Evacuation in Complex Environments - Industrial Fire Journal

Fourth International Symposium on Tunnel Safety and Security, Frankfurt am Main, Germany, March 17-19, 2010 

Evacuation in Complex Environments - An Analysis of 

Evacuation Conditions at a Tunnel Construction Site 

Håkan Frantzich & Daniel Nilsson 

Department of Fire Safety Engineering and Systems Safety, Lund University, Sweden 

ABSTRACT 

Experiments have shown that the evacuation characteristics in complex environments differ 

significantly from evacuation in public buildings. This has to do with, for example, the necessity to 

move along paths that may not be optimal for evacuation, i.e., movement on ladders and through 

narrow passages. In some cases, protective clothing has to be removed before evacuation can be 

initiated, which means that the pre-movement time can be quite long. Another difference compared to 

public building evacuations is that the attitudes among the workers towards fire safety education and 

safety drills is sometimes very negative. Results from an evacuation experiment from an environment 

identified as complex are presented; evacuation from a tunnel boring machine (TBM) where refuge 

chambers were used. In addition, some preliminary modelling results are presented for the tunnel in 

question. The paper will focus on evacuation in complex environments and, more specifically, it will 

attempt to 

- identify movement characteristics for people in complex environments, 

- discuss technical measures that can improve evacuation, and 

- suggest management procedures that can improve evacuation 

KEYWORDS: tunnel, evacuation, construction site, fire 

INTRODUCTION 

By tradition most evacuation analyses have focused on the problems associated with evacuation of 

large populations in public environments. This is partly due to the need for building codes to 

rationally regulate evacuation capacity of doorways, corridors and stairways etc. Another reason for 

investigating the evacuation capacity for large populations is the need to find input data for egress 

modelling for large crowds. This has also lead to the development of several egress models, which are 

suited for handling large populations. The typical premises for these models are public buildings, e.g., 

sports arenas, mass transit systems and high rise buildings. Much attention has also been focused on 

places where people may not be able to evacuate by themselves, e.g., total institutions [1], or 

buildings where people may not be familiar with the layout and evacuation routes, e.g., retail stores 

[2, 3]. Evacuation in these types of environments is therefore rather well documented. 

However, knowledge about evacuation in industrial premises and at construction sites is relatively 

limited. Evacuation conditions for people that work in industrial premises or at construction sites 

could be very different from the conditions that can be expected in public buildings. Experiences from 

fires in such occupancies reveal major difficulties during fires and evacuation e.g. the fire in Store 

Baelt rail tunnel construction in 1994 [4]. Most importantly, the environments are sometimes very 

complex, i.e., difficult to evacuate due to both cognitive and physical obstacles. For example, a 

construction site is constantly changing, which means that the evacuation routes can be modified from 

one day to another and may not always be clearly marked. This type of constant modification can 

make way-finding problematic. At many construction sites and industrial premises people also have to 

181


evacuate through narrow passages or down ladders, which means that there is an apparent risk of 

injury. The environmental conditions may also impose other difficulties such as problems hearing an 

evacuation alarm because of background noise and problem moving to a place of safety due to narrow 

passages and obstacles in the path of travel. These types of factors make the environment complex 

with regards to fire evacuation which can form extra hazards that have to be dealt with during 

operation in the complex spaces. 

Much of the preventive work safety relies on traditional procedures and not much work has been 

published focusing on the special problems facing workers during evacuation from these complex 

environments. Special attention has therefore been made to investigate the special conditions that may 

be present for these environments. 

The nature of the problems in the complex environments are similar to those in traditional assembly 

type buildings, i.e. there are problems getting aware of the fire threat, the cues related to fires have to 

be interpreted and a decision making process has to be initiated and finally there is a movement 

distance between the location of the people and a safe place. Obviously, there are differences which 

are related to the increased complexity of the environment. Some aspects that may increase the 

complexity are: 

- Visual access – limited visual overview, dim lighting, darkness, etc 

- Sound level – noisy environments, background noise, etc 

- Familiarity – unfamiliar environment, constantly changing environment, etc 

- Obstacles and narrow passages – manholes, drops, etc 

- Difficult passages or bottle-necks – ladders, remote locations (e.g. cranes), airlocks, etc 

- Work that needs to be terminated properly due to safety reasons – welding, crane operation, 

etc 

- Isolated environment – long distance to a safe location, low visual access to the surroundings 

etc. 

In order to demonstrate some of the factors influencing the evacuation conditions present in the 

complex environments an evacuation experiment was performed in a tunnel boring machine (TBM) 

used for constructing a railway tunnel in Sweden. The TBM, which is over 240 m long and has a 

diameter of over 10 metres, has currently proceeded approximately 5 kilometres into the mountain. 

The typical problems for this scenario are that there is only one escape route, the noise level is high 

and it is difficult to have visual access of the environment. 

The safety for the tunnel workers has also been investigated using a simple one-dimensional 

evacuation model. The model determines the possibility for continuous evacuation for persons in a 

tunnel given a prescribed fire development. It is necessary for the tunnel construction operator to 

investigate different fire scenarios that can occur as performing experiments and drills can only 

capture some aspects of the possible outcome of an accident. Therefore modelling and physical 

experiments have to complement each other to broader the picture and provide input for additional 

safety assessment. The paper, therefore, introduces a simple MATLAB model that can be used for an 

initial sensitivity analysis of the evacuation situation for the tunnel workers. 

The evacuation research is part of the ongoing research project “Fire safety in tunnels during 

construction” which is supported by The Swedish Civil Contingencies Agency (MSB) and led by the 

Technical Research Institute of Sweden in Borås. The purpose for the main research project is to 

investigate the fire behaviour, the occupant evacuation conditions and the needs for a proper rescue 

operation in tunnels, which are under construction. The research project is running to the end of 2010. 

This paper is based on a paper [5] presented at the 4 th International Symposium on Human Behaviour 

in Fire, 13-15 July 2009. 

182


GENERAL CONDITIONS FOR THE EVACUATION EXPERIMENT 

The Tunnel Boring Machine (TBM), figure 1, is used at the Hallandsås rail tunnel site in southern 

Sweden. Two parallel tunnels will be constructed for increasing the rail capacity between several 

large cities in western Sweden. According to the latest information from Banverket, the Swedish Rail 

Administration, the tunnel will be open for traffic in 2015. Currently the TBM is located in the 

mountain in the first of the two tubes and at this stage the tunnelling consortium wanted to test the 

evacuation and rescue procedures during fires. An exercise was planned and executed to investigate 

the evacuation capacity, the responses by the workers in the tunnel and in the TBM. In addition 

investigations of movement patterns and walking speeds were also measured and other special 

conditions relevant for the construction site. 

Figure 1. Schematic figure of the TBM, side view. Total length approximately 240 m, drill head 

diameter 10,6 m. 

In case of an emergency the procedure for the tunnel workers is to move to a safe location inside the 

TBM, a refuge chamber in which the workers can stay during a fire. The TBM has two refuge 

chambers, one fixed to the TBM and another that can drive away from the TBM along the tracks on 

the bottom of the constructed part of the tunnel, figure 2. The tracks are usually used for moving 

personnel and goods between the TBM and the outside. As the procedure for the workers is to stay in 

the refuge chambers it was considered important to investigate the attitudes among the workers to see 

how they perceived their situation in case of a fire. Another issue of interest was how communication 

between the workers was maintained during the emergency as people with different nationalities are 

among those present in the TBM. It was also assumed that movement paths should be documented in 

order to better prepare for safer walking paths inside the TBM. 

Figure 2. Illustration of the mobile refuge chamber (to the left) and the permanently fixed refuge 

chamber inside the TBM. 

183


The TBM is a more than 240 m long moving construction site with mainly two floors or decks. It is 

constructed of several so called trailers linked together in the tunnel. On the lower deck the 

maintenance train can enter to deliver goods and tunnel elements used to line the tunnel as it proceeds. 

The upper deck is mainly used for the machinery of the TBM, the personnel mess room and pilot 

cabin from which the TBM is operated. In the front end the huge excavation wheel (drill head) is 

located cutting the hole in the mountain. The TBM is equipped with an automatic fire alarm which 

can be readily heard all over the TBM. The alarm uses an alternating tone signal. Detectors are 

located at extra hazardous places but not all over the machine. At places for storage of flammable 

liquids and hydraulic equipment fire extinguishing systems are located. There are also sprinkler 

curtains in the TBM separating the machine into three sections. Evacuation is supposed to be 

performed along one of the TBM sides on both decks. The decks are linked by stairs at several 

locations and it is rather easy to move between the decks. The escape routes are marked with 

traditional signs and equipped with emergency lighting. During normal operation approximately 20- 

25 persons operate the TBM and the highest allowed number in the tunnel is 40 persons set by the 

contractor. 

Participants 

The participants in the experiment were the normal crew on the TBM but they were working with 

maintenance tasks. This means that the number of participants in the TBM was about 24 and none of 

them were aware of the experiment, which mean that the evacuation was unannounced. The exact 

number of participants is not known but estimated by the number entering the refuge chambers (23 

persons entered the refuge chambers) during the evacuation. The last participant, i.e. the TBM pilot, 

remained at his working location as a safety precaution. He was told to stay in place by one of the 

observers at the start of the experiment. From the demographic part of the questionnaire it was found 

that all participants except one were men. The mean age was 39 years (between 27 and 56) and they 

came from different countries namely Sweden, Denmark, UK, France, Australia and Poland. All of 

them, except one, could communicate in English. All of them had previous experiences from fire 

drills and fire extinguishing training. Two of the participants had previous experience from real tunnel 

fires and one of those experienced the fire in Store Baelt tunnel in Denmark in 1994 [4]. 

In addition approximately five other persons were in the TBM as observers and safety officers in case 

the experiment had to be terminated. 

Procedure 

The experiment was performed during a period of normal maintenance on the TBM on 7 November 

2008. Before the experiment was started more than 25 video cameras were mounted at different 

locations in the TBM. The locations were chosen to have a good chance of observing initial actions by 

the workers and also for observing chosen walking paths and measuring walking speeds. The purpose 

was to measure walking speeds both on a horizontal surface and in stairs. In addition a number of 

cameras were located inside the two refuge chambers in order to be able to observe the behaviour of 

the participants when they have entered the chambers. 

The scenario for the experiment was that a fire had started in a maintenance train approximately 1 km 

behind the TBM. This means that there was no fire onboard the TBM and no smoke were present 

during the experiment. But as the fire blocks the only escape route to the outside such a scenario is 

considered serious and an evacuation of the TBM shall always be performed in case of a fire in the 

tunnel. However, the actual threat to the workers on the TBM is not present but the uncertainty of the 

situation can cause an at least as important concern among the workers. 

The alarm to the TBM came from the outside to the pilot informing him about the fire in the tunnel. 

He initiated the fire alarm in the TBM after some ambiguity about procedures. According to the 

normal procedure he shall then leave for the refuge chambers but due to safety reasons he stayed in 

the pilot cabin after instructions by one of the observers. 

184


At the time when the alarm was initiated the workers were at different locations inside the TBM. Six 

persons were in the mess room, one at the drill head and two were working on the lower deck with 

some maintenance work. The locations of the other persons are not known in detail as they were 

outside the coverage areas of the video cameras. After the fire alarm was initiated the evacuation to 

the refuge chambers started and the workers left their present locations. 

When the workers had been inside the refuge chambers for approximately 15 minutes one of the 

observers entered the chambers and handed out questionnaires which were returned after completion. 

In total 20 questionnaires was returned and demographic questions were also included in the 

questionnaire. After approximately 40 minutes after the alarm was initiated the experiment was 

terminated and the workers returned to their previous tasks. 

Results 

Pre-movement time 

The responses by the participants were very swift. Those who were able to observe from the video 

cameras responded within less than 30 seconds. At the drilling head one person who was engaged 

with some work left his place only after four seconds after the alarm started. He was alone at the 

location. 

The persons sitting in the mess room also responded very quickly, i.e. only after 10 seconds after the 

alarm started. One person in the mess room was delayed for 30 seconds 

Fire alarm 

From the questionnaires it is evident that all the workers perceived the fire alarm. Most of them 

responded because they heard the fire alarm and understood that they should evacuate and move 

towards the refuge chambers. All of them responded with answers that associated the fire alarm signal 

to fire, evacuation, danger and other similar. 

Exit choice 

One of the factors to investigate was how the persons chose exit routes to the refuge chambers. In 

general all of the workers used the walking paths normally used to access the different parts of the 

TBM. This means that they used the paths along the right side of the TBM (seen from behind the 

TBM). As it is normally easier to walk on the lower deck many of the persons chose to climb down at 

the nearest stair of reach the lower deck. The refuge chambers are also located at the lower deck so 

this choice is probably also affected by this knowledge. 

Attitude 

One key element in determining exit behaviour from areas of complex environment is the attitude 

towards fire safety issues and evacuation exercises among the workers. The outcome of an evacuation 

is sometimes dependent on a rapid and correct response by the persons exposed to the fire threat. 

Therefore the questionnaire contained a number of questions related to find information on how the 

workers thought about fire safety and similar. As the answers were assumed to differ between persons 

being together with colleagues, i.e. those who initially were in the mess room or in the pilot cabin and 

those who were alone or being with just one other colleague, i.e. being at other locations in the TBM, 

those two groups were separated. The responses are presented in figure 3 giving the average values of 

the responses to each question in the questionnaire for the two groups and for all together. The 

numbers indicate the degree to which the person disagrees to the statement. The scale range from 1 

which is “strongly agree” to 4 which corresponds to “strongly disagree”. 

185


State to what extent you agree with the following statements. 1="Strongly 

agree" amd 4="Strongly disagree" 

0 1 2 3 4 5 

a) 

b) 

all 

c) 

d) 

e) 

f) 

remote from TMB control 

cabin and mess room 

in TBM control cabin or 

mess room 

g) 

h) 

i) 

j) 

k) 

l) 

m) 

n) 

o) 

p) 

Figure 3. Questionnaire results from TBM evacuation. The statements are presented in table 1 below. 

186


Table 1. Questionnaire statements for the experiment in Hallandsås tunnel. 

Statements 

a) I thought there was a fire when I heard the alarm. 

b) Evacuation drills are unnecessary. 

c) I thought it was a drill when I heard the alarm. 

d) Evacuation drills take unnecessary much time to perform. 

e) I thought an accident had occurred when I heard the alarm. 

f) I thought something wrong with the TBM when I heard the alarm. 

g) Fire drills take unnecessary much time to perform. 

h) Tidiness is necessary for fire safety. 

i) I thought the tunnel had caved in when I heard the alarm. 

j) I thought there was some electrical failure when I heard the alarm. 

k) Signs (se below) indicating the routes to the refuge chamber are not necessary. 

l) I thought something was wrong with the alarm when I heard the alarm. 

m) I thought it was a false alarm when I heard the alarm. 

n) Evacuation drills are necessary. 

o) I thought something serious had happened when I heard the alarm. 

p) Evacuation drills are a good way to practice. 

It is clear from the answers that persons being alone or together with just one colleague were more 

uncertain about the situation than those who were sitting in for example the mess room. Persons being 

at other locations than the mess room and pilot cabin did to a higher degree associate the alarm signal 

to fire and emergency, cf. statements a) and c). People sitting together in the mess room could agree 

more rapidly that this is probably an exercise and not a real fire. 

Other statements resulted in more similar answers, i.e. were not depending on the location of the 

participants and who they were together with. Notably is that all of the participants agree that tidiness 

is important and that safety procedures are important in order to keep a high level of fire safety. 

Walking speed 

The walking speed for the participant was rather fast at the point where speed was measured. In the 

stair the speed varied between 0,75 m/s and 1,0 m/s measured along the slope. The walking speed 

along a horizontal surface was naturally higher and ranged between 1,0 m/s and 1,7 m/s. The data 

points for the lower value included also some vertical movement as the participants jumped from a 

walking path along the TBM to the lower deck, a distance of approximately 0,8 m. This means that 

the average speed between two measuring points was lower than the actual local walking speed but 

the difference at the point of measuring cannot be determined. The walking speed at another 

measuring point showed higher values, up to 1,7 m/s. The variation was low as most of the 

participants moved together in groups with almost the same speed. 

Evacuation time and general observations 

In total the evacuation took approximately 3 minutes to perform from the time when the fire alarm 

started to all participants were inside one of the refuge chambers. The first participants arrived to the 

refuge chambers approximately 1 minute from the start of the fire alarm. The first ones to arrive 

started to prepare the mobile refuge chamber for the case they had to abandon the TBM and drive out 

of the tunnel. After this they entered the mobile refuge chamber. 

187


A comment from the participants during discussions after the experiment revealed that 

communication between the participants on the TBM and between the participants on the TBM and 

persons outside the tunnel did not work properly. Communications over the radio during the 

experiment was sometimes in Swedish, which made it difficult for participants not understanding 

Swedish to follow the conversation. The formal procedure is that all communication shall be in 

English. 

The participants also mentioned that there was a lack of information regarding the situation from 

persons outside the tunnel. As there was no clear sign of a fire at the TBM the situation was rather 

ambiguous for the participants when they were sitting in the refuge chambers. One person also 

mentioned that he was anxious that someone had not noticed the fire alarm and still be at a place in 

the TBM. The information about the exact number of persons on the TBM during the experiment was 

uncertain to the persons supposed to be the only ones at the machine. 

EVACUATION MODELLING 

The evacuation model used for investigating the possibility for tunnel workers to safely evacuate a 

tunnel compares the time for evacuation with the time for untenable conditions to occur. The model is 

based on a one-dimensional approach of smoke spread in the tunnel. This means that the smoke 

temperature, gas concentrations, visibility etc only depend of the distance from the fire and the time. 

The vertical variation is ignored and it is assumed that homogenous conditions apply, which is true at 

a distance from the fire. Close to the fire the model will provide a not so good prediction of the 

conditions. 

The smoke spread and subsequently the spread of toxic gases, temperature etc are calculated using the 

model provided by Ingason [6] and only need to have a HRR curve as an input. It is assumed that the 

fire is located in the most remote part of the tunnel construction site, i.e. where the actual tunnel is 

excavated. 

The evacuation model is based on the assumption that a person continues to move away from a fire, 

after an initial pre-movement time, at a speed that depends on the smoke conditions, i.e. the visibility. 

Reduction in visibility reduces the walking speed. The person can initially already be at a distance 

away from the fire. The movement continues as long as the person is conscious and that depends on 

the accumulated toxic dose of the smoke gases, mainly carbon monoxide, carbon dioxide, low oxygen 

concentration and elevated temperature. The toxic accumulation is derived using the Fractional 

Effective Dose theory proposed by Purser [7]. It is assumed that unconsciousness occur when the 

person has accumulated a toxic dose equivalent to FED = 1,0. 

A preliminary analysis was made on the Hallandsås rail tunnel using a 30 MW fire as the first 

assumption. The fire peaks at 30 MW at approximately 13 minutes from the fire start. The ventilation 

air supply to the construction site is assumed to result in a supply air velocity of 0,5 m/s across the 

tunnel section. 

Some of the results from this initial analysis are presented in table 2 which show whether or not 

evacuation is possible and how far from the fire a safe refuge must be located. 

Table 2. Basic results from the sample analysis. 

Scenario Pre-movement 

time, sec 

Initial distance between 

person and fire, m 

Distance when FED 

= 1,0 occurs, m 

Time when FED = 

1,0 occurs, minutes 

1 60 0 - never 

2 120 0 250 22 

3 120 50 - never 

4 120 30 - never 

5 150 30 300 25 

188


From analysing the different scenarios it is evident that as long as the evacuation can be initiated with 

only a small delay most of the occupants in the tunnel can evacuate safely. But if they respond slowly 

or are close to the fire so they already are within a smoky section they will have difficulties to escape. 

One shall, though, be aware of that in this case the fire is rather large and only a small part of the 

analysis is presented. But the purpose with these results is to demonstrate that it is quite easy to 

perform an evacuation analysis of the tunnel construction site in order to get an idea of the fire threat. 

Additional analyses, for example regarding heat radiation on the workers, have to be performed to get 

a broader picture of the workers’ safety. 

DISCUSSION 

Evacuating from a complex environment can be difficult to perform without any additional 

improvements of the environment or additional information or education of the persons subjected to 

the environment. The experiment shows that the outcome of an evacuation can depend on the attitudes 

among the persons in the environment even if that factor is not part of the environment but rather as 

an external factor associated to how the environment is used. 

However, given the conditions the overall impression is that the evacuation was prompt and efficient. 

The response time was very short for most of the participants indicating that they were trained to 

handle the situation. The attitudes regarding safety in the case of a fire among the participants given 

from the questionnaires showed that they were aware of the seriousness if the situation was for real. 

Working in building sites, industries etc may need to use different equipment, cranes or machinery 

that cannot be shut down immediately at the time the fire alarm starts. Because of safety reasons some 

equipment need a shutting down period before it is safe to leave the work place. There is no simple 

solution for handling these problems but care has to be taken to prepare for emergency closure 

procedures of such equipment. Mainly this is a management procedure and the first priority in the 

case where the fire alarm starts must be to shut down the equipment instead of questioning the reason 

for the alarm. This problem was not tested in a fully realistic manner as the TBM was shut down for 

maintenance and only running in stand by mode. Some traditional maintenance work provided some 

insights into the problem. 

A quick response will most likely require a clear and understandable signal that can be readily heard 

from all relevant locations. The fire alarm in the TBM was possible to be heard from all locations in 

the machine which contributed to the fast response. This is most important for cases when visual 

access is limited which usually is the situation for these locations as it defines the complex 

environment. The use of fire alarm is therefore essential. The evacuation from the TBM clearly shows 

the need to use a fire alarm as this was the first sign of an unusual condition in the tunnel. 

Initially it was assumed that the walking speed should be lower than what can be expected in other 

occupancies. But this turned out to be wrong. In the TBM the participants walked at least as fast as 

shoppers in a warehouse even if the walking paths were not as smooth as in the warehouse. The 

reason for this could be that most of the persons, mostly men, working in this type of environment are 

rather strong and well fit for the job. It must be assumed that they are slightly better suited for moving 

in the narrow passages and along uneven surfaces. In most cases it can also be assumed that the 

persons are familiar to the environment at least after spending some time in, for this case, the TBM. 

However, in many other complex environments narrow passages may still be a problem even if the 

persons are familiar with the conditions. Climbing a ladder through a narrow hole in a floor is much 

more difficult that using a stair. Elimination of difficult passages should therefore be considered if 

possible. 

189


CONCLUSIONS 

The main conclusions of the present study are: 

- In complex environments it is necessary to use well designed fire alarms in order to reach all 

persons with proper information. If possible the fire alarm should be a spoken message. 

- Signage indicating escape routes must be clearly visible even if the light in the environment is 

poor or uses a special colour. 

- Persons working in complex environments must be subjected to repeatedly evacuation 

exercises so they become with the familiarity with the situation. A fire in a complex 

environment is usually regarded more hazardous than others due to the complexity. 

- The combination of exercises (experiments) and modelling is necessary for having a full 

understanding of the difficulties during a fire in a tunnel during construction. 

REFERENCES 

1. Moss Haber, G. “Human behaviour in fire in total institutions; A case study”. In D. Canter 

(Ed.), Fires and Human Behaviour (pp. 137-154). John Wiley & Sons Ltd, Chichester, 1980. 

2. Shields, T. J., & Boyce, K. E. “A study of evacuation from large retail stores”. Fire Safety 

Journal, 35(1), 25-49, 2000. 

3. Frantzich, H. “Occupant Behaviour and Response Time – Results from Evacuation 

Experiments”. Proceedings of the 2nd International Symposium on Human Behaviour in Fire, 

pp 159-165, 2001. 

4. Tait, J., C., Høj N., P. “Storebælt eastern railway tunnel: Dania tunnel boring machine fire - 

analysis and recovery”. Supplement to Civil Engineering 114, special issue 1, Storebælt 

Eastern Railway Tunnel, 1996. 

5. Frantzich, H. & Nilsson, D. “Evacuation In Complex Environments - An Analysis Of 

Evacuation Conditions In a Nuclear Power Plant and A Tunnel Construction Site”. 

Proceedings of the 4th Int. Symp. on Human Behaviour in Fire, Robinson College, 

Cambridge, UK, pp 207-218, 13-15 July 2009. 

6. Ingason, H. “Fire dynamics in tunnels”. In A. Beard and R. Carvel (Eds.) The handbook of 

tunnel fire safety (pp. 231-266). Thomas Telford Publ., London, 2005. 

7. Purser, D. “Assessment of Hazards to Occupants from Smoke, Toxic Gases and Heat”. In P.J. 

DiNenno et al. (Eds.) The SFPE Handbook of Fire Protection Engineering, 4th ed. National 

Fire Protection Association, Quincy, 2008. 

190

Evacuation in Complex Environments - Industrial Fire Journal

Create successful ePaper yourself

Delete template?

Save as template?