portfolio but also of its work on self-driving technology.

Days after delivering the first Bolts to customers in California last week -- and fulfilling CEO Mary Barra's promise to launch the vehicle by year end -- GM revealed plans to start building a test fleet of autonomous Bolts in January on the same Michigan assembly line as the regular version of the car.

Barra also said the automaker immediately would begin running autonomous Bolts on public roads in the Detroit area for the first time.

Michigan will become GM's primary region to test autonomous technology in cold weather and snow -- conditions that pose significant challenges for the lidar, sensors and cameras that enable the vehicles to operate on their own.

The moves, made in response to new laws that give Michigan the nation's most liberal autonomous-vehicle regulations, represent a significant expansion of GM's work to validate the technology. GM plans to roll out autonomous Bolts to Lyft, the ride-hailing company it invested $500 million in last winter, within several years; officials declined last week to give a more specific time frame.

"We have the opportunity and the responsibility to create a new model of personal transportation," Barra said. "We're ensuring that our [autonomous vehicles] can operate safely across a full range of road, weather and climate conditions."

GM is in the early stages of ramping up production of the Bolt at its plant in Orion Township, Mich. It's building about 100 Bolts a day intermixed with the Chevy Sonic subcompact car.

The company said it will expand sales to the Northeast and mid-Atlantic regions this winter before distributing it to EV-certified dealerships nationwide around mid-2017.

That's about when Tesla has said it plans to start building the Model 3, which has a similar range and price as the Bolt. However, many analysts are doubtful that Tesla will launch the Model 3 before 2018, which would give the Bolt at least a year with the market to itself. GM aims to leverage that advantage even more by building autonomous test versions of the Bolt before Tesla starts making the Model 3.