Guidelines for Emergency Ventilation Smoke Control in Roadway Tunnels (2017)

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4Introduction The objective of this report is to improve the safety of high- way tunnels by developing methods and guidelines for emer- gency tunnel ventilation. The document provides guidance to the owners and agencies, law enforcement agencies, first responders, designers, and vendors in reference to emergency tunnel ventilation. It can also be used by state departments of transportation (DOTs) for implementing best practices within their tunnel operation program in order to improve public and emergency responder safety. To date, there is lim- ited experience and knowledge regarding effective practices for ventilating a significant roadway tunnel fire. This guide- line focuses on developing improved practices for road tunnel fire emergency ventilation which include but are not limited to, full transverse, partial transverse, and longitudinal type ventilation systems. The guideline considers tunnel geomet- rics such as tunnel altitude; physical dimensions (i.e., length, cross section); type of traffic flow (i.e., single or bi-directional flow); and fan utilization and placement. It also considers cargo types and quantities as they pertain to fire heat release rates (FHRRs) and ventilation requirements. The guideline determines the effects of ventilation on tunnel fires including fire size. It explores the interaction of firefighting and venti- lation system operation. The document addresses the prac- ticality of emergency tunnel ventilation system control and its application when other systems, such as fixed firefighting systems, are used. This work is part of a larger effort to develop best prac- tices that aim to lead to future development of tunnel design/ construction specifications and operations. Guidelines concerning construction are not included in the scope of this document. These guidelines also do not apply to the following facilities: 1. Rail tunnels 2. Mass transit tunnels and stations 3. Parking garages 4. Bus terminals 5. Truck terminals 6. Any other facility in which motor vehicles travel or are parked 1.1 Roadway Tunnels Emergency Ventilation—Current Industry Knowledge and Practice There is currently no in-depth guideline for emergency ven- tilation in roadway tunnels in the United States. The National Fire Protection Association (NFPA) produces a document, NFPA 502, that provides general requirements with further clarifications in its annex materials [1]. These guidelines are intended to utilize current industry knowledge to provide guiding principles for emergency ven- tilation with references to NFPA 502 and other standards. They are not intended to replace or supersede the NFPA 502 Standard. In case of any conflicts noted between the guide- lines and current or future editions of NFPA 502, the NFPA document takes precedence. One of the intents of this guideline is to help state high- way officials understand the risks and key decisions needed to design tunnel ventilation and fixed firefighting systems. While the process is quite complicated, the guidelines make an attempt to simplify the process to the roadmap in Figure 1.1. 1.2 Applicable Regulatory Standards and Guidelines 1.2.1 U.S. Standards, Synthesis Studies, and Guidelines NFPA 502, Standards for Road Tunnels, Bridges and Other Limited Access Highways (2014). This is the most referenced fire and life safety document for U.S. road tunnels [1]. The document defines fire and life safety requirements, including C h a p t e r 1

5 emergency ventilation for road tunnels. This standard covers limited access highways, bridges, road tunnels, and roadways beneath air-right structures and sets design requirements wher- ever applicable for the fire and life safety systems, structures, and emergency response procedures. This standard is updated every 3 years based on the most up-to-date information on tunnel fires, technological developments, and the experience of tunnel owners, agencies, law enforcement agencies, first responders, designers, and vendors. This document consists of the main standard and annex materials. The standard (main) part sets requirements for emergency ventilation and other fire and life safety systems. The annex of this document clari- fies requirements set in the main part. Annex I, titled “Tunnel Ventilation System Concepts,” discusses types of road tun- nel ventilation systems and Annex J, titled “Control of Road Tunnel Emergency Ventilation System,” discusses ventilation operational modes and controls requirements. Also, Annex A, titled “Explanatory Material,” provides a table of the relation- ship between vehicle types and heat release from a resulting fire. Most U.S. agencies and many international agencies rely on NFPA 502 for tunnel safety design. NCHRP Synthesis 415: Design Fires in Road Tunnels (2011) [3]. This document, produced by NCHRP(TRB), is a synthesis study of best national and international practices for fire and life safety and road tunnel emergency ventila- tion system design. It contains references to standards and guidelines developed around the world. The study discusses design fire scenarios in tunnels, full and small scale fire tests, modeling of the tunnel fires, main design fire parameters, and tenable environment conditions, while also providing a compilation of international tunnel ventilation standard requirements. This document includes a survey of national and international tunnel owners and agencies on road tunnel fires and best practices of tunnel fire management includ- ing fire frequency; consequences of fire incidents; severity of tunnel fires; existing practice of fire management; best design practice; maintenance, repair and rehabilitation of fire management systems; and a discussion on computer based training tools for operators to manage fire. In Chapter 9, it discusses the relationship between vehicle types, heat release, and venti lation requirements. In Chapter 13, the study dis- cusses the effects of ventilation on tunnel fires and fire size as well as fixed fire suppression systems (FFSS) and their impact on design fire size. The annex to the synthesis provides a comparison of national and international standard require- ments and additional information on past tunnel fires and fire tests. NCHRP Report 525: Volume 12, Making Transporta- tion Tunnels Safe and Secure (2006) [4]. While this report mostly addresses tunnel security issues, it provides numer- ous references to tunnel ventilation and control systems. This report provides a study about tunnel fire cases, potential hazards, countermeasures, and emergency system operation. The International Technology Scanning Program sponsored by AASHTO and the FHWA issued a report in 2006 titled, “Underground Transportation Systems in Europe: Safety, Operations, and Emergency Response,” with the objective of discovering what is being done internationally for under- ground transportation systems regarding safety, operations, and emergency response. This research project aimed to pro- vide safety and security guidelines for transportation tunnel owners and operators. To accomplish this task, a team of expe- rienced design engineers, builders, and operations personnel Figure 1.1. A roadmap for key decisions to design tunnel ventilation and fixed firefighting systems. What is the risk level of the tunnel? Does it require tunnel ventilation and fixed firefighting systems? (see Table 2.3 for a simplified example) What are the main design fire parameters that will influence the ventilation and suppression system design? (See Table 2.1 ) What type of ventilation system is needed? (See Figure 3.3 for a simplified decision making process) Is a fixed firefighting system needed along with ventilation, and what type is needed? (See Figure 2.1 for a simplified decision making process) How much water may be needed for the fixed fire suppression or fire control system? (See Figure B.2) How to control the tunnel ventilation? (See Figure 6.2 for a basic control concept)

6collaborated with safety and security experts to address the following questions: • What natural hazards and intentional threats do they face? • How would they be introduced? • What are the vulnerable areas of their tunnel? • How much of a disturbance would there be? • How can they avoid these hazards and threats? • How can they prepare themselves for this disturbance if it occurs? The report provides guidelines for protecting tunnels by minimizing the damage potential from extreme events so that they may be returned to full functionality in a relatively short period of time following damage. This report examines safety and security guidelines in identifying principal vul- nerabilities of tunnels to various hazards and threats. It also explores potential physical countermeasures, potential oper- ational countermeasures, and deployable integrated systems for emergency-related command, control, communications, and information. The report is organized into seven chapters and includes: • Hazard and Threats Analysis • Case Studies on Fire Events in Road and Railway Tunnels in Different Countries • Tunnel Structural and Vulnerabilities Analysis • Countermeasures and System Integration Transportation Research Record 883: Tunnel Ventilation, Lighting, and Operation (1982) [5]. This report is the only document on tunnel ventilation developed by TRB. It was developed by a group of engineers from Ministere des Trans- ports du Quebec, TLT-Babcock, Sverdrup & Parcel (Jacobs Engineering), and Fenco Consultants. This document includes best tunnel ventilation design practice and tunnel fan design issues. However, it does not address emergency ventilation and smoke control issues. Basis for Establishing Guides for Short-Term Exposure of the Public to Air Pollutants (1971) [6]. This report contains an evaluation of the relationship between exposure to a pol- lutant and its effect on the population. The report discusses the selection of short-term public air pollution exposure limits. Information presented in this report is outdated. NCHRP Project 20-07/Task 230, “Safety and Security in Roadway Tunnels” [7]. Prepared by Kathleen Almand from the Fire Protection Research Foundation in 2008, this report is a collection of papers and documents from the workshop held on November 29 and 30, 2007 at the National Academies Beck- man Center in Irvine, CA. The NCHRP project panel selected five international speakers to address the key research areas identified in the AASHTO Domestic Scan Program – Standing Committee on Highways. Three additional domestic speakers were invited to address the scan program, NCHRP Report 525/ TCRP Report 86, Vol. 12 [4]: Making Transportation Tunnels Safe and Secure, and a review of worldwide standards for fire safety in roadway tunnels. Participants developed the ideas for new research projects needed on Safety and Security in Road Tunnels. FHWA Reports No. FHWA-RD-78-184; 185; 186; 187— Aerodynamics and Air Quality Management of Highway Tunnels [8]. These reports were published in 1979 and pro- vide the basic principles and methods of tunnel aerodynamics calculations, vehicle emissions calculations, and ventilation controls. It presents concepts and detailed knowledge of the tunnel ventilation simulation software TUNVEN. FHWA Technical Manual for Design and Construction of Road Tunnels—Civil Elements FHWA -NHI-10-034 [9]. This comprehensive document provides general guidelines and recommendations for planning, designing, the construction of, structural rehabilitation, and repairing of civil elements for road tunnels including a brief coverage of fire safety and ventilation. FHWA Prevention and Control of Highway Tunnel Fires (1998) [10]. This guideline presents methods of preventing, responding to, and controlling fires in existing and future highway tunnels. ASHRAE Handbook of HVAC Applications, Chapter 15, “Enclosed Vehicular Facilities” (2015) [11]. This document summarizes international and national knowledge on tunnel ventilation and addresses ventilation under normal and fire emergency conditions. It is prepared by a group of experts in the ASHRAE and is updated every 4 years. Tunnel Operations, Maintenance, Inspection, and Evalu- ation (TOMIE) Manual (2015) [12]. This manual provides guidelines on tunnel operations, maintenance, inspection, and evaluation that help ensure tunnels remain in safe con- dition and continue to provide reliable levels of service. To help safeguard tunnels and ensure reliable levels of service on public roads, the FHWA developed the National Tunnel Inspection Standards (NTIS); the Tunnel Operations Main- tenance Inspection and Evaluation (TOMIE) Manual; and the Specifications for National Tunnel Inventory (SNTI). The NTIS contains the regulatory requirements for the tunnel inventory and inspection program; the TOMIE Manual and the SNTI have been incorporated into the NTIS to expand upon these requirements. The TOMIE provides uniform and con- sistent guidance on the operation, maintenance, inspection, and evaluation of tunnels. 1.2.2 International Standards and Guidelines The NFPA 502 Standard is developed with the support of the tunnel engineering community around the world by synthesizing the best international practices. The most known

7 international organization that sets requirements for emer- gency road tunnel ventilation is the World Road Association (PIARC), which has working groups representing the inter- national practice. In addition, there are standards and guide- lines developed by the European Union (EU), Australia, and many other countries that have numerous road tunnels and have over a century of experience in road tunnel ventilation systems. The EU defines only the minimum standard in a very general way. Various European countries, such as Switzerland, Austria, Germany, and Norway have their own standards which provide guidelines for tunnel ventilation operation. For example, in Switzerland the Federal Roads Office (FEDRO/ ASTRA) is responsible for national roads and specifies safety requirements that comply with EU directive 2004/54/EC. A series of national guidelines specify higher requirements than those in the EU directive. They clearly identify when a risk analysis has to be carried out when there are differences between the national standards and the guidelines. Most of the risk analysis models require computational fluid dynam- ics (CFD) analysis for ventilation and egress modeling to be performed. PIARC has established several working groups to address tunnel safety, fire, and ventilation issues. Representatives from many countries around the world are participants of those working groups and have developed a number of interna- tional documents described herein. PIARC Integrated Approach to Road Tunnel Safety (2007) [13]. This report was prepared by Working Group 2, “Man- agement of Tunnel Safety” of the Technical Committee C3.3 on Road Tunnel Operation of the World Road Association PIARC. This report proposes an integrated approach to road tunnel safety, which has been developed in cooperation with the European research projects SafeT and UPTUN. The report summarizes general principles and current perspectives on road tunnel safety and includes practical tunnel project expe- rience. The key elements for an integrated approach to road tunnel safety are the following: • Safety level criteria (regulations and recommendations); • Infrastructure and operational measures for tunnel safety; • Socio-economic and cost-benefit criteria; • Safety assessment techniques (safety analysis and safety evaluation); • Road tunnel usage; • Stage of the tunnel life (planning, design, construction; com- missioning; operation, refurbishment or upgrading); • Operating experience; and • Tunnel system condition. A schematic representation of the integrated approach to the safety of new and in-service tunnels is shown in Figure 1.2. Integrated safety for tunnels can be presented as a ‘safety cir- cle’ (see Figure 1.3). It can be inefficient to focus on improving the safety performance of only one element in the sequence without considering the safety performance of the other elements. Figure 1.2. Schematic representation of the integrated approach to safety [13].

8PIARC Fire and Smoke Control in Road Tunnels (1999) [14]. This book provides general guidelines and functional requirements for fire and smoke control in road tunnels. Recently PIARC issued the report Fixed Fire Fighting Systems in Road Tunnels: Current Practices and Recommendations. PIARC Risk Analysis for Road Tunnels (2008) [2]. This report has been prepared by Working Group 2 “Manage- ment of Road Tunnel Safety” of the Technical Committee C3.3 Road Tunnel Operation of the World Road Associa- tion PIARC. Risk analysis is an important tool which can be used to help improve and optimize the safety of road tunnels. Although the likelihood of major tunnel incidents is low, the consequences can be severe in terms of casualties, damage to tunnel structures and equipment, and the impact on the transport economy. For example, the fire in the Mont Blanc tunnel in 1999 claimed 39 lives, led to its closure for 3 years, and incurred economic losses of about 300 million euros. Risk analysis is now explicitly required by the European Directive 2004/54/EC in the minimum safety requirements for road tunnels in the Trans-European Road Network. Risk analysis involves the identification of hazards and the estimation of the probability and consequences of each hazard. The risks are determined from the product of their probability and conse- quences. Once analyzed, the risks need to be evaluated and, if unacceptable, need to be treated (risk mitigation by additional safety measures). A wide range of qualitative and quantita- tive methods are available. The report presents two families of suitable approaches for the risk assessment of road tunnels: • A scenario-based approach, which analyzes a defined set of relevant scenarios in terms of frequency and/or con- sequences; the risk assessment is done separately for each individual scenario. • A system-based approach, which investigates an overall system in an integrated process, including all relevant sce- narios influencing the risk of the tunnel, thus obtaining risk values for the whole system. For the purpose of risk evaluation, the procedure to deter- mine whether the tolerable risk has been achieved, several dif- ferent types of risk criteria are available. These criteria include expert judgement; scenario related criteria (e.g., threshold val- ues for scenario probabilities or escape time to a point of safety); individual risk (e.g., probability of death per year for a specific person exposed to a risk); and societal risk (e.g., expected num- ber of fatalities in the tunnel per year or a frequency-number of fatalities [FN] curve). The choice of which criteria to apply depends on the application. Quantitative risk criteria can be adopted as absolute threshold values (e.g., a system is safe if the relevant risk value of the system is lower than the defined threshold value) or for relative comparisons (e.g., compari- son of different safety measures or comparison of a system to a “safe” reference system). The meaning of risk analysis and its characteristics can be summarized as follows: • Risk analysis is a systematic approach to analyze sequences and interrelations in potential incidents or accidents, hereby identifying weak points in the system and recog- nizing possible improvement measures, such as ventilation improvements; • The term “Risk Analysis” covers a large family of different approaches, methods and complex models combining various methods for specific tasks; • Risk analysis can include a quantification of risks which can be used as the basis of a performance-based approach to safety; • A general basic principle of all kinds of risk analysis for road tunnels should be a holistic approach including infra- structure, vehicles, operation and—last but not least— users (see Figure 1.4). All the methods exhibit specific advantages and disadvan- tages, but none can claim to be the most suitable in practical use in the context of road tunnel safety management. The most appropriate approach should be selected by consider- ing the respective advantages and disadvantages in the con- text of a specific situation. The selection should reflect the nature of the problem, the required depth of assessment and the available resources. It has to be taken into account that quantitative methods (e.g., simulations or statistical analysis) are normally more complex and therefore imply more effort for the analysis than qualitative methods (e.g., expert judg- ments). Furthermore, quantitative methods require specific quantitative input data which may not be available or suffi- cient, or may not be of the quality required. In addition, it has to be considered that methods cannot be chosen arbitrarily; certain risk evaluation and risk analysis methods have to be used together. Figure 1.3. Integrated safety circle for tunnels [13].

9 Figure 1.5 illustrates an example of a system-based approach which results in risk values for an overall system to be esti- mated. The risk assessment is performed for the whole tun- nel system investigated on the basis of the risk values of the system (expected value, FN curve). A typical application of a system-based approach might be the evaluation of different additional safety measures including ventilation in terms of their influence on risk. Another method is a scenario-based approach for which a set of relevant scenarios is defined, the probability of each scenario is estimated and the possible resulting consequences are analyzed. The risk assessment is done separately for each single scenario on the basis of its characteristic indicators (e.g., frequency of scenario, parameters describing effects and consequences of scenario). Experience shows that the question of risk evaluation and the definition of what level of risk is acceptable is a significant and debatable part of risk management. In the United States, risk evaluation is often used for existing tunnels ventilation and other fire life safety systems upgrades. The PIARC report presents the following recommendations for the practical use of risk analysis: • Be aware that whatever method you choose, you are always using a model which is a more or less major simplification of the real conditions. The method can never predict the course of a real event but helps you to make decisions on a sound and comparable basis; • Select the best method available for a specific problem; • When selecting a method for a risk analysis, you should also consider how to evaluate the results since the method of risk analysis and the strategy of risk evaluation are not independent; • Whenever possible, use specific data for quantitative meth- ods. If specific data is unavailable, at least check the origin of the data you intend to use (are the conditions relating to infrastructure, traffic, etc. similar to your situation?). Be aware that specific features may be included in a risk model that are not valid for your tunnel; • Risk analysis should only be performed by experts with sufficient experience and understanding of the methods they use; • Be aware that the result of a quantitative risk analysis must be interpreted as an order of magnitude and not as a precise number. Risk models inevitably deliver fuzzy results, so risk evaluation by relative comparison (e.g., of various safety measures or of an existing state to a reference state of a tun- nel) may improve the robustness of conclusions drawn. Figure 1.4. Holistic approach to risk analysis [2]. Figure 1.5. Example of system-based approach to risk analysis [2].

10 The procedure for a risk analysis can be divided into the following three steps: • Hazard identification: Systematic process to identify and structure all relevant hazards, and to analyze their correlat- ing effects; • Probability analysis: Determination of the probabilities of relevant events/scenarios; • Consequence analysis: Investigation of consequences of relevant scenarios. The simplified flowchart in Figure 1.6 illustrates the main steps of the risk assessment process. It shows the main typi- cal components of the risk assessment process only; more detailed diagrams, supplementary components, and addi- tional mutual links may be needed when analyzing the safety of a particular tunnel. The concept of tunnel safety is schematically shown in Fig- ure 1.7. Although life safety must always be of paramount importance, the severe operational risks presented by a long term tunnel closure cannot be underestimated. Risk assessments are regularly used to determine how to prioritize limited resources (such as money and expertise) in the systematic improvement of some aspect of safety per- formance, such as ventilation systems upgrades. “Unfortu- nately, the techniques described as ‘risk analysis’ are often either mathematically flawed or applied so poorly that the results are, at best, meaningless and, at worst, highly destruc- tive to sound decision making” [2] resulting in untenable environment, large scale loss of life and structural compro- mises. Without adherence to the fundamental mathematical principles of “risk analysis” by practitioners almost any out- come is possible—by accident or by design. The seriousness of this situation is compounded by the fact that there is a temptation to use these techniques as a substitute for profes- sional judgement—and not limit its use as a tool to assist in the decision making process to upgrade existing tunnels. Understanding the limitations of risk analysis is fundamen- tal to using its tools and techniques to effectively understand and manage risk. There is a shortage of data for such risk analysis to be conducted in many tunnel contexts. This lack of data makes proving the results are wrong, or even discover- ing the nature of the errors, extremely difficult—except at the conceptual level [2]. PIARC Road Tunnels: Operational Strategies for Emer- gency Ventilation (2011) [15]. This study provides guidelines for ventilation systems, emergency ventilation control and operation. PIARC Systems and Equipment for Fire and Smoke Con- trol in Road Tunnels (2007) [16]. This study complements the 1999 PIARC report “Fire and Smoke Control in Road Tunnels” and provides in-depth details of fire specific equip- ment and emergency operation issues. Chapter 1 discusses the basic principles of smoke and heat development at the beginning of a fire, including the role of the ventilation system during the self-evacuation and Figure 1.6. Flowchart of the procedure for risk assessment [2].

11 firefighting phases. Chapter 2 discusses tunnel fire safety con- cepts including safety during the design, construction, opera- tion, and maintenance phases. It discusses risk analysis and introduces the “ALARP” approach, which aims to ensure that risks are “As Low As Reasonably Practicable.” The key opera- tive word is “reasonably.” The interpretation of “reasonably practicable” inevitably depends on the point of view of the person making the judgment (operator, user, lawyer, etc.). Such an approach is limited by the fact that a cost/benefit analysis will never be positive if comparing investments in tunnel with other investments in the open air. Chapter 3 discusses lessons learned from recent tunnel fires including the Mont Blanc, Tauern, and the St. Gotthard Tunnel fires. Chapter 4 discusses different types of ventilation systems and ventilation equipment. Chapter 5 discusses emergency exit and escape route design and cross passage configurations. Chapter 6 is on fire equipment including fire detection and fire suppression. Chapter 7 addresses issues related to the structural resistance of the tunnel to fire. Chapter 8 is on the operations and control including preventive maintenance, inspection, and testing. PIARC Fixed Fire Fighting Systems in Road Tunnels: Current Practices and Recommendations [17]. The purpose of this report is to provide decision makers and designers with information to assist them with their understanding of the parameters of Fixed Firefighting Systems (FFFS), and to provide guidance on whether or not to include FFFS in their road tunnels. The report looks at international experi- ence based on current installations, test programs, and real life incidents. In some countries, risk and cost-benefit analy- ses are used to consider the application of FFFS as a mea- sure to assist in making infrastructure both safer and more durable in the event of an incident. However, for various political, economic, technical, and social reasons, it is recog- nized that they may not be the most appropriate measure to adopt in all circumstances. These reasons can include where a road tunnel has a dedicated fire service to provide a similar response in a timely manner, where a government direc- tive asserts that FFFS will not be applied in that particular country’s tunnels, or where FFFS will not be maintained and operated to the degree of reliability and availability required. Where FFFS are installed, it is essential that they be correctly designed, installed, integrated, commissioned, maintained, tested, and operated with a high level of reli- ability and availability, so that the system is available for use as required. Design and Figure 1.7. Tunnel safety concept.

12 The role of FFFS for road tunnels is to provide facilities for tunnel owners and operators to assist with the early suppres- sion and subsequent management of fires. In this manner, the consequences of a fire event to tunnel users, the tunnel infrastructure, and the societal impact due to the disruption to the wider road network can be mitigated. Their installation enables the fixed infrastructure within a tunnel to address fires more quickly and more easily than if incident respond- ers had to provide and deliver alternate systems to the fire site to respond to the event. As FFFS are part of the tunnel infrastructure, they allow fire control to be initiated from a remote location automati- cally, semi-automatically, or manually. This provides advan- tages in that FFFS allow: • Fires to be addressed in a timely manner, even before the fire brigade arrives at the incident site; • Delivery of sufficient water to the fire site such that control or suppression of a fire occurs before the fire develops into a full-scale conflagration; • The fire brigade to manage the fire incident without putting themselves at risk by being in the near vicinity of a fire; and • The fire brigade to fully extinguish the fire once it has been suppressed, if required. Properly designed, installed, integrated, commissioned, maintained, tested, and operated FFFS will: • Provide early suppression and control of a fire event; • Retard the fire growth rate, inhibiting the combustion pro- cess and reducing the heat output; • Remove heat from the environs of the fire by cooling the surrounding area during an incident; • Limit the potential for fire to spread between vehicles; • Extend the available escape time for tunnel users; • Improve overall tenability for firefighters, enabling them to respond to the event more effectively; • Reduce the likelihood and extent of structural damage; • Limit the severity and extent of damage to tunnel systems and equipment; • Allow the asset to return to service in a shorter period of time following a fire; and • Return the external road network to full integrity in a shorter period of time following a fire. When deciding whether or not to install any type of FFFS, the following must be examined: • The functions and roles of FFFS in the safety concept; • Life safety; • Asset protection and the protection required to assure the availability of the transport link; • Flexibility for additional traffic regimes such as Dangerous Goods Vehicles (DGVs); • Firefighting response; • The ability to adequately operate and maintain the system, including the roles, positions, and responsibilities of the stakeholders; • The installation capital cost and/or life cycle cost, as well as the cost-benefit from installing FFFS; • System reliability and redundancy; and • Sustainability, as this may also be a factor in the decision. The report discusses fire modelling and specifically com- putational fluid dynamics (CFD) to accurately model many aspects of tunnel fire safety. There have been several full-scale test programs that have been used to perform comparisons of various aspects for CFD modeling. The challenges are in the areas of pyrolysis, combustion, and spray modeling including wall impingement. The phenomenon of pyrolysis is very com- plex. However, approximate models can be applied in some scenarios. This corresponds to the highest uncertainty in CFD modeling of FFFS. Obtaining accurate solutions is much more challenging than gas-phase calculations for tunnels because the gas and liquid phases must be treated separately and a number of sub-models, such as those accounting for inter-phase mass, momentum, and heat transfer, have to be carefully selected and verified. In summary, CFD models with FFFS and a prescribed HRR can be used with a high degree of confidence to predict tem- peratures, radiative heat flux, and smoke behavior in regions remote from the immediate fire. Methods exist to predict the interaction of FFFS with the HRR. However, these methods involve more complex physics, a greater range of length scales, and are influenced by uncertainty in the actual fire geometry. As such, the prediction of HRR and combustion product yields using CFD is an evolving area of practice. Other International Documents including European and United Nations (UN) documents which are the result of international projects sponsored by the European Union to address tunnel safety issues after tragic tunnel fire events include the following: • European Thematic Network Fire in Tunnels (FIT) Report (2005) [18]. FIT provided a European platform for the dis- semination and exchange of up-to-date knowledge and research on fire in tunnels. FIT consisted of 33 members from 12 European countries. The aim was to optimize research efforts and to release recommendations on design fires for tunnels. Additionally, FIT had an objective to develop a European consensus for fire safety design on the basis of existing national regulations, guidelines, codes of practice, and safety requirements. The objective included defining the best practices for tunnel authorities and fire

13 emergency services on prevention and training, accident management, and fire emergency operations. Among other reports, it provided the best practices for fire response management. • UN Recommendations on Safety in Road Tunnels, United Nations Economic Commission for Europe (2001) [19]. Tunnel safety factors are summarized in four groups (road users, operation, infrastructure, vehicles), and safety measures and guidelines are provided. • UK Highways Agency BD78—Design of Road Tunnels (1999) [20]. This document established criteria for the evaluation of basic tunnel ventilation and fire and life safety systems design. It provided guidelines on fire size, smoke stratifica- tion, interaction between firefighting operation and ven- tilation, and the applicability of a fire suppression system. Several recently developed national Austrian, Australian, Brazilian, and Norwegian guidelines were reviewed and include the following: • Australasian Fire Authorities Council (AFAC), Fire Safety Guidelines for Road Tunnels (2001) [21]. This document provides information, guidelines, and requirements for tunnels and tunnel fire safety. • Austroads (an association of Australasian road transport and traffic agencies) Guide to Road Tunnels (2010) [22]. This doc- ument provides general guidelines and functional require- ments for fire safety and ventilation in road tunnels. • Australian Standard AS 4825-2011 Tunnel Fire Safety [23]. This document is an informative standard (guidance) which provides a performance-based framework to establish the required level of safety. This standard does not set prescriptive requirements, but is based on a risk manage- ment approach. It sets requirements for smoke analysis, smoke hazard management for evacuation, and perfor- mance requirements for tenability criteria with reference to the SFPE Handbook of Fire Protection Engineering. It provides references to international standards such as NFPA 502. • Norwegian Public Roads Administration, Road Tunnel (Design Manual, 2004) [24]. This document includes a calculation model for ventilation. • Austrian Guidelines RVS 09.01.45, 2006 “Constructional Fire Protection in Transportation Buildings for Roads”; RVS 09.02.31, 2014 “Tunnel Equipment, Ventilation, Basic Principles”; and RVS 09.02.41, 2014 “Tunnel Equip- ment, Fixed Fire Extinguishing Systems”. • Brazilian Standards on Tunnel Life Safety: – Fire protection in Tunnels—ABNT NBR 15661:2012. The standard specifies the safety requirements to fire prevention and protection in tunnels, with passengers and or cargo transportation. – Tunnel Fire Safety Systems—Signaling and Emergency Warning ABNT NBR 15981:201. The standard specifies requirements in signaling and emergency warning sys- tems related to fire prevention and protection of tunnels users, cargo transportation and patrimony. – Tunnel Fire Safety Systems—Tests, Commissioning and Inspections – ABNT NBR 15775:2014. The standard specifies the requirements for testing, commissioning, and inspecting electrical and mechanical equipment, operation systems, measurement devices, fire detec- tion and firefighting systems and civil constructions related to the fire prevention and protection of users and cargo. 1.2.3 Other Publications for Emergency Ventilation Smoke Control in Roadway Tunnels Other U.S. and international reports and references on tunnel fire safety reviewed for development of the guidelines include the following: Massachusetts Highway Department Memorial Tunnel Fire Ventilation Test Program (MTFVTP)—Test Report (1995) [25]. This report summarizes the full-scale fire tests conducted with various types and configurations of tunnel ventilation systems and foam suppression systems. This pro- gram was financed by the Federal Highway Administration and the Commonwealth of Massachusetts for the Boston Central Artery Tunnel project. The experiments were per- formed in an abandoned 854 m (2,800 ft) long road tunnel located in West Virginia. About 91 fire tests were performed with diesel oil pool fires. The obtained heat release rates var- ied from 10 MW (34 MBtu/hr) for a 4.5 m2 (48.4 ft2) area of diesel to 100 MW (341 MBtu/hr) for a 44.4 m2 (478 ft2) area of diesel. 1,450 devices were installed in the tunnel, pro- viding about 4 million points of data per experiment. The Memorial Tunnel program performed tests with fire sizes of 10, 20, 50, and 100 MW (34, 68, 172, and 341 MBtu/hr). These tests were performed with various ventilation systems including: • Full Transverse Ventilation—Air is uniformly supplied and exhausted throughout the entire length of a tunnel or tunnel section. • Partial Transverse Ventilation—Either supply air or exhaust air, but not both, is uniformly delivered or extracted through- out the entire length of a tunnel. • Partial Transverse with Single Point Extraction—A series of large, normally-closed exhaust ports distributed over the length of the tunnel to extract smoke at a point closest to the fire.

14 • Partial Transverse with Oversized Exhaust Ports—Normally- closed exhaust ports that automatically open in a fire emergency. • Natural Ventilation. • Longitudinal Ventilation with Jet Fans. The report concluded that a longitudinal ventilation system employing jet fans is highly effective in managing the direction of the spread of smoke for fire sizes up to 100 MW (341 MBtu/ hr) in a 3.2 percent grade tunnel. The throttling effect of the fire needs to be taken into account in the design of a jet fan longitudinal ventilation system. Jet fans that were located 51.8 m (170 ft) downstream of the fire were subjected to the following temperatures for the tested fire sizes: • 204°C (400°F)—20 MW (68 MBtu/hr) fire • 332°C (630°F)—50 MW (170 MBtu/hr) fire • 677°C (1250°F)—100 MW (341 MBtu/hr) fire Air velocities of 2.54 m/sec to 2.95 m/sec (500 fpm to 580 fpm) were sufficient to preclude the backlayering of smoke (movement of smoke and hot gases in the opposite direction of intended ventilation airflow in the tunnel roadway) in the Memorial Tunnel for fire tests ranging in size from 10 MW to 100 MW (34 MBtu/hr to 341 MBtu/hr). Single-zone, balanced, full transverse ventilation systems that were operated at 0.155 m3/s/lane meter (100 ft3/min/lane foot) were ineffective in the management of smoke and heated gases for fires of 20 MW (68 MBtu/hr) and larger. Single-zone, unbalanced, full transverse ventilation systems generated some longitudinal airflow in the roadway. The result of this longitu- dinal airflow was to offset some of the effects of buoyancy for a 20 MW fire (68 MBtu/hr). The effectiveness of unbalanced, full transverse ventilation systems is sensitive to the fire location since there is no control over the airflow direction. The two-zone (multi-zone) transverse ventilation system that was tested in the MTFVTP provided control over the direction and magnitude of the longitudinal airflow. Airflow rates of 0.155 m3/s/lane meter (100 ft3/min/lane foot) con- tained high temperatures from a 20 MW (68 MBtu/hr) fire within 30 m (100 ft) of the fire in the lower elevations of the roadway and smoke within 60 m (200 ft). The spread of hot gases and smoke was significantly greater with a longer fan response time. Hot smoke layers were observed to spread very quickly, from 490 m to 580 m (1600 ft to 1900 ft), during the initial two minutes of a fire. Natural ven- tilation resulted in the extensive spread of smoke and heated gases upgrade of the fire, but relatively clear conditions existed downgrade of the fire. The spread of smoke and heated gases during a 50 MW (171 MBtu/hr) fire was considerably greater than for a 20 MW (68 MBtu/hr) fire. The depth of the smoke layer increased with fire size. For the tests, a flat ceiling was built in the tunnel at a lower height than the arched tunnel roof. A significant difference was observed between smoke spread with the ceiling removed (arched tunnel roof) and with the ceiling in place. The smoke and hot gas layer migrating along the arched tunnel roof did not descend into the roadways as quickly as in the tests that were conducted with the ceiling in place. Therefore, the time for the smoke layer to descend to a point where it poses an immediate life safety threat is dependent on the fire size and tunnel geometry, specifically tunnel height. In the Memorial Tunnel, smoke traveled between 290 m and 365 m (950 ft and 1200 ft) along the arched tunnel roof before cooling and descending towards the roadway. The loss of visibility caused by the movement of smoke occurs before a temperature that is high enough to be debilitating. In all tests, exposure to high levels of carbon monoxide was never more critical than expo- sure to smoke or temperature. The effectiveness of the aqueous film forming foam (AFFF) suppression system that was tested was not diminished by high-velocity longitudinal airflow [4 m/sec (787 fpm)]. The time taken for the suppression system to extinguish the fire, with the sprinkler heads located at the ceiling, ranged from 5–75 seconds. The maximum temperatures experienced at the inlet to the central fans that were located closest to the fire [approxi- mately 213 m (700 ft) from the fire] were as follows: • 107°C (225°F)—20 MW (68 MBtu/hr) fire • 124°C (255°F)—50 MW (171 MBtu/hr) fire • 163°C (325°F)—100 MW (341 MBtu/hr) fire In a road tunnel, smoke management necessitates either direct extraction at the fire location or the generation of a lon- gitudinal velocity in the tunnel that is capable of transporting the smoke and heated gases in the desired direction to a point of extraction or discharge from the tunnel. Without a smoke management system, the direction and rate of movement of the smoke and heated gases are determined by fire size, tunnel grade (if any), pre-fire conditions, and external meteorological conditions. The program report shows that balanced, full transverse ventilation is ineffective at controlling smoke and tempera- tures when fires are above 20 MW (68 MBtu/hr). Being able to effectively control temperatures when fires are below 20 MW (68 MBtu/hr) depends on the fire location. However, if the transverse ventilation system is modified to be a two-zone system, it can have the capability to control temperature and smoke for a 20 MW (68 MBtu/hr) fire positioned at different locations along the length of the tunnel. SOLIT2 Safety of Life in Tunnels, Annex 3 Engineering Guidance for Fixed Fire Fighting Systems in Tunnels (2012) [26]. The Safety of Life in Tunnels project was sponsored by the German Government. Over 50 large scale tests were performed.

15 Extrapolating from free-burn data, the researchers calculated that the fire load of a heavy goods vehicle with idle pallets could grow to 180 MW (614 MBtu/hr). Water mist systems reduced the heat release rate to 20-50 MW (68-171 MBtu/hr). SOLIT2 is the engineering guidance for a comprehensive evaluation of tunnels with FFFS using the example of water-based FFFS. Requirements and Verification Methods of Tunnel Safety and Design, SP Technical Research Institute of Sweden (2012) [27]. This report discusses the fundamentals of performance- based fire safety design in tunnels. Tunnel Engineering Handbook (1996) [28] The Handbook of Tunnel Fire Safety (2005) [29] Tunnel Fire Dynamics (2014) [30]. This book provides an overview of the dynamics and developments of fires in tunnels. It provides guidelines for calculation of important design parameters and referred to in the following chapters.