With the increasing number of tunnels under construction or in planning throughout the world, and the growing volume of traffic using existing tunnels, safety issues are becoming increasingly important. Incidents and accidents in road tunnels may be no more frequent than those on the open road, indeed road tunnels can provide a safer, more controlled driving environment for road users. However, the consequences of major incidents in the confined tunnel environment are potentially significantly more severe than on the open road and usually raise stronger reactions from the public.
In a modern road tunnel, safety is assured by taking an integrated approach. Sets of well developed tools - like risk assessment, safety inspections and safety procedures - are available to help achieve the safety objectives from the initial planning and design stages of a new tunnel, through to the operation and upgrading of existing tunnels."
An appropriate level of safety for tunnels that is comparable with that on the open road is achievable through a structured and integrated approach to the design and operation of tunnels that focuses on the prevention of serious incidents and the mitigation of consequences through the encouragement and facilitation of self rescue in the first instance and the subsequent effective intervention of the emergency services.
Important lessons can be learned from the experience of past tunnel incidents, these are discussed in Experience from past tunnel incidents. Previous tunnel incidents have led to an increased international awareness and interest in tunnel safety impacts; indeed, following the report of the investigation after the Mont Blanc fire in 1999, a number of countries throughout the world initiated a review and update of national standards and guidelines for tunnel safety.
The United Nations Economic Commission for Europe (UNECE) established a group of experts on road tunnel safety, with PIARC representation, which produced Recommendations in 2001 on all aspects of road tunnel safety. These recommendations have contributed to the development and update of international standards for tunnel safety. In Europe, the European Commission prepared a Directive on minimum safety requirements for road tunnels on the Trans European Road Network which entered into force in 2004.
Action has also been taken in other parts of the world. In the USA, the national standard for fire safety in road tunnels (NFPA 502) has undergone a periodic update, taking account of developments through research and learning from past tunnel incidents.
The minimum requirements set out in the European Directive relate to tunnels that are on the Trans European Road Network. In countries throughout Europe and elsewhere, the regulations and requirements for tunnel safety may be more onerous than the requirements of the Directive. Such standards may be derived to account for the particular circumstances in the individual countries and to deal with tunnels that are not governed by the Directive, such as particular urban tunnels for example.
The PIARC Technical Committee on Road Tunnel Operation has advanced the main issues regarding tunnel safety through the publication of a series of reports under dedicated Working Groups. In addition to its own activities and the legislative developments, a number of research projects and thematic networks, mainly in Europe, have contributed to the knowledge and understanding of the principles of tunnel safety and guided the tunnels community to the conclusion that there is a need for an integrated approach to road tunnel safety. These general principles are the subject of General principles of this Manual and the integrated approach is addressed in Safety elements and integrated approach.
More details on the international cooperative efforts aimed at better understanding and improving tunnel safety can be found in the following documents:
Further to these activities, PIARC supports the Committee on Operational Safety of Underground Facilities (ITA-COSUF) of the International Tunnel and Underground Space Association (ITA) as an international network for exchange of experience and promotion of safety.
Key to the integrated approach to road tunnel safety is the establishment of safety level criteria, the analysis of safety and the evaluation of the balance between the costs and the benefits to achieve an acceptable level of safety. Fundamental to this is risk assessment, an essential tool for tunnel safety management, discussed in section Risk assessment.
Of particular importance and requiring particular attention in the analysis and evaluation of tunnel safety are fires in tunnels, discussed in section Principles and tools for fire safety and the transport of dangerous goods, discussed in section Dangerous goods.
To maximise the effectiveness of tunnel safety management, certain tools are needed to support strategy, to drive critical decisions and keep a constant and traceable view of all safety issues over a tunnel's lifetime. The three major tools regarding tunnel safety management are the Safety Documentation; the Collection and Analysis of Incident Data and Safety Inspections. These are described in some detail in Safety procedures.
New requirements regarding safety, as well as increase in traffic, lead to upgrading existing tunnels. This raises specific problems which are examined in Assessing and improving safety in existing tunnels.
Input to this Chapter was coordinated by Working Group 2 of the C4 committee (2008-2011) in which: