Regulators, certification bodies and developers are scrutinizing what safe deployment at scale requires.

Industry discussion on level 4 autonomy often centers on what the vehicle can perceive and decide.

That discussion is well-founded. Accurate perception, sound decision-making and handling the unexpected are difficult problems, and real progress toward solving them is being made.

But perception and decisions alone are not the whole story. Regulators require something more: proof that the overall system behaves reliably, isolates faults before they escalate and never operates outside the boundaries it was designed for.