A self-driving shuttle bus goes for a test drive in Finland in August. (Ville Mannikko/Bloomberg)

Federal highway safety regulators are gently rebuking a California plan that would compel automakers to show how they are addressing privacy, safety and a host of other questions about their self-driving cars — a novel technology that could transform the U.S. transportation system.

The plan from California's Department of Motor Vehicles would make it mandatory for manufacturers to complete a 15-point report on safety and other issues before testing automated vehicles or allowing them on public roads. It has been criticized by the automotive industry as being overly burdensome and a threat to innovation.

The idea for the report came from a set of guidelines from the National Highway Transportation Safety Administration that was released in September. But the suggestions were never meant to be mandatory or prescriptive, NHTSA Administrator Mark Rosekind told members of Congress in a committee hearing Tuesday. Asked specifically about the California proposal, Rosekind said it would make little sense for self-driving technology to have to obey different rules for each state.

"Everyone wants to see a consistent national framework," Rosekind said. "Just think if an autonomous, self-driving car stopped at every state line [because it didn't meet state regulations]. Everyone wants to avoid that patchwork."

The submissions NHTSA has requested of the industry are voluntary. Companies such as Google, Uber and Tesla are testing new, groundbreaking automotive capabilities. By embedding sensors and communications arrays in the vehicles, companies are allowing cars to make turns, change lanes and stop for pedestrians without the need for a driver.

Until this fall, only a handful of states — including California — had any rules in place for the testing of autonomous vehicles. That policy vacuum has led some in the industry to seek out partnerships with cities, such as Pittsburgh. This fall, Uber rolled out a pilot project for self-driving cars in Pittsburgh that allows members of the public to hail a driverless Uber downtown.

Pittsburgh was hailed by Uber officials as a "double black diamond" for testing in terms of the city's hilly terrain and older city streets.

On a mass scale, how self-driving cars will function in inclement weather, poor road visibility and other tough conditions remains a major question, said Rep. Jan Schakowsky (D-Ill.), and consumers should not necessarily give automakers the benefit of the doubt after the industry's recent spate of recalls and emissions scandals.

"The automotive industry doesn't always have a great track record with consumer trust," Schakowsky said. "If the industry says to trust us with autonomous vehicles, why should consumers take them at their word?"

Self-driving cars will not be adopted quickly if the public does not trust the technology — meaning that automakers have an incentive to be open with consumers about safety, Rosekind said. "If you want everyone to trust what you're working on, we think you would want the most transparent, thorough public notice on what you're doing to address safety up front," he said.

Proponents of self-driving cars say the technology has the potential to save lives, lower insurance costs, reduce congestion and road emissions and alter America's approach to land use. More than 35,000 Americans were killed on public roads last year, according to federal statistics, and 94 percent of all car crashes are the result of human error. By making better decisions, policymakers say, robotic cars can dramatically change the way we get around.