Congressional Republicans and Democrats in Washington drew battle lines Tuesday over a package of self-driving vehicle bills that would pre-empt state-level regulations, including those in the final stages of development in California.

U.S. House Republicans have unveiled 14 draft bills that seek to expand the federal government's role in setting rules for testing, developing and making road-ready highly autonomous vehicles. The legislation responds to industry concerns that individual states are creating a patchwork of potentially conflicting laws to oversee the emerging industry.

“The question is, do you want these cars to stop at every state line because every state would have a different system,” said U.S. Rep. Greg Walden, R-Oregon, at a hearing of the House Digital Commerce and Consumer Protection subcommittee. “We've never done that in America with autos.”

Democrats and consumer advocates, while touting driverless cars' potential for slashing the number of road and highway fatalities, expressed skepticism of attempts to pre-empt state laws when the National Highway Transportation Safety Administration has not adopted standards for autonomous vehicle features.

“I know of no law in which Congress has attempted to preclude states from acting when neither it nor any federal agency has taken any action in that subject area,” Alan Morrison, the associate dean for public interest and public service law at George Washington University Law School, told the committee.

“There will always be questions about how much overlap there is between what the federal government has done and what the state wants to do, but that always assumes some federal action to support pre-emption,” Morrison said.

The Obama administration in September rolled out broad guidance for the driverless-car industry, laying out a prominent role for federal regulators to oversee testing, development and operations for the vehicles. President Donald Trump, however, has emphasized deregulation in many government sectors and in February new Transportation Secretary Elaine Chao said the policy was subject to change.

In the absence of any additional federal action, states have taken different approaches. California regulators held the final public hearing in April in what has been a years-long process of adopting rules for operating the vehicles on public roads.

“The DMV received a lot of helpful public input during the 45-day comment period,” a DMV spokesperson said. “We're currently going through all of that and still working toward having the regulations finalized by the end of the year.”