After a closely watched vote, driverless cars, once a Silicon Valley fantasy, have become a 24-hour-a-day reality in San Francisco. Are autonomous vehicles an interesting and safe transportation alternative? Or are they a nuisance and a traffic-blocking disaster waiting to happen?Cade Metz, who covers technology for The Times, describes the unique challenges of coexisting with cars that drive themselves.Guest: Cade Metz, a technology correspondent for The New York Times.Background reading: On Monday, Waymo began letting the public pay for rides in its driverless cars in San Francisco. The New York Times dispatched three reporters around the city to test the service.Local officials are worried that state regulators have been too eager to embrace plans for round-the-clock driverless taxi services.For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.