  This paper presents an overview of Waymo's approach to building a reliable
case for safety - a novel and thorough blueprint for use by any company
building fully autonomous driving systems. A safety case for fully autonomous
operations is a formal way to explain how a company determines that an AV
system is safe enough to be deployed on public roads without a human driver,
and it includes evidence to support that determination. It involves an
explanation of the system, the methodologies used to develop it, the metrics
used to validate it and the actual results of validation tests. Yet, in order
to develop a worthwhile safety case, it is first important to understand what
makes one credible and well crafted, and align on evaluation criteria. This
paper helps enabling such alignment by providing foundational thinking into not
only how a system is determined to be ready for deployment but also into
justifying that the set of acceptance criteria employed in such determination
is sufficient and that their evaluation (and associated methods) is credible.
The publication is structured around three complementary perspectives on safety
that build upon content published by Waymo since 2020: a layered approach to
safety; a dynamic approach to safety; and a credible approach to safety. The
proposed approach is methodology-agnostic, so that anyone in the space could
employ portions or all of it.
