  The large-scale deployment of automated vehicles on public roads has the
potential to vastly change the transportation modalities of today's society.
Although this pursuit has been initiated decades ago, there still exist open
challenges in reliably ensuring that such vehicles operate safely in open
contexts. While functional safety is a well-established concept, the question
of measuring the behavioral safety of a vehicle remains subject to research.
One way to both objectively and computationally analyze traffic conflicts is
the development and utilization of so-called criticality metrics. Contemporary
approaches have leveraged the potential of criticality metrics in various
applications related to automated driving, e.g. for computationally assessing
the dynamic risk or filtering large data sets to build scenario catalogs. As a
prerequisite to systematically choose adequate criticality metrics for such
applications, we extensively review the state of the art of criticality
metrics, their properties, and their applications in the context of automated
driving. Based on this review, we propose a suitability analysis as a
methodical tool to be used by practitioners. Both the proposed method and the
state of the art review can then be harnessed to select well-suited measurement
tools that cover an application's requirements, as demonstrated by an exemplary
execution of the analysis. Ultimately, efficient, valid, and reliable
measurements of an automated vehicle's safety performance are a key requirement
for demonstrating its trustworthiness.
