Think quickly: You are a bystander witnessing a runaway trolley that is careening toward five workers. You have just two choices: One, pull a switch diverting the trolley onto another track, where one worker would be killed, or two, do nothing and let the trolley hit and kill the five workers.

This thought experiment — the so-called “Trolley Problem” — is an infamous moral dilemma popularized by the Massachusetts Institute of Technology moral philosopher, Judith Thomson. And it just got one step closer to reality with the death of Elaine Herzberg, the 49-year-old woman who is reportedly the first victim of a self-driving car on a U.S. public road.