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100 not be allowed to travel through the tunnel (conditions at which the RWS curve was obtained). Simple heat transfer equations do not allow for the mak- ing of a direct correlation between the timetemperature curve and the timeheat release curve. It appears that the known fire growth rates follow the super fast (highest increasing rate measured) temperature rise in the timetemperature curves. However, the use of HRR curves for the design is often allowed. When using HRRs instead of timetemperature curves for FIGURE 29 Fire emergency timetable (6, 66). calculating structural stresses resulting from a fire, a super fast increase of the HRR is to be used as it was observed with the Runehamar tests in Norway in late 2003. This phase is fol- lowed by a maximum design HRR according to the type of EMERGENCY EGRESS TIMELINE vehicle investigated. The egress timeline depends heavily on human behavior. The HRR within this scenario will be determined by the Human behavior in a tunnel fire emergency can be a compli- type of load that is allowed to pass through the tunnel as cated. Unfortunately, in general, people tend to do the wrong well as by the ventilation and fire suppression conditions, if thing in the event of a tunnel fire, such as staying inside their applicable. cars instead of heading for the emergency exits. Following the decay of the fire, a linear or steeper decrease Intelligent Transportation Systems (ITS), warning motorists is used. The duration of the maximum HRR can be deter- of any impending danger and providing them with valuable mined by using the burning load and type of fire suppression. early directions, could be the extremely helpful. At the very least, the equipment must be able to function Significant research has attempted to address such issues as for the duration of the anticipated escape and rescue time. It to why people in vehicles in tunnels do not leave their cars and must be considered that equipment in the direct fire zone may escape, but instead end up dying? Why do some people leave not withstand the fire for an extended amount of time. their vehicles and then return to them when the fire grows? Educating people and notifying them of danger is a separate subject. For design purposes, there is a need to assume that Time-of-Tenability people will realize the danger, be notified to evacuate, make the correct decision on the direction for evacuation, and go to For fire life safety an integrated approach is to be taken. Time- the point of safety. However, this may not happen immediately of-tenability can be understood by analyzing the entire system and some reaction time will be needed in realizing the danger with all components working together. of the situation. To develop a time-of-tenability final curve the project It could be assumed that occupants of vehicles will have must develop: noticed the fire event within 30 to 60 s of ignition if the fire is rapidly developed. After that, there is some reaction time A fire HRR curve as a function of time. needed to make a decision. The project may consider that A design evacuation (egress) curve as a function of people will not move until they hear an alarm and get direc- time. tion from the operator to evacuate. In addition, it is necessary A design systems response curve as a function of time. to add times for detecting and alerting, reaction and leaving the vehicles, and walking to a safe place, to know if people This time line is illustrated in Figure 29. can escape the fire safely. The sum of detection and alerting times depends on the type of fire detection and how the infor- The development of a fire, or the fire heat release curve, mation is given to people in their vehicles. Therefore, this was discussed in the previous chapters and is a function of: can take 2 to 5 min in manned tunnels. Maximum FHRR, The sum of the reaction times and leaving the vehicle is Fire growth rate (quadratic curve for either super fast, also difficult to estimate. For example, it takes longer for pas- fast, medium, slow fire growth rate), and sengers to escape a bus than a car. Therefore, the sum of these Fire decay rate. times may vary between 30 s and 5 min.

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101 FIGURE 30 Walking speed in irritating and nonirritating smoke (9). It is especially important when considering evacuation their eyes open. The volunteers attempted to compensate for from a bus. A German study, Fire Protection in Vehicles and this lack of orientation by using the walls for guidance. Tunnels for Public Transport (59) cites 2 min as the maximum period of time acceptable for evacuating a bus. Other studies Results suggest that in nonirritant smoke with an OD of report that 3 min is the expected time to fully empty a loaded 0.43 m (1.4 ft) (extinction coefficient of 1.0) walking speeds transit bus. are reduced to 0.5 m/s (98.4 fpm). However, in irritant smoke at an OD of 0.22 m (0.72 ft) (extinction coefficient of 0.5), the Walking speeds can also vary. Depending on age and state walking speed is reduced to 0.4 m/s (78.7 fpm) (see Figure 30). of health, people can walk at a speed from 1 to 1.6 m/s (197 to 315 fpm). PIARC suggests that the walking speed in a smoky environment (with some level of visibility) is from 0.5 m/s A series of experiments exploring the relationship between (98.4 fpm) to 1.5 m/s (295.3 fpm) (21). Consideration needs visibility in smoke and evacuation movement were conducted to be made for people with mobility impairments. in a smoke-filled corridor 20 m (65.6 ft) long. The experi- mental population consisted of 17 females and 14 males, The speed of movement for those who are mobility impaired ranging from 20 to 51 years in age. Experiments were con- was tested in Leipzig on the station's platform (60) and is ducted using both nonirritant and irritant smoke. People were presented in Table 31. This table shows that a walking speed asked to travel from one end of the corridor to the other, iden- of 0.5 m/s (98.4 fpm) can be considered as a reasonably good tifying when they could see a fire exit sign. Both the irritancy estimate. and the density of the smoke affected the volunteer's walking speed. Figure 30 shows the gradual decline of the recorded Depending on the number of evacuees (occupant load), a walking speed through nonirritant smoke as the density of the bottleneck may form approaching the cross passages or egress smoke is increased, whereas in irritant smoke the gradient is stairs. It is not possible to take fire and smoke under control far steeper. This was explained as being caused by the erratic immediately. Therefore, for several minutes, fire and smoke movement of the volunteers owing to their inability to keep will be driven by natural factors. This is the most important TABLE 31 SPEED OF MOVEMENT AND EVACUATION TIMES OF MOBILITY-IMPAIRED PEOPLE Movement Time Distance Users Speed of Movement 110 m (360 ft) Wheelchair Users 0.7 m/s (138 fpm) 150 s People with Prams/Carriages 1.1 m/s (217 fpm) 95 s People with Walking Aids 0.6 m/s (118 fpm) 175 s People with Infants 0.55 m/s (108 fpm) 190 s Source: Fire Protection in Vehicles and Tunnels for Public Support (59).