Suppose that a driverless car is headed towards five pedestrians. It can stay on course and kill them or swerve into a concrete wall, killing its passenger. This ethical dilemma is a difficult one - and it appears that people cannot decide which outcome is better. New research shows that people generally approve of cars programmed to sacrifice their passengers to save others, but these same people would not want to be in the car themselves. Self-driving cars are expected to usher in a new era of mobility, safety and convenience.

In a series of surveys published Thursday in the journal Science, researchers asked people what they believe a driverless car ought to do in the following scenario: A group of pedestrians are crossing the street, and the only way the car can avoid hitting them is by swerving off the road, which would kill the passengers inside. The participants generally agreed that the cars should be programmed to sacrifice their passengers if doing so would save many other people. This, broadly speaking, is a utilitarian kind of answer -- one aimed at preserving the greatest possible number of lives. But there's one problem: The people in the survey also said they wouldn't want to ride in these cars themselves. It would be OK for others to buy them, the participants said, but they personally would not.