The battery-powered sedan broadcasts a request to merge into the next lane, and other nearby vehicles automatically adjust as it glides over and exits the highway. Inside, the passenger finishes a quick email check, then clicks on a monitor to catch up with the day's news. For fans of automated vehicles (AVs), it's the holy grail of transportation: Cars would pilot themselves in an orderly fashion, making driving safer, cheaper, and faster. Easy transportation would be available to everyone without the environmental impacts or traffic congestion seen today. But those benefits could be offset or canceled out altogether, skeptics say, if the technology inadvertently encourages more driving among people who can't currently drive, and among commuters who might opt to travel all the way into cities rather than "park and ride."