Self-driving cars will probably save a lot of lives in the future. But right now the tech is new, and most of it requires human intervention. Experts refer to several levels, one through five, of automation in cars. A fifth-level car would have no steering wheel or gas pedal. Several cars on the market now fit into the middle category, requiring human intervention with some autonomous features. Marketplace Tech host Molly Wood spoke with Missy Cummings, director of the Humans and Autonomy Lab at Duke University, about the risks of having humans only partly in control. (This interview originally aired May 2.)