One of the many ways self-driving cars will impact the world is with organ shortages. It's a morbid thought, but the most reliable sources for healthy organs and tissues are the more than 35,000 people killed each year on American roads. According to the book "Driverless: Intelligent Cars and the Road Ahead," 1 in 5 organ donations comes from the victim of a vehicular accident. Since an estimated 94 percent of motor-vehicle accidents involve some kind of a driver error, it's easy to see how autonomous vehicles could make the streets and highways safer, while simultaneously making organ shortages even worse. Slate reports: As the number of vehicles with human operators falls, so too will the preventable fatalities. In June, Christopher A. Hart, the chairman of the National Transportation Safety Board, said, "Driverless cars could save many if not most of the 32,000 lives that are lost every year on our streets and highways." Even if self-driving cars only realize a fraction of their projected safety benefits, a decline in the number of available organs could begin as soon as the first wave of autonomous and semiautonomous vehicles hits the road -- threatening to compound our nation's already serious shortages. We're all for saving lives -- we aren't saying that we should stop self-driving cars so we can preserve a source of organ donation. But we also need to start thinking now about how to address this coming problem. The most straightforward fix would be to amend a federal law that prohibits the sale of most organs, which could allow for development of a limited organ market. Organ sales have been banned in the United States since 1984, when Congress passed the National Organ Transplant Act after a spike in demand (thanks to the introduction of the immunosuppressant cyclosporine, which improved transplant survival rates from 20-30 percent to 60-70 percent) raised concerns that people's vital appendages might be "treated like fenders in an auto junkyard." Others feared an organ market would exploit minorities and those living in poverty. But the ban hasn't completely protected those populations, either. The current system hasn't stopped organ harvesting -- the illegal removal of organs from the recently deceased without the consent of the person or family -- either in the United States or abroad. It is estimated that, worldwide, as many as 10,000 black market medical operations are performed each year that involve illegally purchased organs. So what would an ethical fix to our organ transplant shortage look like? To start, while there's certainly a place for organ donation markets in the United States, implementation will be understandably slow. There are, however, small steps that can get us closer to a just system. For one, the country could consider introducing a "presumed consent" rule. This would change state organ donation registries from affirmative opt-in systems (checking that box at the DMV that yes, you do want to be an organ donor) to an affirmative opt-out system where, unless you state otherwise, you're presumed to consent to be on the list.