Self-driving vehicles have been proposed as a solution for the rapidly increasing number of fatal traffic accidents, which now cause 1.3 million deaths each year.

    While we have made great progress in advancing self-driving technology, we have yet to explore how autonomous vehicles will be programmed to deal with situations that endanger human life, according to a new study published in Frontiers inBehavioral Neuroscience.

    To understand how self-driving cars might make these judgments, the researchers looked at how humans deal with similar driving dilemmas.

    When faced with driving dilemmas, people show a high willingness to sacrifice themselves for others, make decisions based on the victim's age and turn onto sidewalks to minimize the number of lives lost. Ethical（伦理的）guidelines tend to disagree with human instincts（本能） in this case, saying that no life should be valued above another.

    “The technological advancement and adoption of autonomous vehicles are moving quickly but the social and ethical discussions about their behavior are lagging behind,” says lead author Lasse T. Bergmann from University of Osnabrück, Germany.

    Automated vehicles will eventually outperform theirhuman counterparts, but there will still be circumstances where the cars must make an ethical decision to save or possibly risk losing a human life.

    The study is especially relevant considering earlier this year a self-driving Uber car struck and killed a passenger in Arizona, in an incident widely regarded as the first death resulting from an autonomous vehicle.

    An ethics commission launched by the German Ministry for Transportation has created a set of guidelines, representing its members' best judgement on a variety of issues concerning self-driving cars. These expert judgments may, however, not reflect human instinct.

    Bergmann and colleagues developed a virtual reality experiment to examine human instinct in a variety of possible driving situations. It was based on the well-known ethical thought experiment—the trolley problem.

    In this experiment, there is a trolley running down the railway tracks. Ahead, on the tracks, there are five people tied up, unable to move, and the trolley is headed straight for them. A person is standing some distance off in the train yard, next to a lever（操作杆）.If he pulls this lever, the trolley will turn to a different set of tracks. However, there is one person tied up on the side track. Does the person choose to pull the lever and kill one person, or do nothing and let five people die?

    Bergmann recognized that the majority of people would not approve of the proposal made by the ethics commission that a passenger in the vehicle should not be sacrificed to save more people. “We find people chose to save more lives, even if this involves turning onto the sidewalk, endangering people uninvolved in the traffic incident,” said Bergmann, “Furthermore, subjects considered the factor of age, for example, choosing to save children over the elderly.” He also realized further discussion and research were needed. “Driving requires a complex weighing of risks versus rewards, for example, speed versus the danger of a critical situation,” Bergmann explained.