SAN RAMON, Calif. — Electronic chimes sounded as the self-driving minibus halted its crawl through the parking lot of an upscale office park here. There was no obvious reason for the stop, so its operator made a note to report it, then used a touch screen to restart the shuttle’s test drive.

The bright red, 12-passenger vehicle, which maxes out at 12 mph and was designed by French firm EasyMile, is part of an effort to use autonomous technology to improve access to transit stations in the area. But first, as the unscheduled stop on a breezy April day showed, the shuttle needs extensive testing to make sure it’s safe for public roads.

California regulations allow testing of self-driving vehicles, even as a lack of federal rules prohibit commercial sales or interstate travel. That means the EasyMile vehicle can legally operate on public streets in a limited capacity.

California in 2012 became one of the first states to enact rules of the road for vehicles using various levels of automation, spurred by what was then Google’s self-driving project — now Waymo, a separate unit of the Alphabet parent corporation — and other home-state developers.

A 2016 state law allows the testing at Bishop Ranch, a 100-acre office park about 20 miles east of San Francisco. There are 30,000 workers here, including employees of General Electric, AT&T, Chevron and Toyota.