National Academies Press: OpenBook

Design Fires in Road Tunnels (2011)

Chapter: Chapter One - Introduction

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Page 6
Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2011. Design Fires in Road Tunnels. Washington, DC: The National Academies Press. doi: 10.17226/14562.
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Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2011. Design Fires in Road Tunnels. Washington, DC: The National Academies Press. doi: 10.17226/14562.
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Page 7
Page 8
Suggested Citation:"Chapter One - Introduction." National Academies of Sciences, Engineering, and Medicine. 2011. Design Fires in Road Tunnels. Washington, DC: The National Academies Press. doi: 10.17226/14562.
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Page 8

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7BACKGROUND This synthesis reports on the state of knowledge and practice for design fires in road tunnels. It includes a review of the literature and research on current practices. A survey of trans- portation agencies and tunnel owners to obtain their expe- riences and practices with tunnel fire life safety systems such as ventilation, fire protection, and detection is included. The survey solicited transportation agency opinions regarding problems with these systems, gaps in the current knowledge, and what improvements they would like to see made. There has been considerable growth in tunnel construction in the United States and worldwide, as well as an increase in road traffic. This has resulted in a societal concern with tun- nel safety. Over the past several years, fires in road tunnels from large vehicles have shown the risks and consequences of inadequate prevention. More than 50 individuals have died in road tunnel fires in Europe over the last 10 years. The national fire analysis and research that was done in 2008 concluded that a fire occurs in a structure once every 61 s. Fires occur in vehicles once every 134 s, and there were 236,000 vehicle fires in the United States in 2008. In 2008, 350 individuals died in highway vehicle fires in the United States. Recent catastrophic tunnel fires have not only resulted in loss of life and severe property damage, but also left the public with a decrease in confidence in the building and oper- ation of new and existing tunnels. Although over the years much research has been carried out on tunnel safety, there are still many gaps in tunnel fire information that can cause dif- ficulties for tunnel designers. Several NCHRP research studies, work by the TRB Ac- cess Management Committee, and publications by TRB, AASHTO, ITE, FHWA, NTSB and others have provided information and materials to state and local agencies on tunnel safety. NCHRP Report 525: Volume 12, Making Transportation Tunnels Safe and Secure (TCRP Report 86) addresses tunnel safety and security issues (1). The Inter- national Technology Scanning Program, sponsored by AASHTO and FHWA, issued a report in 2006, Underground Transportation Systems in Europe: Safety, Operations, and Emergency Response, with the objective of discovering what is being done internationally for underground transportation systems with regard to safety, operations, and emergency response (2). A number of recommendations and design manuals have been issued by the FHWA, including Road Tunnel Design and Construction Manual 2010 (3) and Rec- ommendations for Bridge and Tunnel Security (4). A Do- mestic Tunnel Scan conducted in August and September 2009, lead to the report, Best Practices for Roadway Tunnel, Design, Construction, Maintenance, and Operation (5). This synthesis report provides a literature review and syn- thesis analysis of the latest available information, current prac- tice, knowledge, and relevant research information related to design fires in road tunnels. It includes a collection and documentation of statistical data of fire incidents in road tun- nels since 1949 through the last decade; collection and docu- mentation of existing data from fire tests in road tunnels; and identification of the gaps in this information. This informa- tion was organized into a concise document that describes current knowledge and practice. The final report provides practical solutions for fire life safety problems. The report includes: • Different design standards, guidelines, documents, and codes used worldwide. • A synthesis of the results of different international proj- ects and their recommendations. • Tunnel fire events worldwide and their consequences. • Tunnel fire tests results, including full- and small-scale experiments and gaps in those tests. • The latest developments, lessons learned, and identi- fication of gaps in available information to provide a foundation for design guidance. This synthesis report is focused on tunnel fire dynamics and means of fire management for design guidance. The objective of the study was to synthesize the available infor- mation related to design fires in roadway tunnels, identify gaps in that information, and provide a framework for design guidance. The information obtained for this project can help state departments of transportation (DOTs), industry, and other stakeholders as a basis for design guidance in making tunnels safer. PROJECT OVERVIEW Every tunnel is unique, which makes it difficult to generalize design, and fire safety needs to be reviewed in an integral fashion. This comprises all aspects of fire safety, including CHAPTER ONE INTRODUCTION

the severity of incidents, consequences of fires, human re- sponse, structural response, systems response, emergency re- sponse teams, and tunnel operators. The design fire parameters used for the design of tunnel emergency ventilation and fire life safety systems have a sig- nificant impact on the tunnel design and users’ safety. The key criteria are the fire size and heat release rate (HRR), fire growth and decay rate, smoke production, resultant temperatures, and fire duration. If both the growth rate and the peak fire size are assumed to be too slow in the early design stage, the design changes may result in additional surface penetrations, larger fan plants, and additional spaces and evacuation routes. More than 30 years ago minimum attention was paid to fires in tunnel design. Tunnel ventilation system design was driven by carbon monoxide (CO) dilution requirements for normal operation and the American Society for Heating, Refrigeration, and Air Conditioning (ASHRAE) recom- mendations of 100 cfm/lane/ft (0.155 m3/s/lane/m) of supply and exhaust airflow. However, tunnel accidents in recent years have drawn widespread attention to the risks of fires in tunnels with two distinct consequences. First, the fires themselves have resulted in fatalities, injuries, and struc- tural damages, as well as lengthy tunnel shutdowns result- ing in adverse economic impacts. Second, the perceived risk of fire is also likely to have discouraged tunnel use and, in some cases, the actual construction of tunnels. NFPA 502: Standard for Road Tunnels, Bridges, and Other Limited Access Highways, updated in 2011, is the primary national document that provides guidelines for fire and life safety requirements for U.S. road tunnels. This standard is gen- erally updated every 3 years based on the latest information on tunnel fires, development of technology, and the experiences of tunnel owners, agencies, first responders, designers, and vendors. The latest Standard includes 13 chapters and an annex of explanatory material that covers limited access high- ways, bridges, road tunnels, and roadways beneath air-right structures and sets design requirements for fire life safety sys- tems, structures, and emergency response procedures. ASHRAE established Technical Committee TC 5.9 on Enclosed Vehicular Facilities to address tunnel safety issues during bi-annual ASHRAE meetings through conferences, transactions, forums, and seminars. Since 1999, a number of major tunnel fire incidents have occurred in Europe. As a result, several international and European research projects have been focused on the design for controlling fires. Ample experience comes from Australia and Japan, who have also had major tunnel fires. Every year there are a number of international conferences, symposiums, forums, and seminars on tunnel safety and the ventilation of vehicular tunnels. This synthesis project focuses on the latest international experience and knowledge in the design of con- trolling tunnel fires, as well as the survey results from ques- 8 tionnaires completed by tunnel owners and agencies regarding best practice in tunnel safety. This study synthesizes the available information, prac- tice, and knowledge related to design fires in road tunnels and identifies gaps in that information to provide a founda- tion for design guidance. A design fire is characterized by a number of parameters including the temperature, fire heat release rate (FHRR), fire growth rate, fuel load, and products of combustion. The sources of information used for developing this syn- thesis included the literature search, a survey, and interviews with the following stakeholders: owners, operators, designers, emergency responders, government agencies, relevant pro- fessional associations, and so forth. The literature search in- cluded national and international standards and guidelines on road tunnel safety; publications of international organizations such as the World Road Association (Association mondiale de la route; PIARC), United Nations, and European Union; reports on major international studies; papers presented at national and international symposiums; and books, magazines, and other publications. The objectives of this study were to: • Document significant fire incidents, domestic and inter- national, in road tunnels. • Review existing data from fire tests in road tunnels and identify gaps in testing. • Collect data on the application and effectiveness of fixed fire suppression systems and how these might modify the design fire size. • Document the effects of various ventilation conditions, tunnel geometry, and structural and nonstructural com- ponents of a tunnel on design fire characteristics. • Document the impact of alternate fuel vehicles on design fires. • Present design fire issues relevant to fire suppression system designs and gaps in available information. • Establish the state of practice in computer and scale- modeling efforts. • Provide exit strategies and motorist notification systems. • Review design guidance information on the issues that need to be considered in setting design fire sizes and establishing next steps. • Seek out information on combined use tunnels. DESCRIPTION OF THE SURVEY PROCESS The survey process involved the development and distribu- tion of an on-line questionnaire that focused on identifying the range of current practices in design and procedures that deal with fires in road tunnels. The primary candidates for completing the questionnaire were transportation agency staff, primarily at the state DOT level, to obtain as broad a repre- sentation of current tunnel fire management practices as pos- sible. Input was solicited from the national tunnel agencies

9and operating authorities. The same questionnaire was sent to international agencies in Canada, Australia, Hungary, Korea and Sweden. The questionnaire responses were a vital source of information for this study. The questionnaire information was also distributed at the winter 2010 ASHRAE Meeting of the Technical Committee 5.9 on Enclosed Vehicular Facilities to solicit voluntary participation. The questionnaire was administered in the following manner: • A targeted list of key individuals at state DOTs was developed. Topic Panel members reviewed the survey distribution list and made changes where necessary and added contact information for any suggested agencies to include in the survey. • Electronic copies of the questionnaire were distributed to any willing participants. • Nonrespondents at state DOTs were contacted with follow-up reminders to encourage responses. Questionnaire recipients were asked to either complete the questionnaire themselves or forward the questionnaire to another, more appropriate individual within their agency. In addition, a recipient could choose to forward the ques- tionnaire hyperlink to individuals in multiple divisions within the agency. Chapters two through seven, nine, and thirteen document the literature review; results of the survey are summarized in chapter eight; chapter ten compiles design guidance, stand- ards, and regulation; chapter eleven reviews design fire sce- narios for fire modeling; chapter twelve discusses fixed fire suppression; and chapter fourteen presents the conclusions and areas for further study. Appendix A includes the survey questionnaire, Appendix B is a list of the responding agencies, and Appendix C is the Summary of the Survey Questionnaire Responses. Appen- dixes D through G present web-only information on tunnel safety projects, fire tests, national and international standards requirements, and past tunnel fires.

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TRB’s National Cooperative Highway Research Program (NCHRP) Synthesis 415: Design Fires in Road Tunnels information on the state of the practice of design fires in road tunnels, focusing on tunnel fire dynamics and the means of fire management for design guidance.

Note: On September 20, 2011, the following errata was released related to NCHRP Synthesis 415. The electronic version of the publicaiton was changed to reflect the corrections.

On pages 106 and 107, an incorrect reference was cited. In the final paragraph on page 106, the last sentence should read: One study came to the conclusion that, although some minimum water application rates would achieve a certain objective, a marginally higher rate would not necessarily improve the situation (79). The figure caption for Figure 35 at the bottom of page 107 should read: FIGURE 35 NFPA 13, NFPA 15, and other International Water Application Rates (79).

The added reference is as follows:

79. Harris, K., “Water Application Rates for Fixed Fire Fighting Systems in Road Tunnels,” Proceedings from the Fourth International Symposium on Tunnel Safety and Security, A. Lönnermark and H. Ingason, Eds., Frankfurt am Main, Germany, Mar. 17–19, 2010.

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