  A collision hazard measure that has the essential characteristics to provide
a measurement of safety that will be useful to AV developers, traffic
infrastructure developers and managers, regulators and the public is introduced
here. The Streetscope Collision Hazard Measure (SHM) overcomes the limitations
of existing measures, and provides an independent leading indication of safety.
* Trailing indicators, such as collision statistics, incur pain and loss on
society, and are not an ethically acceptable approach. * Near-misses have been
shown to be effective predictors of incidents. * Time-to-Collision (TTC)
provides ambiguous indication of collision hazards, and requires assumptions
about vehicle behavior. * Responsibility-Sensitive Safety (RSS), because of its
reliance on rules for individual circumstances, will not scale up to handle the
complexities of traffic. * Instantaneous Safety Metric (ISM) relies on
probabilistic predictions of behaviors to categorize events (possible,
imminent, critical), and does not provide a quantitative measure of the
severity of the hazard. * Inertial Measurement Unit (IMU) acceleration data is
not correlated with hazard or risk. * A new measure, based on the concept of
near-misses, that incorporates both proximity (separation distance) and motion
(relative speed) is introduced. * Near-miss data has been shown to be
predictive of the likelihood and severity of incidents. The new measure
presented here gathers movement data about vehicles continuously and a
quantitative score reflecting the hazard encountered or created (from which the
riskiness or safeness of the behavior of vehicles can be estimated) is computed
nearly continuously.
