People have been taking driving tests for many decades. If (or when) self-driving cars become commonplace, vehicles could also need to pass tests and obtain licenses.\n\n\nAuto-safety researchers at the University of Michigan proposed this intriguing idea.\u00a0"Current prototypes of self-driving vehicles are not perfect. For example, some of them occasionally cross the centerline on curves even in good weather conditions," wrote Michael Sivak and Brandon Schoettle of the university's Transportation Research Institute, in a just-released white paper.\u00a0\n\n\nCoincidentally, that very mishap\u00a0occurred this week when a partially-autonomous Tesla started to swerve across the road into the path of an oncoming car. Fortunately, the human driver intervened in time to avoid a collision, but the incident highlights the need to thoroughly evaluate self-driving car safety and reliability.\n\nRoad hazards, weather present challenges for self-driving vehicles\n\nSivak and Schoettle don't believe every single self-driving car will need to be tested and licensed, of course. However, as new models of autonomous vehicles are released, they should be required to pass tests that measure their vision, knowledge of traffic laws, and ability to drive in traffic before being allowed on the roads, the men say.\n\n\nIt's easy for computers to learn the rules of the road; they can simply be programmed with the information contained in a driver's handbook. Onboard computers can contain information from all 50 states, and the cars can use GPS to determine location and the state laws that need to be followed.\n\n\nVision is a much trickier proposition.\u00a0It's one thing for a human or a robot to see well on a clear day. Rain, snow, and darkness make it much more difficult to recognize objects or hazards, so, self-driving cars will also need to be tested under a variety of weather conditions, according to the researchers. (Google recently said it won't offer self-driving cars in areas where it snows, at least not initially.)\n\nDifferent degrees of licenses for different self-driving cars\n\nA potential solution to the weather problem could be a "graduated" license, the researchers say. Self-driving cars could be licensed to drive in good weather, but not in the snow. Similarly, if a car has a problem seeing at night, it could be limited to driving during the day. When new technological advances are integrated into the vehicles, the models could get licenses that let them operate in any weather or at any hour.\n\n\nComputer's also have difficulty with pattern recognition \u2014 a skill that humans excel at. This is why many websites use CAPTCHAs, those random jumbled codes, to prevent computers from automatically accessing websites. The University of Michigan\u00a0researchers cite two common road conditions that could confuse computers: downed power lines across roadways, and flooded underpasses. Self-driving cars should be tested accordingly for their abilities to recognize difficult patterns, they say.\n\n\nAlthough each state has its own set of requirements for drivers' licenses, the federal government has the power to set national standards for vehicles. A licensing requirement for autonomous vehicles could be established at the national level, though it would need to take state laws into account, according to Spivak.\n\n\nThe notion of licenses for cars also raises another intriguing question: If a self-driving car drives too fast or blows through a stop sign, who gets the ticket?