The everyday moral challenges of self-driving cars

As the most recent crash — in which a self-driving car killed a pedestrian in Tempe, Ariz. — demonstrates, the mundane, everyday situations at every crosswalk, turn, and intersection present much harder and broader ethical quandaries.

The initial challenge of driverless cars is designing machines that drive more competently than humans. But the heavier lift is for society to decide how a machine should make the many routine ethical decisions that arise when a car is in motion.