The report specifically mentions a number of other studies and claims it improves on their methodology, and seems to want to have their methodology become the "gold" standard of measuring SDV vs HDV performance:

  "This methodology establishes a foundation for future research into the safety impact potential of ADS and offers a framework for assessment as these systems continue to scale and develop."

Or:

  "By analyzing an unprecedented volume of autonomous miles, introducing a novel benchmark, and utilizing third-party liability insurance claims, we aim to set a new standard for ADS safety evaluation."

Which leads me to worry that they are pushing for this to be considered comparative, and they want policy to be influenced by their claims. And they do:

  "Our findings have the potential to significantly impact policy decisions, insurance practices, and public acceptance of ADS technology, contributing to the broader societal dialogue on the future of autonomous transportation."

So I would like for them to compare to median non-impaired human driver with a car in good order (both in time-to-destination and safety), aggregate those over time of day, week and year (basically ensure identical driving conditions between comparison miles), adding claim dollar amount as weight for how severe the incident was. I believe that would be a great start.

With them being Google and already tracking most Android phones as they go through traffic (they use this for traffic conditions), they do have a very rich data set they could compare to as well, but excluding that, they could exclude insurance claims which have happened in conditions they don't operate in (claims will always have time of event and location).