Developing geometric criteria to ensure Minimal Risk Conditions for highly automated vehicles

[EN] Connected and Automated Vehicles (CAVs) represent a transformative technology with the potential to significantly enhance road safety and improve mobility for all users. However, it is important to recognize that CAVs are not infallible; there will inevitably be situations in which these vehicles must come to a stop to ensure safety. This designated stopping location is called the Minimal Risk Condition (MRC). Achieving MRC should be a standard operational capability for SAE Level 4 + vehicles, which necessitates that the automated system performs a safe Dynamic Driving Task (DDT) fallback when required, especially in instances where the human driver may not be prepared to take control of the vehicle. This study proposes various solutions to facilitate MRC, including the use of hard shoulder, Emergency Refuge Lane (ERL), and Safe Harbor (SH). Initially, we examine the advantages and disadvantages of each solution, followed by an assessment of their respective capacities ¿ experimental for ERLs and analytical for SHs. Based on these evaluations, some geometric design criteria and diverse solutions applicable to various highway types and interchanges are proposed. This work represents an important first step in addressing a critical topic that will receive further attention in the coming years, as the requirements for these zones are defined more precisely in relation to CAV penetration rates and Operational Design Domain (ODD) limitations. Consequently, it is essential that road and interchange design guidelines should be updated and adapted to incorporate these new facilities effectively.