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Ethics of automated vehicles: breaking traffic rules for road safety


In this paper, we explore and describe what is needed to allow connected and automated vehicles (CAVs) to break traffic rules in order to minimise road safety risk and to operate with appropriate transparency (according to recommendation 4 in Bonnefon et al., European Commission, 2020). Reviewing current traffic rules with particular reference to two driving situations (speeding and mounting the pavement), we illustrate why current traffic rules are not suitable for CAVs and why making new traffic rules specifically for CAVs would be inappropriate. In defining an alternative approach to achieving safe CAV driving behaviours, we describe the use of ethical goal functions as part of hybrid AI systems, suggesting that functions should be defined by governmental bodies with input from citizens and stakeholders. Ethical goal functions for CAVs would enable developers to optimise driving behaviours for safety under conditions of uncertainty whilst allowing for differentiation of products according to brand values. Such functions can differ between regions according to preferences for safety behaviours within that region and can be updated over time, responding to continual socio-technological feedback loops. We conclude that defining ethical goal functions is an urgent and necessary step from governmental bodies to enable the safe and transparent operation of CAVs and accelerate the reduction in road casualties they promise to achieve.

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Submissions used from the Law Commission consultation on automated vehicles are publicly accessible (see references). Additional materials from interviews and correspondence with industry experts are not available due to commercial sensitivity.

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  1. Operational design domain is the operating conditions under which a given driving automation system or feature thereof is specifically designed to function (SAE, 2018).

  2. Bonnefon et al. (2020) defined CAVs as vehicles that are both connected and automated and display one of the five levels of automation according to SAE International’s J3016 standard, combined with the capacity to receive and/or send wireless information to improve the vehicle’s automated capabilities and enhance its contextual awareness.

  3. In accordance with Russell & Norvig (2009), we define AI as rational agents that use data and computation to determine actions that achieve the best expected outcome.

  4. By ‘traditional’, we mean approaches based on deep learning to determine optimal outcomes.

  5. Respondents included vehicle manufacturers, CAV developers, industry bodies, national and sub-national transport organisations, charities, technology companies, police forces, law firms and private individuals (Law Commission, 2019).

  6. Term used in Moral Theory.


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The authors would like to thank Dr. Nadisha-Marie Aliman for her helpful advice on various technical issues discussed in this paper and the individual academic and industry experts who engaged with our questions on CAV rule compliance, representatives from MIT, RWTH Aachen University and the Metropolitan Police for their insights in support of this paper and all people in our network that provided input to this paper with their ideas and opinions around behaviour of CAVs in case of breaking traffic rules.


No funding was received to assist with the preparation of this manuscript.

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All authors contributed to the drafting of the manuscript. All authors have read and approved the final manuscript.

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Correspondence to Nick Reed.

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Reed, N., Leiman, T., Palade, P. et al. Ethics of automated vehicles: breaking traffic rules for road safety. Ethics Inf Technol 23, 777–789 (2021).

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