You can expect to see the first privately owned driverless car tooling around the neighborhood in seven years, or 10 years, or “far off in the future.”

The cars will become the popular mode for getting around in your lifetime, or your children’s lifetime, or before your grandchildren start walking.

Different timelines, yes, but everyone who testified Tuesday on Capitol Hill agreed on one point: The technology exists, and cars capable of driving themselves are in your future — sometime.

“These vehicles could potentially be on the road by the end of the decade,” said Joshua L. Schank, president of the Eno Center for Transportation. “The benefits from autonomous vehicles are substantial, but the barriers also are substantial.”

Schank joined two carmakers, a professor, a state transportation chief and the head of the National Highway Traffic Safety Administration in testimony before the House subcommittee on highways and transit.

With most domestic and foreign automakers plowing ahead with development, more of the necessary technology being installed in production-line cars each year and test models already motoring down the road, clearing the barriers Schank and others described seemed a greater challenge than making the cars.

The allure of autonomous vehicles to automakers and lawmakers — and perhaps eventually to drivers — is enormous. They have the potential to transform individual travel in the United States as profoundly as did the move from horses to cars, or from two-lane highways to the interstate system.

The upside potentially includes a large reduction in fatal accidents; 40 percent of deadly crashes involve alcohol, and autonomous vehicles don’t drink.

“It’s not a question of if, but when” autonomous cars debut, said Raj Rajkumar, a Carnegie Mellon professor. “This technology will basically prevent human beings from hurting themselves.”

Accidents of all sorts cause congestion, so fewer accidents would mean less congestion. Computer controllers and linked vehicles could keep everyone moving at speed most of the time, reducing traffic tie-ups even more. People with disabilities, the elderly and the young would have greater mobility. After dropping off passengers, cars could park themselves or drive home on autopilot.

But before they hit the market, there are those barriers.

Three listed by Tuesday’s witnesses were the cost (perhaps $100,000 early on), privacy concerns and potential hacking of the systems by terrorists, and liability protections for automakers if computer-driven vehicles crash.

“So we’re not forced to first go to Europe or China where we have a better [legal] environment,” Michael J. Robinson, a General Motors vice president, told the subcommittee. “We are the most litigated industry you can find. It shouldn’t shock anyone that we think about that when we consider deployment.”

Robinson said that while GM is moving “full speed ahead” with technology, “these kinds of driverless systems are a significant distance in the future.”

NHTSA Administrator David L. Strickland agreed, saying, “We see a fully autonomous vehicle being far off in the future.”

But Andrew Christensen of Nissan said his boss wants to have them on the road by 2020.

Whenever they arrive, it will be an additional 10 years before they make up a significant percentage of the vehicles on the road; normally it takes 20 years before there is a complete turnover of cars.

Lawmakers’ reactions ranged from technical cross-examination to bemusement. Rep. Dina Titus (D-Nev.), whose state already regulates autonomous vehicles, said, “While many of my colleagues are amazed or titillated, the state of Nevada is on top of this.”

Albio Sires (D-N.J.) wondered how driverless cars would negotiate New York City. “It’s the future. I get it,” he said. “It’s just scary.”

Rep. Roger Williams (R-Tex.), a car dealer, worried about whether the vehicles would have enough power to pull a horse trailer.“It’s got to have some towing capability,” he said.

Del. Eleanor Holmes Norton (D-D.C.) was assured by GM’s Robinson that “the cost will come down over time if it’s a system that people value.”

“I have yet to have a car drive me,” Norton said. “I’m looking forward to that.”