Dignity of life
The German constitutional court found that any weighing up of value of human life is illegal as it offends the dignity of the people concerned. I can buy into that, who can judge whether person A is “better” or “more valuable” than person B? Applies only to people of course, animals should lose every time imho.
For a self-driving car, I would take this as prohibiting any deliberate action that would lead to someone getting hit who otherwise would not have been hit. I.e. mitigate the collision you are heading for rather than causing a different collision.
However, the consequence of this principle would be, for example, not shooting down a hijacked plane containing one or more innocent passengers, even if the plane is heading for a crowded stadium. They made a TV courtroom drama based on this scenario.