheel of the car, turning your seat around and kicking up your feet to take a nap or watch the news. Using sensors that detect other cars, traffic signals and road design, a computer could drive for you and then head back home — alone — just in case someone else needs a ride.

That day is closer than you may think. Google and automakers such as Audi, Ford and Tesla are vigorously working to make that commute a reality within the decade. And the prototypes, which are now being tested on actual highways in four states and the District of Columbia, don’t look quite so futuristic: Google is testing a model that is essentially a Prius with a giant sensor attached to its roof. But companies are building anticipation for the technology and say we are just years away from having cars ready for market that will revolutionize travel, reduce traffic delays and eliminate most car accidents.

There’s just one roadblock. Before computers can start zipping us around town, an entity known for moving as fast as molasses will have to act first: Congress.

That’s because it will be up to our government to rewrite the rules of the road, particularly on safety and privacy matters, to pave the way for cars that are fully operated by nonhumans. Who is liable in a car accident? Can passengers control data about their whereabouts? What if the computer fails and no human takes over in time? And how can communication among driverless cars be protected from cyber threats?

The potential upside of driverless cars is huge. They could reduce congestion, make commutes easier, and even save lives by taking the leading cause of car accidents — human error — out of the equation. But driverless cars will also inevitably be involved in car accidents, and technical malfunctions could have disastrous consequences on the road. Sorting out who would be responsible for such an incident is one of the hairiest challenges for policymakers, and their success depends on lawmakers getting that policy right.

From a technology standpoint, it could be five years.

Not only are there few answers so far, but there isn’t even clarity on who is in charge of setting the rules — and that’s setting up the sort of Washington turf wars that are famous for grinding things to a halt.

Policymakers will need to delve into the specifics soon, given the progress automakers and companies like Google have made in advancing driverless cars. Audi spokesman Brad Stertz says his company could roll out the first iteration of driverless cars by 2019.

“From a technology standpoint, it could be five years. How the regulations evolve, what’s permitted and what’s not permitted will have a huge role in when it finally comes to market, and that’s hard to predict,” he says.

Driverless car technology is already on the roads, to an extent. Cars can self-park, brake when a driver gets too close to an object, and maintain speed in cruise control. In five years, automakers anticipate having the technology for cars that can drive themselves in low-speed, traffic situations by using sensors to detect surrounding vehicles and objects. When traffic lets up, a driver would have to take over.

Like Audi, Ford has plans to roll out driver-assisting technologies in five years, according to spokesperson Christin Baker. But major outstanding questions remain, she says, ”including what we mean by autonomous, and how we can come together to create the total transportation system infrastructure required.”

For that reason, automakers and tech companies are pressing federal policymakers to set uniform guidelines for testing and, ultimately, operating driverless cars across the country. A wide array of government officials in both the executive and legislative branches have shown interest in the issue but are only now getting up to speed on the technical details. Tangible policy responses have been limited, starting with the most basic of questions: defining what a driverless car actually is.

The National Highway Transportation Safety Administration, a division of the Department of Transportation, took an initial step in May by issuing a set of classifications for “autonomous vehicles,” as they are officially known. But with companies such as Google and Tesla heavily involved in the arena, the agency is expanding its oversight in unprecedented ways. And it is overlapping with Congressional committees that have rarely dealt with highway matters, setting up a cluster of competing interests with various groups of policymakers without much tehnical expertise in the issues at hand.

The head of the highway safety agency, David Strickland, has told Congress he is confident in his statutory authority to set rules for the cars and how other devices within the car, such as smartphones, are utilized — but he is likely to be challenged by telecom giants and other stakeholders (who’d prefer to limit the number of cooks in the kitchen) if he moves to do so.

In Congress, lawmakers are excited about the technology’s potential but proceeding cautiously. Wisconsin Republican Tom Petri, chairman of the House Transportation Highways and Transit Subcommittee, warns against the urge to set policies before the technology is ready.

“There are going to be many issues with driverless vehicles, and it’s impossible to anticipate all — or even most — of them,” he said. “Congress should try to maintain a flexible system that deals with real problems rather than a system that tries to anticipate solutions for problems that don’t exist yet.”

Sen. Claire McCaskill differs, arguing that “Congress, the Department of Transportation, and federal regulators need to get in front of this to make sure safety and privacy concerns are addressed as the technology is developed.” The Missouri Democrat heads the Senate Commerce Consumer Protection subcommittee, which oversees aspects of the highway administration and could play a key role in shaping how these cars are regulated.

As cars evolve from hunks of metal into computers on wheels, privacy matters also present a challenge for policymakers.

When Congress does eventually set the standards, it won’t just have to wrangle the rules between the 50 states but also across nations — which have been setting their own rules for testing of driverless cars, creating a patchwork of standards that has the potential to create private sector headaches.

“That’s one of the things that is going to be really challenging,” Audi’s Stertz agrees, noting that the handful of states that have allowed testing — Nevada, California, Florida and Michigan, plus Washington, D.C. — “all have different requirements.”

As cars evolve from hunks of metal into computers on wheels, privacy matters also present a challenge for policymakers. McCullough said tech companies have demonstrated their ability to protect consumers with voluntary industry guidelines and that privacy laws could slow down innovation. Of course, many believe consumers already don’t have enough control over their information — and cars driven by computers could collect an unprecedented amount of data about our whereabouts. The ACLU’s Jay Stanley called current privacy standards a “Wild West,” saying, “People’s personal information is being collected across a wide variety of sectors without their knowledge.”

That’s just another piece of the pie Congress will have to consider before driverless cars can hit the road. Citizens, for their part, seem ready. In a study released by Intel last month, 44% of Americans said they wanted to live in cities with driverless cars, buses and trains. And more than half of the survey respondents were willing to share data about their travels to make that possible.

They may start to think differently as the implications of all this evolving technology soon become more apparent. With that day fast approaching, government is going to need to hash out those issues even sooner. Washington: start your engines.