The new United States policy on self-driving cars received a mixed reaction from highway-safety advocates, who acknowledged the technology's life-saving potential though they warned of a world of "human guinea pigs".
The Transportation Department's new guidelines give carmakers and states "the green light to innovate while keeping safety at the forefront," said Ms Deborah Hersman, president and chief executive officer of the National Safety Council, an Itasca, Illinois-based non-profit organisation that seeks to reduce injuries and deaths on the road.
At the same time, there is a danger that untested technology will be foisted on unwitting consumers, said Ms Jackie Gillan, president of the Washington-based Advocates for Highway and Auto Safety, an alliance that includes consumer, medical and safety groups, along with insurance companies.
Regulators must continue to exert strong oversight, with minimum performance requirements, rigorous testing and verified data, she said.
"Consumers cannot be 'human guinea pigs' in this experiment and the federal government cannot be a passive spectator," she said.
The Obama administration's voluntary guidelines for self-driving cars, formally unveiled on Tuesday, include 15 benchmarks carmakers will need to meet before their autonomous vehicles can hit the road.
Carmakers are being given freedom to come up with their own ways of making self-driving cars safe in each category, but they are being asked to explain them in detail before putting them on the road.
The carmakers will have to show how their virtual drivers will function, what happens if they fail and how they have been tested.
Companies developing the cars - such as Tesla Motors, General Motors and Google parent Alphabet - must make vehicle performance assessments public, so regulators and other companies can evaluate them.
"There has never been a moment like this, a moment where we can build a new culture of safety as a new transportation technology emerges that has the potential to save even more lives, and one that enhances the lives of so many Americans," transportation secretary Anthony Foxx said.
The new federal policy builds on a philosophy of "proactive safety" at the National Highway Traffic Safety Administration (NHTSA), he said.
Building on models that have made aviation safer, the NHTSA would find ways for companies to share information, so that best practices spread quickly throughout the industry, he said.
Ms Colleen Sheehey-Church, national president, Mothers Against Drunk Drivers (MADD), said self-driving cars have the potential to greatly reduce the more than 10,000 fatalities a year caused by drunk driving.
"A self-driving car can't get drunk," she said. "A self-driving car can't get distracted. And a self-driving car will follow the traffic laws and prioritise safety for pedestrians and bicyclists."
Other safety advocates responded cautiously.
"The manufacturers always complain about new federal protections, but autonomous cars are a whole new technology with great promise but also with the potential for serious public harm," said Ms Joan Claybrook, a former administrator of the NHTSA and a leading consumer advocate.
NHTSA's voluntary agreement rolling out automatic emergency braking on most vehicles for sale in the US is "useless", she said, because a fatal Tesla crash in May showed that the technology does not always work.
In that incident, a Tesla Model S was being driven by the car's "autopilot" system. The car failed to distinguish between a white truck blocking the road and the brightly lit sky and the driver was killed.
The new guidelines include recommendations for states to pass legislation on introducing self-driving cars safely on their highways.
It says states should continue to license human drivers, enforce traffic laws, inspect vehicles for safety and regulate insurance and liability.
The federal government, it said, should set standards for equipment, including the computers that could potentially take over the driving function.
It will also continue to investigate safety defect and enforce recalls.
President Barack Obama wrote an op-ed in the Pittsburgh Post-Gazette saying automated vehicles have the potential to dramatically reduce the number of people who die on the roads.
"If a self-driving car isn't safe, we have the authority to pull it off the road," Mr Obama wrote. "We won't hesitate to protect the American public's safety."
Portions of the proposed guidelines will be effective immediately. Other elements will go into effect after public comments are received and analysed. The government said it will update its self-driving car guidelines annually.
Mr Mark Rosekind, the NHTSA's administrator, has said the self-driving car plan would be key to the agency's attempts to reduce human error, which the agency estimates is a factor in 94 per cent of fatal car crashes, which killed more than 35,000 people in the US last year.
The new policy provides a path for going fully driverless by removing the requirement that a human serve as a backup, the US' Transportation Department officials said.
Under the new set of guidelines, carmakers will be deciding for themselves how to meet each of the 15 safety tests.
They will then document their evidence for the NHTSA. They will be providing a lot more information up front than manufacturers of traditional cars, which only have to certify that their models meet minimal federal safety standards.
The development is important because some state regulators, including those in California, have proposed that humans must be ready to take over in robot cars at a moment's notice.
Google's self-driving car project and others have objected, saying that limitation could stifle development of the technology because it would require robot rides to have steering wheels, gas and brake pedals, at least in the test phase.