Cover: Safe Enough

Safe Enough

Approaches to Assessing Acceptable Safety for Automated Vehicles

Published Oct 29, 2020

by Marjory S. Blumenthal, Laura Fraade-Blanar, Ryan Best, J. Luke Irwin


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Research Questions

  1. In what ways can AV safety can be assessed?
  2. How can measurements be used to assess AV safety?
  3. How can processes be used to assess AV safety?
  4. How can thresholds be used to assess AV safety?
  5. How do different approaches to assessing AV safety compare and interact with each other?
  6. How can communication about AV safety be improved?

Establishing whether automated vehicles (AVs) are acceptably safe is not straightforward, and continual technology modification adds complication. RAND Corporation researchers analyzed three categories of approach—measurements, processes, and thresholds—and noted the different kinds of evidence associated with each, the ways in which different approaches can be used together, and the degree to which stakeholder groups agree on the merits of these approaches. This report complements discussion of measurement and analytical issues with a discussion of challenges in communicating about AV safety, especially to the general public. Its recommendations are aimed at both industry and government.

Key Findings

Different approaches to assessing AV safety—measurement, process, and thresholds—complement each other, with no one best approach

  • Leading measures remain key to assessing AV safety given the lack of crash-based lagging measures.
  • Among leading measures, approaches to roadmanship, the ability to drive on the road safely without creating hazards and responding well to hazards created by others, are growing.

Because existing measures are insufficient to assess AV safety, more attention is being paid to processes—steps taken by developers and how these steps are implemented—and what they indicate

  • These processes include safety-relevant standards-setting activities, a growing emphasis on safety culture, and widening use of safety cases (collections of assertions defining how safety is being promoted and assessed).
  • Compliance with regulations is also a process, but its reach remains smaller than that for conventional vehicles.

Thresholds—which can be qualitative as well as quantitative—are another way to assess AV safety

  • The most straightforward threshold is human driving performance.
  • Other thresholds relate to AV performance and absolute goals.
  • Thresholds will evolve as technology develops, commercial use expands, and expectations rise. Meeting thresholds is not a one-time achievement.

Communicating about AV safety shapes public trust

  • Although messages about AV safety come from many sources, the provenance of messages is not always obvious to the general public.
  • A RAND American Life Panel survey demonstrates the importance of how communications with the general public are structured.
  • The public has the greatest trust in AV safety messages from government.


  • AV developers and the larger AV research community should continue to advance and integrate leading measures, including roadmanship. An industry consortium could help.
  • Developers should forge uniform and transparent approaches to presenting evidence for meeting safety thresholds. These would factor in differences in use cases, operational design domains, and more, and they could focus on better-than-average driving as a threshold.
  • The U.S. Department of Transportation should support further research into human drivers to enable the comparisons that stakeholders seek. Such research should address differences in operational design domains.
  • AV developers should collaborate with state and local leaders to bring their vehicles into communities around the country. Direct exposure to AVs supports public understanding.

Research conducted by

This research was commissioned by the Uber Advanced Technologies Group and conducted in the Community Health and Environmental Policy Program within RAND Social and Economic Well-Being.

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