Automakers, suppliers and technology companies that want to test autonomous vehicles on California roads may have to pony up for a $5 million insurance policy.

The requirement, intended to cover the potential costs of a self-driving car going haywire, is one of the key provisions of a regulation that California officials proposed last month to minimize the risks of letting car companies and Silicon Valley tech developers such as Google Inc. put the experimental vehicles on public roads.

The proposal, released Nov. 29, is a sign of how autonomous driving, once the province of engineering students and hobbyists, has caught the government's eye. State by state, the technology is falling subject to certification, training and reporting requirements that will effectively limit road testing to large, sophisticated outfits.

"California is leading the way in autonomous vehicles, and these testing regulations are the first step in making the technology available," said Bernard Soriano, deputy director of the California Department of Motor Vehicles and leader of the DMV's self-driving-vehicle program.

The DMV says it will take comment on the proposal until mid-January and release final regulations as early as next spring.

Autonomous vehicles are widely allowed across the United States, although they tend to fall outside the contours of the law. State licensing rules don't apply to vehicles that act as their own drivers.

Some companies have called for state laws and standards to explicitly authorize self-driving cars, knowing they could be taken to court for far more than $5 million should something go wrong on the road.

Among the proponents of state laws is Google, which says it has logged more than 500,000 miles of autonomous driving using its fleet of modified Toyota Prius hybrids.

But some automakers argue that state laws are stifling and premature. Michael Robinson, vice president of sustainability and global regulatory affairs at General Motors, said last month during a congressional hearing that the automaker wants one set of federal rules, "not a patchwork of various state attempts to become involved."

The National Highway Traffic Safety Administration has released guidance for states crafting laws, but has not issued any regulations.

California, Nevada, Florida and the District of Columbia have passed laws allowing self-driving cars to be tested within their borders. California would be the second state to subsequently put out regulations covering the testing. Nevada finalized its rules last year.