The researchers first polled 1,928 internet users about how moral they rated an autonomous car’s response to various hypothetical crashes. A pattern became clear: The higher the number of pedestrians that would be spared, the more participants felt it was ethical for the car to sacrifice a passenger—even when they imagined that person was a family member.

Things got more complicated, though, when participants were asked whether the government should require driverless cars to minimize pedestrian deaths at the expense of passengers, and if they would buy a car programmed to do so. People liked the idea of autonomous cars that would kill one pedestrian to save 10 others. They also liked the idea of other motorists owning cars that would sacrifice passengers to protect pedestrians. But they were less likely to want to own such a car themselves or to support the government enforcing this kind of sacrifice. Overall, the respondents were nearly three times less likely to buy a car designed to let the occupants die to spare pedestrians than one with no such programming.