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Design Fires in Road Tunnels (2011)

Chapter: Chapter Ten - Compilation of Design Guidance, Standards, and Regulations

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Suggested Citation:"Chapter Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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 Ten - Compilation of Design Guidance, Standards, and Regulations." 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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79 Design guidance, regulations, standards, and reports developed around the world are shown in Table 25. This table was compiled from a review of different literature sources. PIARC, NFPA, the United Nations (UN), European Union (EU) requirements and other international guidelines are well recognized around the world. EU Directive 2004/54/EC aims at ensuring a minimum level of safety for road users in tunnels in the trans-European network. The U.K. Design Manual for Roads and Bridges (BD 78/99) covers the procedures required for the design of new and refurbished road tunnels (53). In addition, it provides guid- ance for the necessary equipment and the required operational and maintenance systems. PIARC is currently developing new recommendations on tunnel fire safety design that are sched- uled to be released in 2011. Traffic density and tunnel length is determined in the defi- nition of the safety measures of many countries. This allows several countries to define tunnel categories (United Kingdom, Austria, Norway, France, Japan, and United States). • The passenger exit and the emergency access for rescue staff generally are covered by national regulations. Inter- distances between escape routes vary from 100 to 400 m (328.1 to 1,312.3 ft); the European directive defines a maximum distance of 500 m (1,640.4 ft). NFPA 502 does not allow for emergency exits to be spaced more than 300 m (984.3 ft) apart, with spacing justified by engi- neering analysis. The spacing requirement for shelters is not as frequent; however, these must have an access way connected to the outside (France, European directive). • In many countries, the drainage of flammable liq- uid appears to be a well-defined safety element, with civil engineering and geometry arrangements specially adapted. • For safety equipment, ventilation and smoke control during a fire are considered fundamental and in most countries are defined by detailed guidelines. From these guidelines the following can be summarized: Mechan- ical ventilation is a necessity for long tunnels. The required air volumes and velocities or the objectives must be met according to the selected design fire (per- formance-based approach). Requirements are speci- fied to prevent smoke penetrating emergency exits and rescue access. • The tunnel, the emergency exits, and rescue access lighting are defined by a minimal assisted luminance level. • The requirements for traffic signage, both outside and within the tunnel, and signage for pedestrian exit and rescue, are generally clearly outlined in the guidelines. • Communication and alarm systems, such as emergency telephones and alarm push-buttons are generally con- sidered to be the minimum basic elements. However, the required spacing varies from 50 to 250 m (164 to 820.2 ft); the value of 150 m (492.1 ft) is specified by the European directive. Requirements focused on the auto- matic alarms on equipment, automatic incident detection, fire or smoke detection, and on radio rebroadcast. The installation of loudspeakers within the tunnel itself is not common, but requested in the evacuation facilities or shelters for the users. • For traffic regulation and monitoring equipment, mea- surements must be adapted to the surveillance level of the tunnel. Guidelines were primarily established to allow for quick detection of the traffic incidents, such as traffic speed, density measurement, video control, and the means for a quick closure of the tunnel. The thermographic por- tal detectors that locate abnormally hot trucks before they enter the tunnel are never prescribed. • The requirements for an emergency power supply for the safety equipment are generally well-specified. • Regarding fire fighting, the distribution of fire extinguish- ers and fire hydrants of sufficient capacity throughout the tunnel, as well as the presence of a water network and fire hydrants of sufficient capacity, are prescriptive. Sev- eral countries place hydrants every 150 and 250 m (492.1 and 820.2 ft), whereas the European directive notes the maximum value of 500 m (1,640.4 ft). The installation of a fixed fire suppression system is not imposed in any regulation. The structure and equipment require ample fire require- ments. The structural resistance requirements vary from very prescriptive requirements (Germany) to more or less performance-based criteria (France, Austria, and Norway). The criteria are given in terms of duration and specified fire curves or HRRs. Documented calculations are required in all guidelines. Equipment resistance to heat is specified by heat reaction or resistance. The European directive defines these requirements much less precisely than many national guidelines. The following gaps have been noted CHAPTER TEN COMPILATION OF DESIGN GUIDANCE, STANDARDS, AND REGULATIONS

80 Country Title ID Type Publisher/Year 1 U.S. NFPA 502 NFPA Standard 2008 and proposal for 2011 edition 2 U.S. Prevention and Control of Highway Tunnel Fires U.S.DOT, FHWA Report FHWA.dot.gov (2002) 3 U.S. Underground Transportation Systems in Europe U.S.DOT, FHWA, AASHTO Report NCHRP 06.2006 4 U.S. Making Transportation Tunnels Safe and Secure TCRP, NCHRP Report TCRP Report 86/NCHRP Report 525 5 U.S. Enclosed Vehicular Facilities ASHRAE Handbook 2011 (every 4 years) 6 UN Recommendations of the Group of Experts on Safety in Road Tunnels UN TRANS/AC.7.9 Report Economic and Social Council, Inland Transport Committee (2001) 7 Australia Fire Safety Guideline for Road Tunnels AFAC Guideline Australian Fire Authority Council (2001) 8 Austria Guidelines and Regulations for Road Tunnel Design RVS, IBS Guideline Transportation and Road Research Association (2001) 9 Austria Guidance document A-13 for fire safety in road tunnels ÖBFV Code (regulation) Austrian fire department. document based on European Directive 2004AEA4/EC 10 France Inter-ministry circular no. 2000-63 of 25 August 2000 relating to the safety of tunnels in the national highways network Circular 2000t63A2; CETU, CNPP; INERIS Government circular Ministry for intra- structure, transport, spatial planning tourism, and the sea (2000) 11 France Inter-ministerial circular no.2000-82 of 30 November 2000 concerning the regulation of traffic with dangerous goods in road tunnels of the national network Circ2000-82N2 Governmental circular Ministry for intra- structure, transport, spatial planning tourism, and the sea (2000) 12 France Law no. 2002-3 of 3 January 2002 relative to safety of infrastructures and transport systems, etc. Law2002-J2 Law Law 2002-3, art. 2 13 France Risk studies for road tunnels: Guide to methodology ESD Guidelines Guide 2002 TABLE 25 DESIGN GUIDANCE, REGULATIONS, STANDARDS, AND REPORTS DEVELOPED AROUND THE WORLD (continued on next page)

81 14 Germany Guidelines for equipment and operation of road tunnels RABT, DMT, SOLIT, STUVA, VdS, VFDB Guidelines Road and Transportation Research Association 15 Germany ZTV Additional Technical Conditions for the Construction of Road Tunnels - Part 1 Closed Construction - Part 2 Open Construction ZTV–Tunnel Technical addendum 1995 1999 16 Italy Tunnel lighting UNI–Milano U29000240 Guidelines July 2003 17 Italy Circular 6 Dec. 1999. Safety of Traffic in Road Tunnels with Particular Reference to Vehicles Transporting Dangerous Materials Circular 06.12.1999 Governmental circular 1999 18 Italy Functional and geometrical standard for construction of roads Ministry of Infrastructure and Transport Ministerial decree General Inspectorate for Traffic and Road Safety 19 Japan Design Principles, Vol. 3 (Tunnel) Part (4) (Tunnel Safety facilities) — Corporation guideline Japan Highway Public Corporation (1998) 20 Japan Installation Standards for Road Tunnel Emergency Facilities Safety standards Japan Highway Public Corporation 21 Korea National Fire Safety Codes NFSC Code (regulation) Korea National Emergency Management Agency 22 Korea Guideline for Installation of Safety Facility in Road Tunnels GIST Guideline Ministry of Construction & Transportation (2004) 23 Netherlands Technical standards for the provisions and installations RWS curves Rijkswaterstaat; TNO (UPTUN) Guideline Dutch Ministry of Transport and National Regulator 24 Norway Norwegian design guide, roads, tunnels Public Roads Administration, Directorate of Public Roads Guideline/ manual issued by public authority Handbook 021 25 Norway Road Tunnels Staten Vegvesen (SINTEF NBL) Government guideline Norwegian Public Roads Administration, Directorate of Public Roads (2004) 26 Norway Risk analysis of fire in road tunnels (Norwegian Council for Guideline for a Norwegian Issued by the Standardisation TABLE 25 (continued) (continued on next page)

82 Construction Standards) Standard Council (2000) 27 Russia Construction Rules and Regulations (SNIP) # 32-04-97 “Railway and Road Tunnels” SNIP Guideline State Construction Committee (GOSSTROI) 28 Spain Manual for the Design, Construction and Operation of Tunnels IOS-98 Manuals are effectively standards Nov. 1998 29 Spain Road Instruction, Norm, Alignment IC Norma 3.1 Dec. 1999 30 Spain Road Instruction, Norm, Vertical signals IC Norma 8.1 Dec. 1999 31 Sweden Tunnel 2004 Tunnel 2004 Guideline Swedish National Road Administration (2004) 32 Sweden Comparison and Review of Safety Design Guidelines for Road Tunnels SP Report 2007:08 Report SP Swedish National Testing and Research Institute Report 2007 33 Sweden Model Scale Tunnel Fire Tests: Sprinkler SP Report 2006:56 Report SP Swedish National Testing and Research Institute Brandforskprojekt 406- 021 34 Switzerland Guidelines for the Design of Road Tunnels. ASTRA (Swiss Federal Roads Office) Guidelines by the federal roads office 2005 (updated) 35 Switzerland Ventilation of Road Tunnels, Selection of System, Design and Operation ASTRA (Swiss Federal Roads Office) Guidelines Federal roads office (2004) 36 UK Design Manual for Roads and Bridges, Vol. 2: Highway Structure Design Section 2, Part 9, BD 78/99: Design of Road Tunnels BD 78/99 Guideline and requirements The Highway Agency (1999) 37 EU Directive 2004/54/EC of the European parliament and the council Directive 2004/54/EC Code (regulation) European parliament and the council (2004) 38 EU European Tunnel Research Program UPTUN; L-SURF Recommendation www.uptun.net; www.l- surf.org 39 PIARC Fire and Smoke Control in Road Tunnels 05.05.B PIARC Recommendation PIARC (1999) 40 PIARC Road Tunnels: Operational Strategies for Emergency Ventilation PIARC Recommendation PIARC (2008) 41 PIARC Road Safety in PIARC Recommendation PIARC (1995) TABLE 25 (continued) (continued on next page)

83 • The regulations and guidance need to provide better con- sideration of the inter-activity of all systems that interact in a tunnel. Integrated approaches shall be applied to tun- nel fire safety. • Better identification with regard to human behavior of both tunnel users and operators is important, as well as identification of the means to improve safety. • Consideration shall be given for technical innovations that allow more ambitious safety objectives. TUNNEL VENTILATION AND INTERNATIONAL STANDARDS REQUIREMENTS Ventilation for fire and smoke control requirements in the international standards are summarized based on the literature review conducted for this effort. When there is a fire, the fol- lowing safety criteria have to be applied in the design: 1. The purpose of controlling the spread of smoke is to keep people in a smoke-free environment as long as possible. This can mean one or both of the following: • That either the smoke stratification must be kept intact, leaving more or less clean and breathable air under- neath the smoke layer (applicable to bi-directional or congested unidirectional tunnels) or • That smoke must be completely pushed to one side of the fire (preferably applied to noncongested unidi- rectional tunnels where there are normally no people downstream of the fire). 2. People must be able to reach a safe place in a reasonably short time and cover a reasonably short distance. Emer- gency exits are provided whenever necessary. 3. The ventilation system must prevent smoke from spread- ing to uninvolved areas. 4. The ventilation system must be able to produce good conditions for fire fighting. 5. In the event of a fuel fire, secondary explosions result- ing from incomplete combustion have to be avoided. Therefore, the ventilation system must be able to deliver enough air for the complete combustion or dilution of explosive gases. A suitable drainage system is provided to minimize the surface area where fuel evaporation takes place. There are two categories of ventilation used in most tunnels: natural and mechanical. Appendix F1 (web-only) Tunnels 05.04.B 42 PIARC Integrated Approach to Road Tunnel Safety R07 PIARC Recommendation PIARC (2007) C3.3 43 NVF Ventilation av Vägtunnelar (Ventilation of Road Tunnels) NVF Sub Committee 61: Tunnels Nordic Road Technical Association Report of a Nordic working group NVF 1993 44 ASTRA Tunnel Task Force, Final Report Swiss Federal Roads Office Recommenda- tions for improved safety May 2000 45 PWRI/Japan Road Tunnel Technology in Japan PWRI no. 3023 Public Works Research Institute Technical Memorandum Ministry of Construction, 1991 46 PWRI/Japan State of the Road Tunnel Equipment Technology in Japan—Ventilation, Lighting, Safety Equipment Public Works PWRI Vol. 61 Public Works Research Institute Technical Note Ministry of Construction, 1993 47 PWRI/Japan Report on Survey and Research on Tunnel Ventilation Design Principles (Tunnel Ventilation Design Principles—Draft) Public Works Research Institute Survey Report Technology Centre of Metropolitan Expressway (1993) 48 European Thermal Network Fire in Tunnels FIT Technical Report Thermal Network FIT supported by European Community G1RT-CT- 2001-05017 From numerous sources. UN = United Nations; EU = Europan Union; PIARC = World Road Association (l’Association mondiale de la route). TABLE 25 (continued)

provides comparison tables on tunnel ventilation require- ments in different national (including NFPA 502, 2008 edi- tion) and international standards. It covers requirements for natural ventilation, transverse ventilation, and emergency exits pressurization. Natural ventilation relies on natural phenomena and traf- fic piston effect to renew the air in the tunnel. This ventila- tion system can be very effective for the dilution of pollutants (especially for one-way tunnels); however, it is not possible to rely on natural ventilation for safety purposes. Indeed, in the event of a fire in a tunnel, traffic will most likely stop, and the ventilation is only provided by natural phenomena that could be only partially deterministic (as the chimney effect). However, the main component of the ventilation will be quite uncertain (as meteorological components) and there- fore unreliable. Naturally, ventilated tunnels rely primarily on atmospheric conditions to maintain airflow and provide a satisfactory envi- ronment. The main factor affecting the environment is the pres- sure differential created by variations in elevation, the ambient air temperature, or wind effects at the boundaries of the facility. Unfortunately, most of these factors are highly variable with time and, therefore, the resultant natural ventilation is neither reliable nor consistent. Because of the number of different parameters that interfere in the choice to ventilate a tunnel or not (length, location, traf- fic, type of vehicles using the tunnel, and so forth), it is not pos- sible at this moment to express universal recommendations about the limits of the natural ventilation, especially the allow- able length without mechanical ventilation. A tunnel that is long or experiences frequent adverse atmos- pheric conditions requires fan-based mechanical ventilation. Among the alternatives available for road tunnels are longitu- dinal and transverse ventilation. Longitudinal ventilation introduces or removes air from the tunnel at a limited number of points, primarily creating longitudinal airflow along its length, from one portal to the other. Longitudinal ventilation can be accomplished either by injection, using central fans, using jet fans mounted within the tunnel, or a combination of injection and extraction at inter- mediate points. In longitudinal ventilation systems, using jet fans or por- tal nozzles (often called a Saccardo system), a longitudinal airflow sweeps all exhaust gases from the entrance to the exit portal. The only feasible way to evacuate smoke with longitudinal ventilation is by pushing it through the tunnel toward the por- tal. However, the airflow velocity necessary for such operation is the cause of turbulence and affects the smoke stratification 84 downstream of the fire. This phenomenon is more evident at higher air velocities. The smoke stratification can also be dis- turbed by the longitudinal slope of the tunnel (especially when air flows downwards) and by vehicles. Smoke from a fire in a tunnel with no slope will naturally tend to propagate in both directions owing to buoyancy effects. If the ventilation is in operation, the smoke will tend to be driven in the direction of the ventilation airflow. At low tun- nel airflow speeds, the buoyancy-induced flow is not entirely overcome and some smoke will flow upstream, which is often termed “backlayering.” The backlayering distance may be defined as the distance from the fire where the upstream smoke velocity is eliminated by the tunnel ventilation flow. Hence, a backlayering distance of zero would imply that no smoke flows upstream. The tun- nel air velocity required to achieve this condition is termed the “critical velocity.” Air velocity to prevent backlayering depends on the FHRR Q, the tunnel area A, and height H. Air velocity increases with the FHRR, but then levels off as the HRR increases. The design of the ventilation system and its operation must take into consideration that, owing to the presence of the lon- gitudinal airflow, the zone downstream of the fire is exposed to smoke and hot combustion gases. This can lead to suffoca- tion or burns for users in this zone. Any possible design mea- sure aiming for a safe escape from the dangerous section (fire area or downstream) must be taken. For this reason, the pres- ent UPTUN recommendations take into consideration the fol- lowing cases. A tunnel with one-way traffic not designed for queues (a nonurban area) has a ventilation design that can assume that drivers downstream of the fire are free to escape by means of their own cars, whereas drivers upstream will not. Tunnels located in nonurban areas are generally not situated in fre- quent congestion situations. Therefore, the relevant ventila- tion systems are generally not designed for queues. Nonurban tunnels, which are frequently congested, have instead to be designed for queues. The event of a fire ignited by vehicles involved in a secondary accident in the presence of other vehi- cles trapped downstream is possible, but the relevant proba- bility is low. This case is almost never taken into account in the design phase. If necessary, the risk of such an occurrence can be reduced by automatic incident detection and a traffic control system. The required longitudinal air velocities preventing smoke backlayering must be calculated by considering the following parameters. Meteorological parameters, especially longitudi- nal, can influence the performance of the ventilation systems. The ventilation system must have sufficient capacity to pro- duce the required air velocity against a stated adverse wind

85 pressure. The difference in pressure can be evaluated using the following simplified equation of Bernoulli: where: Δρ represents the pressure induced by wind, ρ the air density, ω the wind speed, and k a design parameter that depends on the configuration of the portals. This effect was studied by Blendermann (54) (see Figures 23 and 24 and Table 26): The orientation of both tunnel portals with respect to the prevailing winds is a very significant parameter. The effec- tive wind resistance (or thrust) is a function of the angle between the direction of the wind and the direction of the air flow entering or exiting the tunnel. • The traffic condition must also be evaluated. When eval- uating the necessary thrust in case of a fire, it must be assumed that a certain number of vehicles can be trapped in the tunnel and their presence reduces the performance of the ventilation system. The number of vehicles trapped can be assessed according to the design mix of traffic (percentage of passenger cars and heavy vehicles), the level, and the performance of the current road operation and traffic control system available for the tunnel. • For the effects of fire on the air flow, several aspects must be taken into account: – In the event of a big fire, the high temperature induces an increase of air volume (resulting from expansion) and therefore of air speed, as a result of which the air friction losses increase. – The density decreases, friction velocity increases, and the overall local losses increase. Δρ ρω= 1 2 262k ( ) – The blockage effect of the fire on the longitudinal airflow produces a supplementary local head loss. – With a tunnel with a steep grade, the chimney effect can be raised to significant values. – The decrease of air density results in the lowering of the driving force of the jet fans that work in the hot air. The reversibility of the system can be helpful during the fire fighting phase. When planning the reversing of the air, it must be taken into consideration that such operations can take a longer time, depending on the ventilation system, the tunnel geometry, the fans used, and other conditions. The reversal of jet fans is generally not recommended during the evacuation phase, even if the fire is located near the entrance portal. In the period between the ignition of the fire and the reversal of the jet fans, the smoke already can have traveled several hundred meters. When the smoke layer flow is reversed, it will be spread over the whole cross section, whereas during the people evacuation phases it is important to maintain good visibility conditions. Therefore, only after everyone is out of the tunnel can the reversal of the air flow direction take place. The reversing can be eval- uated in the event of a traffic jam inside the tunnel, but it must be a human choice, not an automatic configuration. Table 27 summarizes the recommended ventilation opera- tion in case of fire. In the case of twin tunnels, reversing the flow in the non- incident tunnel can prevent the circulation of smoke evacu- ated through the portal of the twin tunnel. Such circulation of smoke can also be prevented by civil engineering work (the distance between the twin portals, protection walls between portals, and so forth). The ventilation system needs to be designed to meet the previous requirements in case of a fire. For the design and FIGURE 23 Mean Wind Pressure Coefficients (54).

choice of all equipment it has to be taken into account that the hot smoke, traveling over the whole tunnel length, can seri- ously affect the installations (especially if the tunnel has a thermal insulation). Cables, junction boxes, and all other nonprotected parts of the ventilation system have the same fire resistance as fans. Special requirements shall be provided to jet fans operat- ing in fire emergency: • The strength of a normal aluminum blade falls quickly at high temperatures, although it depends on the type of alloy. When high air temperatures cannot be avoided, it is important that steel blades be chosen. • Owing to high temperatures, the length of the blades grows more quickly than the housing enlarges. The blade tips then tend to block the rotation. Abrasive tips may be introduced or a larger distance between blades and housing provided. 86 • A normal fan motor has to be cooled by outside air to meet the cooling requirements. However, there are motors available that have a very high resistance with- out external cooling. • All the auxiliary equipment as well as the wiring of the fan has to meet the air temperatures. For these reasons, fans must be designed and built to with- stand high temperatures. There are several national standards for the heat resistance of fans, ranging from 250°C (482°F) for 1 h (Austria, the Netherlands, United Kingdom, and the United States), 250°C (482°F) for 1.5 h (France), 300°C (572°F) for 1 h (Norway and Sweden), and 400°C (752°F) for 1.5 h (France and Switzerland). Where fans are distributed along the tunnel, a limited fan redundancy is suggested and can avoid the use of fireproof fans. In case of a fire, the temperature decreases rapidly when (a) (d) (b) (e) (c) (f) (g) FIGURE 24 Some configurations of tunnel portals tested by Blendermann (54).

87 the distance from the fire sight increases. It may be cost- effective to envisage the destruction of a few jet fans. For a tunnel with one-way traffic, designed for queues (an urban area), the ventilation design must take into considera- tion that cars can likely stand to both sides of the fire because of the traffic. In urban areas it is usual to find stop-and-go traffic situations. Therefore, this case generally applies to urban tunnels of sufficient length. For a tunnel with two-way traffic, where the vehicles run in both directions, it must be taken into consideration that in the event of a fire vehicles will generally be trapped on both sides of the fire. Transverse ventilation uses both a supply duct system and an exhaust duct system to uniformly distribute supply air and collect vitiated air throughout the length of the tunnel. The supply and exhaust ducts are served by a series of fixed fans usually housed in a ventilation building or structure. A vari- ant of this type of ventilation is semi-transverse ventilation, where either a supply or exhaust duct is used, but not both. The balance of airflow is made up within the tunnel portals. The purpose of controlling the spread of smoke is to keep people as long as possible in a smoke-free environment. This means that the smoke stratification must be kept intact, leav- ing a more or less clear and breathable air underneath the smoke layer. The stratified smoke is taken out of the tunnel through exhaust openings located in the ceiling or at the top of the sidewalls. It is important to indicate that all supply air ducts and all extraction smoke ducts be very tight. Continuous extraction into a return air duct is needed to remove a stratified smoke layer out of the tunnel without dis- turbing the stratification. However, the following conditions must be fulfilled: • The longitudinal velocity of the tunnel air must be below 2 m/s (394 fpm) in the vicinity of the fire incidence zone. These were the observations in the Japanese full-scale tests. With higher velocities, the vertical turbulence in the shear layer between smoke and fresh air quickly cools the upper layer and the smoke then mixes over the entire cross section. • With practically zero longitudinal air velocity, the smoke layer expands to both sides of the fire. The smoke spreads in a stratified way for up to 10 min, even without smoke extraction (depending on the tunnel and fire conditions). After this initial phase, smoke begins to mix over the entire cross section, unless by this time the extraction is in full operation. With an air velocity of around 2 m/s (394 fpm), most of the smoke of a medium-size fire spreads to one side of the fire (limited backlayering) and starts mixing over the whole cross section at a distance of 400 to 600 m (1,312 to 1,968 ft) downstream of the fire site. This mixing over the cross sec- tion can also be prevented if the smoke extraction is activated early enough. Additional Feature Portal Above Ground Level Portal Below Ground Level With vertical side walls With sloping bounds — Figure 24 (a) Figure 24 (d) * Dividing Wall Figure 24 (b) Figure 24 (e) * Light Adaptation Section )f(42erugiF)c(42erugiF )g(42erugiF**maD Source: Blenderman (54). Longitudinal Ventilation Evacuation Phases Fire-fighting Phase One Tube with Two-way Traffic (not recommended in the U.S. and many other countries) The smoke stratification must not be disturbed: - longitudinal air velocity is quite small - no jet fans working in smoke zone Avoid backlayering of smoke: - higher longitudinal velocity - direction of airflow adaptable Two Tubes with One-way Traffic Normal free traffic: Avoid backlayering of smoke: sufficient longitudinal air velocity in the same direction as traffic flow. Congested traffic, or fire at the end of the queue behind an accident, or one tube used bi-directionally: Same as one tube with bi-directional traffic for the two phases. TABLE 26 CONFIGURATION OF TUNNEL PORTALS TESTED BY BLENDERMANN TABLE 27 LONGITUDINAL VENTILATION OPERATION IN TUNNELS WITH ONE-WAY AND TWO-WAY TRAFFIC

• Vehicles standing in the longitudinal air flow increase strongly the vertical turbulence and encourage the ver- tical mixing of the smoke. • In a transverse ventilation system, the fresh air jets entering the tunnel at the floor level induce a rotation of the longitudinal airflow, which tends to bring the smoke layer down to the road. This is the reason for the sugges- tion to throttle the fresh air rate from one-half to one-third of full capacity, depending on the initial fresh air jet momentum. No fresh air is to be injected from the ceiling in a zone with smoke because this increases the amount of smoke and tends to suppress the stratification. • In reversible semi-transverse ventilation with the duct at the ceiling, the fresh air is added through ceiling openings in normal ventilation operation. If a fire occurs, as long as fresh air is supplied through ceiling openings, the smoke quantity increases by this amount and strong jets tend to bring the smoke down to the road surface. The conver- sion of the duct from supply to extraction must be done as quickly as possible. Continuous or Concentrated Smoke Extraction (Single Point) The traditional way to extract smoke is to use small ceiling openings distributed at short intervals throughout the tunnel. Another efficient way to remove smoke quickly out of the traf- fic space is to install large openings with remotely controlled dampers. They are normally in an open position where equal extraction is taking place over the whole tunnel length. In case of a fire, the single-point extraction is achieved in the fire location by remote control of the dampers. Recent tests by CETU and the Memorial Tunnel fire tests have proven the advantages of this system. To facilitate maintenance, there are systems in use where the large dampers are held by a mag- net in a closed position. In the fire zone, the magnets release the damper mechanism automatically by command from fire detectors and the dampers then open by gravity force. How- ever, this system does not allow the openings to close if a smoke plume moves to another place in the tunnel. Extraction Capacity Once a design fire and its amount of smoke production have been chosen, a permissible length over which the smoke may spread has to be fixed. Depending on the type of exhaust openings (fixed or remote-controlled), the extraction capacity per unit tunnel length in the fire zone is derived. In general, an extraction system needs less total exhaust volume when remote single-point extraction dampers are installed than with fixed openings. However, it also needs to be considered that in the first phase of the fire between the start of the smoke spreading and full operation of the exhaust system with large dampers, the smoke may have spread 1 km or more from the fire site depending on fire detection and ventilation system 88 operation design. Therefore, it is not sufficient to only open a few exhaust openings near the fire, but a minimum exhaust rate along the whole ventilation section is suggested as well. An extraction strategy needs to be developed depending on the type of tunnel and its ventilation system. The extraction capacity over the tunnel length that is per- missible for smoke to spread must exceed the smoke rate gen- erated by the fire, because the openings will not only exhaust smoke but inevitably some fresh air as well. Single-point Exhaust Opening The spreading of smoke over the entire length of the tunnel can be prevented by a large extraction of tunnel air directly above the traffic with suitable extraction ports. This system works best in conjunction with jet fans (see Figure 25) or por- tal (Saccardo) nozzles to localize smoke around openings and to prevent smoke from being driven by natural factors (such as wind and tunnel grade) and spreading along the tunnel. It is usually part of longitudinal ventilation with one or several central exhaust shafts. The exhaust capacity and the longitudinal velocity cre- ated by the jet fans in the tunnel section filled with smoke have to be matched and controlled under operation; it does not matter whether the smoke is stratified or spread over the entire tunnel cross section. The recommended extraction value is based on a cross-sectional area times longitudinal velocity. The system must be able to extract a longitudinal airflow of 3 to 4 m/s (591 to 787 fpm) and the small air veloc- ity in the following ventilation section toward the exhaust opening to prevent the spreading of smoke beyond the suc- tion point. Fresh Air Supply for Transverse Ventilation During fires, it is suggested that the fresh air jets enter the tunnel near the road surface. Their exit velocity and the dis- tances between the individual jets are small in order to obtain a uniform fresh air layer above the road. A large tunnel fire creates strong longitudinal airflows to supply the oxygen to the fire. With a continuous transverse fresh air supply along the tunnel this longitudinal velocity is reduced, which minimizes the air mixing with the smoke layer. Fresh air jets entering from ceiling openings are unfavor- able. When they enter the tunnel vertically, they destroy the smoke layer, induce smoke into the jet, and thus suppress smoke into the fresh air layer. The exit velocity of these ceil- ing supply air jets is to be small. Fresh air jets entering from the ceiling are stopped imme- diately after the fire alarm sounds in the ventilation section.

89 For longer tunnels, it is suggested that the fresh air outlets be positioned near the road surface. Fans in the exhaust air duct are exposed to a mixture of very hot air from the immediate area surrounding the fire plus cooler air farther from the fire. This mixture of hot and cooler air then travels in the duct and gets more cooled down. Tests in the Zwenberg Tunnel in Austria or in the Memo- rial Tunnel in the United States gave air temperatures at the fan below 250°C (482°F), even when the fire was very near the fan station. Memorial Tunnel test results are presented in Table 21 in chapter nine. A fire resistance of the fans to 250°C (482°F) could be considered sufficient for most of the fire events, but needs to be checked by design. When fans are located close to or in the exhaust air open- ings of the single-point extraction system, the exhaust fan temperatures must be evaluated in the design. Control of Longitudinal Velocity for the Single-point Extraction System To maintain smoke stratification, a low-speed longitudinal air velocity is required to push smoke to one side of the fire, which can be achieved by jet fans or Saccardo (portal) noz- zles. However, the process of activating the required number of jet fans within a few minutes after fire ignition is compli- cated owing to the turbulent nature of tunnel airflow, large cross-section area, and changing winds and other natural fac- tors. This requires air velocity measurements as average over cross section (1): • Required accuracy ± 0.3 m/s, • Short response time and time resolution, and • Proper positioning of sensors. Also, it is important that no jet fan is turned on in or near a place where there is smoke, as this would immediately destroy the smoke stratification. The usual way to control the longitudinal velocity is to provide several independent ventilation sections. When a tunnel has several ventilation sections, a certain longitudinal velocity in the fire section can be maintained by a suitable operation of the individual air ducts. By reversing the fan operation in the exhaust air duct, this duct can be used to sup- ply air and vice versa. Whatever the means of controlling the longitudinal air velocity are, their operation has to be preprogrammed accord- ing to the location of the fire in the tunnel to ensure the opening of the required dampers and activation of required fans. Tunnel ventilation fans that are to be used in a fire emer- gency shall be capable of achieving full rotational speed from a standstill within 60 s. Reversible fans shall be capa- ble of completing full rotational reversal within 90 s (NFPA 502). The emergency ventilation system shall be capable of reaching full operational mode within a maximum of 180 s of activation. Fans could be activated sequentially based on fire zones. Emergency Exits Pressurization NFPA 502 calls for a tenable environment provided in the means of egress during the evacuation phase. Emergency “exits” shall be pressurized in accordance with NFPA 92A. Appendix F1 (web-only) provides a comparison analysis of the pressurization requirements of emergency exits in the national and international standards. FIGURE 25 Tunnel with a single-point extraction system (55).

TUNNEL FIRE PROTECTION, FIRE FIGHTING, AND INTERNATIONAL STANDARDS REQUIREMENTS Tunnel fire protection standards requirements are summa- rized based on the literature review conducted for this report. A tunnel fire is more effectively fought in its early stages. Some vehicles using the tunnel may carry fire fighting equip- ment; however, if such equipment is unavailable or insuffi- cient then fire fighting equipment installed in the tunnel can be used. There could be cases when the installed equipment is insufficient to manage the fire size. Therefore, equipment such as fire hydrants and fire hose valves are used by the fire department. Generally, hand-held extinguishers are provided in the tunnels; however, the required distances between them vary. Pressurized fire hydrants or fire hose valves are provided for most tunnels. Appendix F2 (web-only) provides comparison tables on tunnel fire protection requirements in different national (including NFPA 502, 2008 edition) and international stan- dards. It covers the fire fighting equipment (extinguisher, hose reels, and so forth) and water requirements. Typically, design fire size and physical tunnel configuration drive water flow and pressure requirements. No European standards have requirements for installation of a fixed fire suppression system. Such requirements do exist in Japan and Australia: • In Australia, AFAC (the Australian Fire Authorities Council) strongly advocates the installation of suit- ably designed, manually controlled deluge/sprinkler systems. • In Japan, sprinkler systems are required for the following tunnels: Class AA, Class A tunnels more than 3000 m long and with average daily traffic of greater than 4,000 vehicles/day, and bi-directional tunnels. Sprinkler sys- tems have been installed in more than 80 tunnels in Japan. In Sweden, fixed fire suppression systems would be in- stalled if it leads to a significantly raised level of safety for people according to risk analysis. In Korea, the Gwangju Institute of Science and Technol- ogy (GIST) recommends installation of a fixed fire suppres- sion system for tunnels that are more than 3000 m long with traffic flow of more than 60,000 vehicles × kilometers/ day/tube for bi-directional tunnels or more than 90,000 vehi- cles × kilometers/day/tube for uni-directional tunnels. A sprinkler system has been installed in the Joogryeng Tunnel in Korea (56). 90 More discussions on fixed fire suppression systems is pro- vided in chapter twelve of this report. TUNNEL FIRE DETECTION, NOTIFICATION, AND INTERNATIONAL STANDARDS REQUIREMENTS Fire-detection systems are necessary to alert tunnel operators of potentially unsafe conditions. The fire-detection principles are based on the parameters determined by the fire: • Smoke • Heat • Flames (radiation). There are a range of methods available to detect fire and smoke within road tunnels, including linear (line-type) heat detection, closed circuit television (CCTV) video image smoke detection, flame detection, smoke and heat detectors, and spot-type heat and smoke detection. Selections of fire- detection systems are made depending on the fire safety goals and objectives and the overall fire safety program. This includes notifying occupants to allow for safe evacuation, modifying tunnel operations, initiating a fire life safety sys- tems operation, and notifying emergency responders. The key objective is prompt notification while preventing nui- sance alarms. Some jurisdictions require that “listed devices” be used. This is a design challenge because there are few listed devices for tunnel application. Depending on the nature of the fire, either smoke, flame, or heat can start developing first. Consequently, multi-sensor alarm systems are better suited for automatic control. The National Fire Alarm Code (NFPA 72 of 2010), PIARC (PIARC Technical Committee C3.3 2007, PIARC Technical Committee C3.3 2007, PIARC Technical Com- mittee C3.3 2008) and several research projects provide addi- tional information to assist with the development of detection system concepts and designs. The Fire Protection Research Foundation (FPRF) of the United States and the National Research Council (NRC) of Canada sponsored a two-year international research project to investigate available fire- detection technology suitable for tunnel application. The main objective idea of the study was to provide information for use in the development of performance criteria, guide- lines, and specifications for tunnel fire-detection systems, and to be used for updating NFPA 502. The NRC has conducted fire tests in a laboratory facility and performed CFD analyses to investigate the impact of various tunnel fire scenarios on the performance of fire- detection systems. They have also conducted full-scale fire tests in an operating road tunnel in Montreal in collaboration with the Ministry of Transportation of Quebec and in the Lincoln Tunnel in New York with the support of the Port Authority of New York and New Jersey. One of the objec- tives was to investigate the false alarm potential in a tunnel

91 environment (57). A discussion of these methods along with some of the advantages and disadvantages for each system follows. Linear (Line-type) Heat Detection There are several types of line-type heat detectors in use today. The three main types are Analog (Integrating) Linear Heat Detectors, Digital Linear Heat Detectors, and Fiber Optic Linear Heat Detectors. • Analog (Integrating Heat Detector) systems incorpo- rate a multilayer cable. A core conductor is covered by a temperature-sensitive semiconductor with an outer conductor. The inner and outer wires are connected to a control panel that monitors the resistance of the semiconductor. A temperature rise in the cable causes a reduction in the conductor’s resistance and detection occurs when the monitored resistance reaches a pre- determined setting. • Digital Linear Heat Detectors consist of two polymer- insulated conductors. The insulation melts at a set temperature. Detection in this system occurs when the insulation melts, which allows the conductors to make contact with each other. In some systems, the control panel connected to the sensing element is able to deter- mine the distance where the conductors made contact and determine the location of the fire. • Fiber Optic Linear Heat Detectors consist of a control panel and quartz optical fibers. The control unit houses a laser that sends a beam through the fiber optic cable. These systems provide detection using the Raman Effect, which senses temperature changes by evaluating the amount of light scattered. One of the main advantages of this type of detection is that the cable is suitable for harsh environments. In addition, because these products are essentially a two-conductor cable, there is flexibility in the installation: patterns can be used to meet spacing requirements and the cable can be routed around obstructions. Many of these products can determine the approximate location of the fire based on either a reduc- tion in the conductor’s resistance or light scattered for fiber optic systems. Some manufacturers of these systems also promote the longevity of their systems; with a useful system life of approximately 30 years. Disadvantages of linear heat detectors are that some require cable replacement after a fire. With tunnels typically being extremely large, with long open spaces, providing detection using linear heat detection can require a large amount of cabling. If the objective is to detect a fire from a moving vehicle, such as a tractor-trailer, the design will need to assess whether the cable will be heated sufficiently to actu- ate. There are known bus tunnel events where there was a new linear heat detection system that was unable to detect fire. Considerations shall be given to a large ventilated tunnel volume, which makes fire detection difficult. CCTV Video Image Smoke Detection Video detection is a relatively new smoke detection technol- ogy that uses real-time video images. Through proprietary software, this technology is able to detect fires by analyzing changes such as brightness, contrast, edge content, loss of detail, and motion. Video smoke and heat detection has a number of advan- tages. First, the system cameras can be used for other sys- tems such as traffic control monitors and security, as well as smoke and fire detection. Second, detection is based on real- time video images; therefore, each camera can cover a large area. Third, this technology is capable of detecting fires in moving vehicles. Fourth, emergency responders can be pro- vided with real-time video information about a fire. The visu- als can provide useful information such as fire size, source, and location, which can help operators and responders to efficiently react to the incident. Interest in the use of the automatic video image detec- tion (VID) system for road tunnel protection has increased because of its quick response to the fire or security incident, real-time video images for use in monitoring events, and its ability to guide evacuation, rescue, and firefighting. Many tunnels are already equipped with VID systems for traffic man- agement and security protection. Recent studies conducted by the FPRF at NFPA also showed that the VID fire-detection sys- tem was one of most promising detection technologies for the use in road tunnel protection. A new generation of video detection technology is being developed. It includes volume sensors; meaning that it looks for fire and smoke within the entire observation space of the Internet protocol (IP) address of the camera. This fundamen- tal advantage results in faster, reliable fire and smoke detec- tion and, most importantly, provides a visual picture of the situation to the on-duty operator. Some cameras are both Underwriters Laboratory (UL) listed and Factory Mutual (FM) approved, and have flame and smoke detection devices that are also FM approved. The cameras have passed tunnel tests in Canada, New York, and China (58). Use of camera- based detection systems may fulfill a multi-purpose regimen if the camera image can be used for security, traffic, and/or road conditions as well. To prevent nuisance alarms, multiple detections and con- firmations are required before notification or system activa- tions can occur. This also provides redundancy in case one detector fails. When the alarm conditions are met the event file is created and sent to the remote monitoring station oper- ating the system. The on-duty operator receives the notifica- tion of the alarm with live video from the location. Designers

will need to review listings and approvals with the authorities to determine the suitability of these devices for specific pro- jects. Because these systems rely on video imaging, some of them may have a difficult time in detecting shielded fires. This can be a disadvantage for other systems as well. Flame Detectors Flame detectors are fixed devices that are capable of sensing fire by the amount of radiant energy that is emitted. Detectors in this category include ultraviolet, infrared, combination ultraviolet/infrared, or multiple wavelengths infrared. Flame detection systems have a number of advantages. These systems typically work well in and are suited for harsh environments such as those found in tunnels. Some of the more challenging fires in road tunnels involve combustible and flammable liquid. Flame detectors are well-suited for detecting these types of fires. These devices are also capable of detecting fire signatures that include a range of varying wavelengths, which provide design flexibility when devel- oping the system. A disadvantage of these systems is that historically they have been prone to nuisance alarms caused by interference from arc welding, electrical arcs, lightning, metal grinding, artificial lighting, and in some cases even sunlight. Newer designs account for these interferences. As with many of other systems, detection can be delayed for shielded fires. Spot Detection A number of traditional smoke and heat detection systems can be used to detect fires in road tunnels. These systems include the use of projected beam-type smoke detectors, duct smoke detectors, and heat detectors. • Duct smoke detectors are provided in the tunnel ventila- tion ducts. Typically, the actual detector is mounted on the outside wall of the duct. The detector is connected to a metallic tube that extends across the duct. The tube has calibrated holes that draw air into the tube, which is then directed to the detector. • There are many different types of heat detectors. Typi- cally, detection is either by an abnormally high tem- perature; a pre-determined temperature rise. Some heat detectors are capable of detecting both temperature and rate of temperature rise. One of the main advantages for these systems is that they are readily available and there is a wide pool of contractors capa- ble of installing these systems; therefore, there is no need to hire a specialized contractor. Compared with the other sys- tems, these systems are relatively inexpensive. 92 Projected beam smoke detectors typically consist of a detec- tor unit with a receiver. A beam of light is sent from the detec- tor to the reflector and if the beam is obstructed it will trigger an alarm. A disadvantage of projected beam and duct-mounted detectors is that they are prone to nuisance alarms from diesel exhaust, which is almost always present in road tunnels. Appendix F3 (web-only) provides comparison tables on tunnel fire smoke detection requirements in different national (including NFPA 502, 2008 edition) and interna- tional standards. In a few national guidelines for road tunnels, there are val- ues for the maximum detection time and degree of accuracy of fire location, including fire loads and airflow speed. Fire- detection time is a critical element in a tunnel fire event. Detection time depends on fire development and ventilation conditions and varies from 1 to 2.5 min. Maximum design detection time is directly related to fire development. Table 28 provides requirements for fire-detection and fire alarm systems in road tunnels in various countries. The fol- lowing can be concluded from this table: • An alarm triggers no later than 60 s after ignition or at fire energy load not exceeding 5 MW. • The fire alarm system shall respond to relatively low energy release rates of 1.5–5 MW (5–17 MBtu/hr), meaning that it must be capable of detecting fire at an early stage. • Detection shall be made possible without restrictions to airflow speed in the tunnel up to 6 m/s (1,181 fpm). • The accuracy of spotting the fire shall be between 20 and 50 m (65.6 and 164 ft). Notification Once the detection system is implemented, it can be used to provide automatic notification to any or all of the following: motorists, tunnel controllers, external agencies (traffic), emer- gency responders, etc. A combination of fixed signage (speed, lane control, rescue zones) and variable message signs (VMS) provide a workable mix of visual instructions. The ability to use VMS as part of the preprogrammed emergency response scenario could prove helpful by stopping or slowing traffic; instructing motorists to turn off their vehicles, leave their keys, and exit; and direct them to clear a traffic lane and move to the optimum exit path. Manual controls are always used for VMS. This allows incident command to communicate with emergency respon- ders, motorists, and others if radio communication fails. In addition to visible notifications, AM/FM radio override is common, but less effective given the reduced use of com-

93 mercial radio. Motorists can also be notified by a public address system once they are stopped and/or are out of their vehicles. Caution is placed when automatic notification is used for the motorists. Tunnel fires may change quickly and can be dif- ficult to predict. Using fire-detection systems to decide which direction to exit the motorists and to initiate suppression and ventilation is not foolproof. Directing the escaping motorists in the wrong direction could dramatically increase their risks. However, using automatic detection to close the entrance por- tal and to warn motorists who are approaching an incident in the tunnel is an accepted practice in some jurisdictions. Conversely, using traffic controls to encourage motorists to continue to drive out of the tunnel may be important for tunnels that use longitudinal ventilation. In this case, traffic controls downstream of the portal may be essential to clear the tunnel past the incident and to provide room for motorists so that they can drive out to safety before being overwhelmed by smoke and heat that has been pushed along the tunnel by longitudinal ventilation. These notifications are a key ingredient for the incident command by providing location, type of incident, conditions, and size of the incident. In turn, motorists can be instructed on what to do while emergency responders are enroute and tunnel staff initiate their emergency procedures (60). Recently, intelligent evacuation notification technolo- gies have been developed. One of the vendors uses elec- troluminescent lighting technology—an uninterrupted illu- minated path to the exits with a continuous light source located near the walkway floor (E-Lume-A-Path) (61). Another vendor uses a multi-directional low-level light- emitting diode guidance system (62). The advantage of those technologies is that they can be preprogrammed to guide tun- nel users in the correct direction depending on ventilation system response. This is especially important when compli- cated tunnel ventilation schemes are used to eliminate the wrong direction for evacuation. TUNNEL EGRESS AND INTERNATIONAL STANDARDS REQUIREMENTS Design provisions allow for safe evacuation during a fire when heat, smoke, and other products of combustion are released into the tunnel. Road tunnels are long, narrow, and underground, often with limited opportunities for stair cores to grade. An emergency ventilation and fire suppression approach needs to be fully coordinated with the evacuation plan and the emergency response plan to provide a comprehensive overall life safety program for the tunnel. Egress systems must provide for safe evacuation under a wide range of emer- gency conditions. The emergency response plan must help facilitate evacuation and allow for appropriate responses to emergencies. NFPA 502 does not allow for emergency exits or exit doors leading to exits to be spaced more than 300 m (1,000 ft) apart, with spacing justified by engineering analysis (63). For uni-directional traffic with a longitudinal ventilation sys- tem, this spacing will largely depend on the fire-detection system and its ability to detect fire as soon as possible such that ventilation can be activated to take smoke under control. They differ between self-rescue and assisted rescue from road tunnels. The majority of tunnel occupants are to rescue themselves during a fire event. Standards Detection Time Fire Load Detection Distance Germany RABT 2003 <60 s at V air up to 6 m/s (1,181 fpm) 5 MW (17 MBtu/hr) <50 m (164 ft) CH 2001 Draft Directive on Road Tunnels )tf6.56(m02<weiverrednUs06< A RVS 9.282; 4.7.2002 9.261 V air up to 3 m/s (591 fpm) • Pre-alarm <60 s • Alarm <90 s; V air over 3 m/s (591 fpm) • Pre-alarm <120 s • Alarm <150 s 1.5 MW (5 MBtu/hr) and 3.5 MW (12 Btu/hr) <10 m (32.8 ft) NFPA 502 Addresses delay expected between ignition occurring and an alarm being initiated <15 m (49.2 ft) (section 7.4.1.4) Source: Fire Protection in Vehicles and Tunnels for Public Support (59). TABLE 28 REQUIREMENTS FOR FIRE DETECTION AND FIRE ALARM SYSTEMS IN ROAD TUNNELS IN VARIOUS COUNTRIES

The following safety provisions have been applied in road tunnels worldwide (emergency passenger exit for users): • Parallel escape tubes (egress corridor) • Emergency cross passages to a parallel tunnel • Shelter • Direct pedestrian emergency exit (shafts, portals). Appendix F4 (web-only) provides comparison tables on tunnel egress requirements in different national (including NFPA 502, 2008 edition) and international standards. It cov- ers parallel escape tubes (Table F4-1), emergency cross pas- sages (Table F4-2), shelters (Table F4-3), and direct pedestrian emergency exits (Table F4-4). The comparison shows that cross passage vehicle accesses are required by the international standards, if possible, with a distance of approximately 1 km (3,280 ft). Turning areas shall be provided for long tunnels. TUNNEL INCIDENT RESPONSE AND INTERNATIONAL STANDARDS REQUIREMENTS The strategies adopted by the emergency services will recog- nize that an accident could rapidly escalate into a major inci- dent and that a fast response is necessary. Tunnel rescue strategies in an emergency organization are planned, tested, and implemented. The tunnel operator coordinates the rescue strategy. A communication strategy is essential in tunnels. Another important issue may be how to enter a particular tunnel in a safe way. Access times for the emergency services can be analyzed from different perspectives, including the location of the accident, turnout from the rescue station, turnout from another place or, if relevant, with reserve rescue forces when the normal forces are occupied. The conditions within the tunnel and the exposure limits are identified and reviewed regularly so that proper precau- tions can be taken by rescue staff in a fire situation. An emergency response plan is implemented for prede- fined events. This specifies the initial responses and so forth as defined in NFPA 502. Specific rescue effort plans are to be made based on the emergency response plans. Also insti- tuted is a common information/media plan, which is agreed on between the emergency services and the tunnel operator. This will include providing information activities to media with the aim of keeping tunnel users and the media focused on safety aspects. The plan defines the information responsibilities during and after an accident; specifically, what information the tunnel operator can communicate. Also implemented is an education plan for all rescue staff, reflecting both the educa- tion of newly employed staff and refresher courses. Likewise, an emergency service exercise plan is devel- oped. These exercises can help to train new staff in com- 94 munication or in the use of technical systems, such as fire hydrants. A common exercise plan between the emergency services and the tunnel operator staff is especially important. The need for specific tunnel rescue facilities or equipment is analyzed and incorporated into the emergency services normal rescue facilities if it is found favorable from an effi- cient and safe rescue point of view. In event of an accident, an efficient and clear alarm for resources is essential. When emergency services from differ- ent organizations are involved, special attention needs to be paid to the advantages of a computer-based alarm system, ensuring that all involved parties receive the same information. The emergency services and the tunnel operator regularly perform common functional tests to demonstrate the technical functionality as well as the staff’s ability to handle the equip- ment, such as the communication radios. It is essential that reliable, efficient, and fast communication be established for the rescue staff internally in the tunnel and externally with the rescue centers. The rescue forces must be able to communicate at least with their own control center during the incident to obtain the information about the cause of the event. They also need to be able to communicate between the inside of the tun- nel and their control center. Coordinated interventions are always to be performed according to the rescue plans, at least with regard to the num- ber of resources for the initial rescue phase. The intervention follows plans concerning how and in which way to enter the tunnel. It also shows how to organize the rescue vehicle dis- position, both inside the tunnel and for resources waiting out- side the tunnel. Special consideration shall be given to means and methods to remove victims. The following means for emergency access for rescue staff has been used in road tunnels worldwide: • Separate emergency vehicular access gallery • Cross-passage vehicular access • Emergency lane • Direct pedestrian access (lateral, upstairs, shaft) • Turning areas • Emergency services station at portals. Appendix F5 (web-only) provides comparison tables on tunnel incident response requirements in different national and international standards. It covers a separate emergency vehicle gallery access (Table F5-1), cross-passage rescue vehicular access (Table F5-2), emergency lane (Table F5-3), direct pedestrian emergency access (lateral upstairs shaft) (Table F5-4), turning areas (Table F5-5), and emergency ser- vices station at portals (Table F5-6). The size of a fire in a road tunnel will have a considerable effect on the ability of the Fire and Rescue Service to perform

95 effective rescue and/or firefighting operations. When tack- ling fires in road tunnels, personnel and equipment need to be capable of dealing with fires of any magnitude. Handling fires from private cars within twin-bore tunnels will almost always be within the capabilities of a firefighting force. However, the same fire in a single-bore tunnel could lead to considerable difficulties, depending on whether there is any airflow through the tunnel or whether there is a venti- lation system capable of evacuating smoke from the fire or fixed fire suppression system available. The factors that will set the capacity requirements for fighting a fire in a tunnel will be: • The number of people that the rescue and fire services must assist to safety. • The size of the fire and thus the temperature and thermal radiation power that will face the firefighters. • The distance that the firefighters have to travel in a smoke-filled environment to reach the fire. Fires in trucks, and especially gasoline tanker fires, are likely to reach output levels that it can be difficult to effec- tively contain. The emergency response time is to be based on NFPA 1710. Figure 26 provides a tunnel fire fighting timeline. How much water will be needed to put out the fire? This is an important question to answer, as it determines the number of jets used over a certain period of time. In turn, these jets require a certain number of firefighters, working under difficult conditions. The quantity of water needed to extinguish a vehicle fire in a tunnel, based on the extin- guishing requirements for fires occurring in nonresidential buildings, is given in Table 29. In such instances, the fire- fighters had direct access to the fire. In this context, we need to remember that vehicle fires are particularly difficult to put out, which means that the following simplifications must be seen as an absolute minimum requirement in terms of water quantities. The firefighters need to get close to a vehicle on fire to fight the fire because of the low ceiling of the tunnel. The water flow rate then has to be maintained for a significant period to put out the fire. It may take about 30 min, with at least the 1,250 l/min quantity of extinguishing water, to put out a fire in a truck. It would be possible to deal with fire gases using ventilation to increase the airflow; however, thermal radiation from the fire and from any residual back- FIGURE 26 Fire fighting timeline (14, 59). Type of Vehicle Fire Area (m2) Heat Release (MW) Minimum Extinguishing Water Requirement (l/min) Number of 360 l/min Jets Private Car 10 5 226 1 Van 35 15 462 2 Truck 200 100 1,250 4 Sources: Rhodes and MacDonald (20) and Ingason et al. (64). TABLE 29 ABSOLUTE MINIMUM WATER REQUIREMENTS FOR EXTINGUISHING A VEHICLE FIRE

layering will be difficult to contend with. Development of some form of protection against thermal radiation is needed to assist tackling fires of this type, perhaps through the use of water mist jets or water curtain jets. Portable radiant bar- riers and vehicles already in the tunnel are used for protec- tion from thermal radiation. SUMMARY Although each national and international standard provides specific information related to design fire, most of the speci- fied information addresses the same general performance concerns. This summary highlights some safety features that have limited or no recognition in NFPA 502, or a difference in approaches between NFPA and most of the other interna- tional standards noted. • For ventilation design in the event of a fuel fire, sec- ondary explosions resulting from incomplete combustion need to be avoided. Therefore, the ventilation system must be able to deliver enough air for the complete com- bustion or dilution of explosive gases. • PIARC documents and other international standards allow longitudinal ventilation in single-tube nonurban tunnels with 2-way traffic based on risk analysis relying on smoke stratification, although this is not recom- mended in the United States. • No European standards have requirements for installa- tion of a fixed fire suppression system. Such require- ments exist in Japan and Australia: – In Australia, AFAC (the Australian Fire Authorities Council) strongly advocates the installation of suit- ably designed, manually controlled, deluge/sprinkler systems. – In Japan, sprinkler systems are required for Class AA tunnels, Class A tunnels more than 3000 m long and average daily traffic of more than 4,000 vehicles/day, and for bi-directional tunnels. Sprinkler systems have been installed in more than 80 tunnels in Japan. – In Sweden, fixed fire suppression systems would be installed if leading to a significantly raised level of safety for people according to risk analysis. • Automatic fire detection with no allowance for man- ual fire detection is required by many international standards. – In a few national guidelines for road tunnels there are values for the maximum detection time and degree of accuracy of fire location, including fire loads and air- flow speed. Fire-detection time is a critical element in a tunnel fire event. Detection time depends on fire development and ventilation conditions and varies from 1 to 2.5 min. Maximum design detection time is directly related to fire development. 96 – A new generation of video detection technology is being developed. It includes volume sensors, which search for fire and smoke within the entire observation space of the IP address of the camera. This fundamen- tal advantage results in faster, more reliable fire and smoke detection and, most importantly, provides a visual picture of the situation to the on-duty operator. Some cameras are both UL listed and FM approved and have flame and smoke detection devices that are also FM approved. The cameras have passed tunnel tests in Canada, New York, and China. Use of camera- based detection systems may fulfill many purposes if the camera image can be used for security, traffic, and/or road conditions. Some international standards provide requirements in the tunnels for: • Shelters • Lay-bys • Parallel escape tubes • Separate emergency vehicular access gallery • Cross-passage vehicular access • Emergency lanes • Direct pedestrian access (lateral, upstairs, shaft) • Turning areas • Emergency services station at portals. Such requirements are not found in NFPA 502 and need additional studies of the experience from international standards. Recently, intelligent evacuation notification technol- ogies were developed using electroluminescent lighting technology—an uninterrupted illuminated path to the exits with a continuous light source located near the walkway floor or multi-directional low-level LED guidance system. The advantage of those technologies is that they can be pre- programmed to direct tunnel users in the right direction depend- ing on ventilation system response. This is especially important when complicated tunnel ventilation schemes are used to eliminate the wrong direction for evacuation. The following common gaps in the national and interna- tional standards and regulations were reported: • The regulations and guidance need to provide better con- sideration of the interactivity of all systems that interact in a tunnel. Integrated approaches shall be applied to tunnel fire safety. • Better identification with regard to human behavior of both tunnel users and operators, as well as identification of the means to improve safety. • Consideration shall be given for technical innovations that allow more ambitious safety objectives.

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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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