When I sat in Google headquarters with Chris Urmson, the 38-year-old head of the company’s self-driving car team, his determination to tackle the remaining hurdles in self-driving technology was so obvious that the future immediately felt closer. He spoke evangelically of the explosion in productivity that our society will see if commuters are freed from the massive time suck of sitting behind the wheel on congested roadways. When I asked him how old kids would need to be for parents to feel comfortable putting them alone in a self-driving car, he replied, “How old are kids when parents allow them to take the subway in New York City?”