Self-driving cars will rely on machine learning, a branch of artificial intelligence that allows computers, or in this case cars, to learn over time. Since cars will learn how to adapt to the driving environment on their own, they could learn to favor certain outcomes.

“Even in instances in which no explicit ethical rule or preference is intended, the programming of an HAV may establish an implicit or inherent decision rule with significant ethical consequences,” NHTSA wrote in the report, adding that manufacturers must work with regulators to address these situations.

Rahwan said programming for specific outcomes isn’t the right approach, but thinks companies should be doing more to let the public know that they are considering the ethics of driverless vehicles.

“In the long run, I think something has to be done. There has to be some sort of guideline that’s a bit more specific, that’s the only way to obtain the trust of the public,” he said.