For driverless cars to go mainstream, the companies working on them will have to convince consumers they’re as safe (or safer) than human-driven vehicles. The trick here lies in a gradual rollout. Semi-autonomous features like park assist or collision avoidance are already popping up in cars on the road today, marketed as convenience- or safety-boosting tools. (Such technology also helps manufacturers drive prices up.) That’s already gotten drivers slightly more comfortable with the idea that cars can do some driving themselves. Once those features become more widely available, it’ll mean that when cars start asking to do a little more—say, take control in a highway carpool lane—drivers will be more likely to let their car become a chauffeur.