This report contains a review of literature on road tunnel resilience, including more general literature on resilience principles or aspects that could be applied to tunnels. Many definitions for “resilience” were found, but the Working Group decided on the following definition in the context of tunnels:

“The ability to prepare and plan for, absorb, recover from, or more successfully adapt to actual or potential negative effects of events or developments affecting the availability of a road tunnel. In this context, an acceptable safety level isa mandatory constraint for the availability of the road tunnel”.

It is acknowledged that the definition of resilience is not yet stabilized and that this is being discussed withing PIARC from different perspectives and committees. The work in this document will feed into the PIARC debate on resilience and the next outputs of the Working Group on resilience in the future months.

The review focusses on the following topics:

• General concepts and approaches for resilience management;
• Legislation, standards, strategies and policies;
• Criteria and requirements for resilience, availability and safety as a mandatory constraint;
• Various events and future developments to be resilient for, like weather conditions, climate change and other natural hazards like earthquakes and flooding, traffic incidents and traffic developments, calamities like fire, physical and cyber-security incidents, failure of technical or operational safety measures, including pandemics threatening the availability of the tunnel staff, maintenance and refurbishment works and technical and social developments like SMART mobility and the growing use of new energy carriers for vehicles;
• Possible measures to improve road tunnel resilience for these events;
• Organisational and managerial aspects of resilience improvement.

The report is completed with conclusions and recommendations (for decision makers and PIARC), an extensive reference list, a glossary and appendices.