Self-driving vehicles are in the news more often because they're already on public roads in limited tests. Waymo, a company that took over a project Google began in 2009 and has spent more than $1 billion on laser sensors and digital vision systems, is testing minivans without drivers on streets near Phoenix. It also invites requests from "early riders" who want to try the world's first driverless ride-hailing service, scheduled to start within months. A limited number of participants will use fully autonomous vehicles, as they're called, for local errands and commuting. (A two-minute Waymo video is below.) Other companies, including nearly all major auto makers, have similar projects as the industry prepares for a startling new transportation era that could redefine what “driving” means.

Waymo's small cars at first will travel only within Chandler, Ariz., a suburb of Phoenix. The test range is limited to a community the firm has mapped and simulated extensively enough to trust its cars' way-finding and decision-making abilities. Eventually, it expects the autos to serve a 600-square-mile Phoenix metropolitan region. It's the most ambitious rollout of technology that still seems like science fiction to many people. Most other companies are testing partly autonomous models in which humans and cars alternately handle driving tasks, depending on speed and situation.

While the era of self-operating cars, vans and trucks still is still in its infancy, the rollout is sure to expand dramatically – perhaps sooner than you think. One prominent study projects that 250 million connected vehicles will be in use worldwide by 2020. They'll use sensors, cameras, radar, high-performance global positioning systems, Light Detection and Ranging (LIDAR), artificial intelligence and machine learning. Public acceptance may lag behind the technology advances, a poll earlier this year suggests. More than three out of four Americans are afraid of riding in a self-driving vehicle, the Automobile Association of America (AAA) found. But after trying a partially autonomous Volvo this fall, a New York Times reporter thinks "attitudes may change quickly." David Leonhardt writes: "One of the more powerful forces in human psychology is known as the familiarity principle. After people have experience with something, they usually feel more positively about it." He was uneasy at first, but adds: "My anxiety turned to relief" when his test car "recognized that other cars were slowing and smoothly began applying the brake" as it neared a red light.

Waymo says: "After more than eight years of development, we're taking the next step toward unlocking the potential of fully self-driving technology." – Announcement last week

University publication says: "The self-driving car revolution is about to shift into overdrive." – MIT Technology Review

Boston executive says: "Autonomous vehicles will play a big role in delivering a much safer environment because they follow the rules of the road." -- Ryan Chin, co-founder of Optimus Ride, a startup working on self-driving technologies