Under those guidelines, automakers and technology companies will be asked to voluntarily submit safety assessments to the U.S. Department of Transportation, but they don't have to do it.

And states are being advised to use a light regulatory hand.

At a driverless-car test track in Ann Arbor, Mich., Transportation Secretary Elaine Chao painted a near future of greater safety, fewer deaths, higher productivity and more time spent with loved ones as robots increasingly take over the tasks of driving and commuters are freed for other activities.

She unveiled a document titled "Vision for Safety 2.0" and delivered a speech that was strong on vision and light on regulation.

"More than 35,000 people perish every year in vehicle crashes," she said — 94% of those through driver error. After years of decline, fatalities are growing, she said. "Automated driving systems hold the promise of significantly reducing these errors and saving tens of thousands of lives in the process."