The visionary world where cars will travel about without drivers will be shaped by a third set of federal guidelines this summer, one that seeks to nudge the nascent industry rather than regulate it.

“We are not going to be selecting what [technology] should be used,” Derek Kan, undersecretary for transportation policy said. “We’re looking at ways to evaluate outcomes. Instead of a regulation that says, ‘Machine must have A, B and C in a vehicle’, we hope to look at how safe a vehicle is at the other end.”

Kan spoke Thursday at what the Department of Transportation billed as a “listening session” for automakers, tech companies and state officials.

The federal government finds itself in a balancing act, trying to avoid onerous regulations that might inhibit an emerging technology while ensuring a safe transition to a game-changing future.

Transportation Secretary Elaine L. Chao acknowledged the tightrope in remarks at the event.

“The department is holding this summit and taking other steps to gather information as we move forward on the regulatory front,” Chao said.

She also pointed out that a recent AAA survey found 63 percent of Americans said they were afraid to ride in a fully autonomous car.

“That’s down from 78 percent reporting such fears in early 2017, but it’s still a pretty big number,” Chao said.

All that will change in relatively short order, said Steven G. Bradbury, general counsel at DOT, who pointed to the transition from horse travel to the first autos early in the 20th century.

“Once consumers became convinced that this dangerous new unknown technology was safe and was productive and was useful, everything changed and consumers went for motorcars like crazy,” Bradbury said.

He predicted that autonomous vehicles were “coming really fast” and that regulators may need to catch up once the cars have debuted, or adapt existing regulations to driverless cars.

“We don’t want to have to reinvent the wheel and start from the ground up and rewrite all of our regulations if we don’t have to,” Bradbury said.

Twice, in the latter days of the Obama administration and again last year, the Department of Transportation has laid out in an advisory framework its vision for autonomous vehicles.

The most recent iteration, released in September, contains the phrase “voluntary guidance” five times in its first five paragraphs.

“We are not in the business — we don’t know how — to pick the best technology,” Chao said. “We’re not in the business of picking winners and losers. The market will decide.”

The delicate issue of how best to handle the impending advent of autonomous vehicles has been a challenge for federal regulators, state authorities and automakers.

The traditional divide between federal and state governments has been relatively simple. On the federal side, authorities could dictate national safety standards — sometimes by threatening to withdraw federal highway funding — and issue model recalls if they found flaws in safety features, like Takata’s exploding air bags or Ford’s 2005 cruise control problems with pickup trucks and SUVs.

The states issued driver’s licenses and regulated driver behavior by setting speed limits, enforcing drug and alcohol limits, and myriad other driver limits.

“What happens when some of those operations are now done by a computer?” Kan said. “Is that the role of the federal or state government? We hope to clarify some of these questions.”

In future decades, as driverless cars become more dominant, the role of the states may shrink and that of the federal side may grow. More immediately, however, states are being asked to allow autonomous test vehicles to use their roadways and have appealed to Washington for guidance.

“The department will work with the states to avoid a patchwork approach [of state laws] that could inhibit innovation,” Chao said.

California is one of several states that have allowed the vehicles, granting 50 companies the right to test them on public roads.

The other looming question is whether, or to what degree, federal regulators should set standards for autonomous cars before their rubber hits the road. Despite numerous exceptions — seat belts, back up cameras, and eye-level brake lights — the federal government has focused more on recalling the bad than dictating what comes off the auto assembly line.

“Literally, we’re bringing science fiction into reality,” Kan said. “We must ensure that the policy we set, the ground rules, the frameworks, enable all of these technologies.”