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Fire detectlonand suppression systems in roadtunnels
Volume 1 -Summary Report
by G I Crabb (TRl Ltd),M J Bullock (ChHtern international Fira
ltd) and
R H Harse (Symonds Group ltd)
PRJIS/17A/01
3/340
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TRL Ltd
PROJECT REPORT PRlIS/17 A/01
FIRE DETECTION AND SUPPRESSION SYSTEMSIN
ROAD TUNNELS
by G I Crabb (TRL Ltd),M J Bullock(Chiitern international Fire
Ltd) andRH Harse(Symonds Group Lid)
Prepared for: Project Record: 3/340 Use Of Fire Sprinkler Type
Systems In Road TunnelsClient: Quality Services, Civil Engineering,
Highways
Agency(Mr T Aloysius)
Copyright TRL LtdOctober 2002.
Thls report preesred for me Highways Agency must not be referred
to in any publication without thepermlesion of !he Highways Agency.
The views expreseed are those of the authors and not
necessarilythoseof the Highways Agency.
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Thls report bas been produced by TRL Ltd, under/as part of a
Contract placed by the Highways Agency.
Any views expressed are not necessarily those of the Agency.
TRl is committed tooptimising energy efficiency, reducing waste
and promoting recycling and re-use. In
support of theseenvironmental goals, this report has been
printed on recycled paper, comprising 100%
post-consumer waste, manufactured using a TCF (totaUy chlorine
free) process.
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CONTENTS
Page
EXECUTIVE SUMMARY 1
ABSTRAeT
..............................................................................................................................5
1 Introduction 5
2 Defniition of fires 6
2.1 Frequency '" 62.2 Size; development and duration
.................................................................................7
2.3 Spread 8
3 Types of tunnels ~ 8
3.1 Geometry 83.2 Design seenarios 9
4 Opraonal management
..................................................................................................10
4.1 Detection of fires
................................................................;....................................11
4.2 Initial response to a fire ~ 11
4.3 ther actions '" 114.4 After an incident 124.5 Training,
emergency exercises, safety management and review procedures 12
4.6 Operation of fire suppression equipment 124.7 Incident
records '" 14
5 Objec~ves of fire suppression systems 14
6 Fire control systems
.........................................................................................................16
6.1 Detection '" 166.2
Suppression................................................................................................................16
6.3 Sprinkler systems 176.4Pipework
...................................................................................................................17
6.5 J:>rainage.; 18
6.6 Priorities for further
research....................................................................................19
6.7 Pull-scale tests 20
7 Computer modellieg
..........................................................................................................20
8 Risk management. ,
'".................................................................22
9 Costsand benefits 23
9.1 Benohmark costs '" 24
9.2 Whole life costs 24
10 Conclusions 2510.1 PrimaJ)'safety ~ ~ ~ ~~ 2510.2 Escape
facilities ~ 25
10.3 Tunneloperation 26
10.4 Priorities following the outbreak of a fire
.................................................................26
10.5 Probabilities, costs and benefits 2611 Recommendations
27
11.1 Case studies 2711.2 Cemmunication and evacuetion 2711.3
Deseetion and suppression 28
11.4 Full-scale tests 2811.5 Computer modelling 28
12 References 29
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13 Acknowledgements 29
VOLUME 2
APPENDIX A Report by Chiltern International Fire AI-A79
Hydraulic Design Pro-forma Annex A1- Annex A6
Sketch schematic of sprinkler system
...................................... Annex B
CFD modelling questionnaire ...............................
,.....Annex Cl - C45
Report by Symonds Group
.................................................... BI - B29
Risk management.
...........................................................................
1 -14
Figure 4.1
...................................................................................
A l-C7
Figure 4.2 Cl - Cl5
Digital Equipment Corporatien v . Hampshire CC D1 - D5
APPENDIXB
APPENDIXC
APPENDIXD
[Appendices A,B, C and D are provided on a CD fitred into
lilplastic waUetat the
back ofthis volume ofthe report.]
VOLUME 3
RECOMMENDATIONS FORFUTHERRESEARCH
CONTENTS
I INTRODUCTION
2 OPTION 1: ESTABLISHMENT OF FIRE TESTFACILITY INTHE UK
3 QPTION 2: PAN-EUROPEAN PROGRAMME OF RESEARCH
4 THEWAYFORWARD
Al BACKGROUND
A 1.1 Problems of defining research option
Al.2 Basis of'options
A2 OPTION 1:ESTABLISHMENT Of TEST FACILITY IN THE UK FOR
FIRE RESEARCH
A2.1 Genera! requirements
A2.2 Test sectionsand equipment
A2.3 Test equipment
A2.4 Numerical Modelling
A2.5Personnel
A2.6 Reporting
A2.7 Number ef trials
A2.8 Timetable
A2.9 eostsA3 OPTION2: PAN-EUROPEAN OF RESEARCH.
A3.I . Genera!
A3.2 Developing a research proposal
A3.3 Testfacilities
A3.4 Test programmeA3.5 .Timtabl
A3.6 Cost
[Volume 3 is provided in separate covers]
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EXECUTIVE SUMMARY
PRIISI17A101: FIRE DETECTION AND SUPPRESSION SYSTEMS
IN ROAD TUNNELS: PHASE 1
by0 1Crabh (TRLLtd), M JBulloek (Chiltern International Fire
Limited) and RH
Harse (SYltlonds Group Limited)
Project.Manager:
3/340 Use of fire sprinkler type systems in rood tunnels
Mr T .Alpysius, Quality Services, Civil Engineering,
Highways
Agency
MrcrCrabb, TRLLtd
Project Reference:
Project O(ficer:
SCOPE OF TUE PROJECT
The objective of this first phase of the project is to provide
theHighways Agency
with adviee and recommendations on the use off1Xedfire
suppression systems in. road
tunnels. This phase was to investigate the capabilities
ofcurrent fire detection and
suppressin systems, their costs and benefits,experience of their
use, andto. make
recommendations for further research in the remaining two phases
ofthe.proJect
SUMMARY OF REPORT
Method
Two sub...contractors assisted TRL in this investigation,
Symonds Oroup .Ltd. was
commisstoned to provide information on the
classificationandfrequencyof.fires in
road tunnels, together with aclassification of UK highway
tunnels based onparameters that affect the installatien and use of
firedetection andssppression
systems within them, Chiltern International Fire Ltd was
commissioned to provide
informationon the operational management andcomputermodeUingof
lires in road
tunnels ...This included a review of the capabilities of current
fire .detection. and
suppression systems that might be used in road tunnels. The
applicability of these
systems was ranked through Value Engineering assessments.
A wide-ranging lirerature review has been undertaken; of
particularinterest were the
results of fire tests in road tunnels. Case-history evidence was
sought from tunnel
operators, particularly these with experieaee ofthe useof'fixed
suppression systems,
A~s~ll1al1agen1entstudY\Vascompleted. Thisranked
variousfn-escenariosfor road
tunn~l~inorder.of
risk:.this.was..derl~d.as.the.produet..of.au.assessedconsequenceprlorityanda
probabilityofoccurrence.priority. However, becanse of the
pancityof
data for sueh extremely rare eveats, the findings
aretentative.
Results
!he available dataindicate that, inthe UK, there are 4 fires per
108 vehicle
kilomefres.For .the .'averageUK. tunnel', definedas850rn long.
and .carrying46,OOO
vehiclesper day,this equatesto a reported fire every 21
months.However, it should
be noted that most fires are extmguished without any serieus
risk to life or limbor tothe continued operatien of the tunnel. The
risk of a serious fire is tentatively estimated
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to be 0.2 per 108 vehicle kilometres; this was based onthe fact
that about 5% of fires
are due.te vehiclecollisions. Thankfully, catastrophes, such as
the Mont Blanc tunnel
fire, aremuch rarer.
Four classesof veniele fire loads are defined: car bus, lorry
and hazardousload ..The
last hasthe grestest potentiel fire loading: on average. the
rate of hatrelease for thisclass is 150MW, the duration of the fire
is an hour and the maximum temprature is
1200EC
Thee classesoftunnel geometry relvantto the generationand
snppression of'fireare
defmed,and the implications of likely fire scenarios discussed'
for each. For a variety
of reaso,s, bi-directional tunnels pose a biggerproblem than
uni-diretional ones,
The order of priority forreeponding to a fire in a road tunnel
was identified as;
earlydetection
ass~ssment (by trained personnel) aletting theemergency
services
cletand simple emergeaey'procedures
cOl1ttolof ventilation
effective traffic control
provision ofeffective means of escape, and
the use of fire suppression equipment
Available detectionand suppression techniques are described and
ranked: the two
mostprmising detectionsystems are;
1 linear heat dereetion by optical fihre,and
2 digital image analysis of'clesedcireuit relevision (CCTV)
images.
Similarly,the two mostpromising suppression systems for further
investigation were;
1 longitudinal jet fan ventilation with targeted manual' fire
suppression (for uni-
directional tunnels only), and
2 water spray with fuel vapourabsorbenr additive.
A ValueEngineering analysis .identified iTIJNFIR.E'as tbe most
.promising of the
compu.ona.kt1uiddynamics
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Nevertheless, there is no doubt that an effeetive fire
suppression system could have a
pivotal role in substantially reducing the severity of a fire in
a road tunnel. Such a
system would have to be integrated with traffic control and
oommunication systems,
for example, into the overall management operatien for a tunnel.
However, as it
stands, a eonsiderable amount of research involving full-scale
fire tests is required to
investigate the cost-effeetiveness of fire suppression systems
in road tunnels. Therequirements of a research programme are
discussed in Volume 3 of this project
report.
IMPLEMENTATION
The next phase of this study should cover:
A study of the road tunnels in the UK to determine the relative
eostfbenefit ratiosfor various improvements 10 fire safety.
An investigation, using a driving simulator, of the
effectiveness of methods forcommanieating with drivers, botb
approaching a tunnel and in a tunnel where
thereis a fire. This would cover signage, alarms, means of
closing a tunnel, aswell as in-tunnel communications.
A review of the means and cost-benefits for collaborating with
European partnersto complete a programme of tests on dereetion and
suppression systems.
The use of Computational Huid Dynamies (CFD) for simulating
tunnel fires andtheirsuppression, and the validared of such
calculations, as best can be, by the
results of past, and perhaps new, full-scalefire tests.
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FIRE DETECTION AND
SYSTEMS IN ROAD TUNNELS
SUPPRESSION
ABSTRACT
Recent .serieus fires in tunnels on mainland Enrope have
focussed attention on the
safety ofroad. tunnels in the UK .. These fires demonstrated,
quite graphically, the
importance of early deteetion; incident planning and control;
communicationbetween
tunnel operators, emergency services and vehicle occupants;
means of escape; and
early andaccurate intervention to prevent a fire fromgrowing to
theextent that
oonditions. in the tunnel become dangerous, if not
life-threatening, for its users and
emergency services.
This report provides the fmdingsofa study undertaken to assist
the.Highways Agency
plan further research into tunnel safety, particularly the
applieability of firesuppression systems suehas sprinklers. AlLtbe
important points Iisted above were
considered. The study included anexamination of ..case records,
the results from
earlierresearch into tunnel fires,the stock of roadtunnels-in
the UK, the frequency
and sevent)' of tunnel fires, and tbe tecbniqaes available for
detecting and suppressing
fires and theconsequences of their use.
The studyconfirmedtbat the probahilityofa serieus fire in a
roadtunnel in the UK
was extremely.low.lt was concluded that, with regard to tunnel
safety, most benefit
was likel)t toaccrue fromimprovements inoperational management,
incident
planning,fire detection, conununications systems andprovision of
a means ofescape,
At present, the installation of sprinklers does not seem to he
warranted in most, if any,of theroadtunnels in theUK.
As .envisaged from the outset,a detailed programme of research
is required to
investigate the cost-effeotiveaess offire .suppeession systerns
in road tunnels. The
requirements for such a programmeare considered in this project
report.
1 INTRODUCTION
Recent serieus fires in road and rail tunnels in Europe have
focuseed attention on the
safety of road tunnels. Such events have confirrnedthe.
importanee .ofeady detection
and (appropriate) intervention, to prevent a fire from growing
to the extent thatconditioas in the tunnel become untenable for its
users and emergencyserVices.
Thisreport covers the first phase of a (proposed) three-phase
project to provide the
HighwaysAgency (HA)with adviceand recommendations. on theuseaf
fire
detectionand suppressionsystems, including spriaklers; in raad
tunnels.
Inessencc,the first phase was to provide reeemmendations on the
work programme
fortbc following phasesof theproject. lts brief was to.
invcstigate thc capabilities,
costs andbenefits. of firesuppression systemssuitable for road
tunnels in the UK. It
was alse.to cover the important and related.aspeetef'fire
dereetion.
Two sabeontractorsassisted TRL in this study:
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1 SymondsGroup was cornmissioned to define classifeations for
(a) the size
and frequency of fires in road tunnels, and (b) UK road tunnels
based on
parameters affecting the instaUationand use of fire detection
and suppression
systems within them.
2 Chiltern International Fire Ltd was commissioned to
investigate taeoperational management and modelling of fires in
road tunnel. Thisincluded a
review of the capabilities of firedetection and
suppressionsystetns that mightbeinstalled in road tunnels:each of
these was ranked through a Value
Engineering.assessment.
The subcontract reports form Volume 2 of this report.
A literature review has been andertaken to collect and assess
the resultsoffire tests in
road tunnels. Evidence was also sought from tunnel operators,
particularly these withexperiellceoftheuse offixed frresuppI'ession
systems.
A risk management studywasundertaken .a t TRL. This ranked
variousfirescenarios
forroaqtunnels in order .ofrisk basedon.the product of
anassessedcoeseqaencepriorityanda probability ofoccurrence
.priority. However, becauseoftbepaucity of
data forsuchextremelyrare eveats; thefindillgs are
tentative,
Costs were estimated for the preeurement and instaflation of
fire dereetion and
suppression systems in a lkn1longtwo~lane tunnel:this wasbasedon
designs for theStockholm. Ring Road .Tunnel. .This exercise
wascompleted for-the two .:systems
rankedhighest in.the Value Engineering assessment, ke.a
foamlwater delugesystem
andawatermistsystem (both combinedwithan opticalfibrefrre
detection device).
Conclusions are drawn on the installation of fire detection and
suppression system in
road tunnels. Recommendations are made for the werk programme
for the following
phasesofthe project. Most ofthis iscovered in Volume 3 of this
report. Further workmight modify, or even overtum,
theconclusionsofthisinitialstudy.
(The first two volumes of this project report were issued in
June 2001. Following
further study, which established the recommendationsfor
taldngthe workfurther (see
Volume 3), this now three-volume report was produced in October
2002.)
2 DEFINITIONOFFlRES
2.1 FREQlJENCY
Eires intoadtunnels are rare events: indeednocatastrophic
firehasever takenplacein a roadtunnel in tbe.UK. Theprobability ufa
frreina particwar tunnel is dependent
on sitespecificfa.ctol'Ssuchas. twmelgeometry (in .particularits
length)andthe
characteristics of the traffic flowing through it. Each tunnel
in the UK has uniquefeaMes.Nonetbeless,amean
:rateoffireoccurrencecan be.estimated from historica!
data,)frexample aSreported byBird .and Elsworth(1999) and !he
Home Office(1995).However,becauseastandardreporting system forsuch
events was not used,
the accuracy of thesedata is open te
question.Inparticwar,records weuld ner be kept
of incidents that did not come to the attention of the tunnel
operator or fire service: itcould be assumed that most of these
wouldbe relatively minorincidents.The data are
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surnmarised in Table 1. For the purposes of this study,
'serieus' fires are defined as
those that could resu1t in injuries or fatelities and/or damage
to the tunnel
infrastruetUre. Taking a (very) cautious view, these can be
assumed to represem 5% of
all fires:~is is based onthe fact thatthis percentage is
generared by vehicle
collisioas, ~d so their consequences are more likely to be
severe, Given that there are
about 20 or so road tunnels in the UK thisrate is equivalent to
a 'serieus' fire everytwo years or so. However, "serieus' fires
defined in this manner have not in practice
led to anysubstantial or prolonged disruptionof the operation of
any road tunnel in
the UK. Note that the first rood tunnel in the UK (at Blackwall)
wascommissioned in
1897 and no particular problems relating to vehicle fires have
been reported to date.
The proportion of fires that cause such disniption is probably
less than 0.1 %.
ABrepor~p
vehlcle fires
4firesperl0S vehicle.k:m (equivalent to one fire every 21 months
in
every 'average UKroad tunnel'*) .
Serleus flres
0.2 per lOS vehiele km (i.e, 5% of flres are assumed to be
serieus)
(equivalent to a serieus fire every 35 years in every 'average
UK road
tunnel'
*'Average UK road tunnel' defined as an 850m long tunnel
carrying 46,000 vehicles
per day (see Appendix B)
Table 1 Estlmated frequeney of fires in UK road tunnels
2.2 SIZE; DEVELOPMENT AND DURATION
Information O n the .types of fire expected in road tunnels has
'been obtained from
arialysis of the design data for modem tunnels, the results of
experimentsand case
studies of actual tunnel fires. Table 2 provides estimates
suitable for assessing the
requirements of fire detectionand suppression systems for
various fire loads (see
Appendix B). The data were derived from the sourees Iisted in
Table 3.
Vehicle Peek heat
output
Maximum
temperature
Fireduratlon
Ca r
Bu s
La
Hazardons load
o e
1000
1000
1200
1200
Table 2 Data for varleus classes of vehlcte flre
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Souree
BD78 MRB 2.2.9
UK FireResearch Station
Eureka Firetun EU499
Stockhohn Rin Road Tunnel
0resundTunnei
Activi
T ical values for desi
Vehicle fire tests for the Channel Tunnel Safe Unit
Vehicle fire tests in a ventilated mine all
Desi firescenarios
Desi fire senarios
Tabl 3 Sourees of data for Table 2
2.3 SPREAD
Fire sp~~d is dependent on the presence and location of
flammable material adjacentto the me. A fire might weU spread,
progressively,.through a queue of traffic backed-
up behind a buming vehiele, The rate and extent' offire spread
dependon the
following;
charaoteristics offire (size, fuel souree etc.)
position of other vehicles
characteristics of the vehicles in the queue, particularly the
loads carried by goods
ve1cles
ventiltion conditions
speed of response of effective fire suppression system
Because of the scareity of test data, the likely fire spread in
a road tunnel is difficult to
estimatewell. It is conceivable that, in the worst case,
vehicles could be stopped
either side of a fire as happened in the Mont Blanc tunnel in
1999: in this case 36vehic1eswere destroyed (see Sectien 1.2 of
Appendix A). Iris prudent toassume that
fire willspread; its. rate ofspread isdependent on the factors
listed above. Furtherdiscussignon fire spread is given in
Sectioris1,3.4 and 1.3.5of Appendix A.
3 TYPES OF TUNNELS
3.1 GEOMETRY
Each UKroad tunnel iS\1nique in .someway or other with regard to
its length,
cross-scti9l:bb)n9itl.ldin~lprofile,v~ntilation,IltUnber
aIld"Widt~of ..traffic .l~es,~d thechaiateristicsof traft1cflow.
However, forthepurposesofthis study, thetunnels can
beputiri.fu oneofthreebroad groups;
lcircu1ar bored tunnels
2 non-eireular driven tunnels
3 ethers, which include cut-end-cover, immersed tube and the
like
The features of the different groups affect the requirement for
fire detection andsuppression systems, and the practicalities of
their instellation.
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Circular bored tunnels (Flgure 1 in Appendix B)
circularbored tunnels in the UK are generally the older, longer,
sub-aqueoustunnels(e.g. Blackwall, Dartford, Tyne and Mersey)
in general, ventilation is semi-transverse
a. circtdarcross-section provides headroom above the centre of
the carriagewaybut thi~~pace is gen eraUy taken up by existing
services
thereislittle freespaee at the sides of these tunnel
oftenJhere isa. void beneath theroad deck.along the invert of
these tunnels,. butnot alwa,ysalong their fulllength;. sueb. a.void
can provide .a route for pipework
a largeproportion of the reported tunnel fires. in the.UK. were
from the Tyne andDartfordtunnels - however, these are manned and so
minor incidents are morelikely tobe reported than for unmanned
tunnels
Non-eircular driven tunnels (Figure2 in Appendix B)
these are generally shorter than the.icireular: bored tunnels
(e.g. Southwick,
RoundbiU, andSaltash)
theyhaye a greaterwidththan the circalar bored tunnels
aH areloIlgitudinally vntilated
thereisspaeeabove 'the.carriageway whichceuld aecommodate the
additienelser'\'ibesrequired for fire detection and sepprssion
systems
there i8.no void along the invert, andalthough servieetrenehes
or ducts may existben eatha walkw ay it is unlikely that these will
have much, if any, free space
Other tunnels (Figure 3 in Appendixll)
thesevaryinJength (e.g, Hatfield at 1l50m, and Fore Street at
400m)
fornewieoi1Struetion, the eross-sectional area and shape willbe
less constrainedbygeo19gical and econom ie factorsthanfor bored
tunnels
forexisting tunnels, thespace outside the traffic envelope might
be limited
longitu.Qinalventilation is the norm
shallow depthofcover
no. voidprovided along invert
3.2 DESIGN SCENARIOS
Ina~diti()~t0tunI1el.geometry,asdiscussed.
above,considerationmust begivento thedifferen:t~ffic mvements
within..uni..and .bi ..directional
.tunnels;.bothin..temlSof.the
overaUriskand .seventy ofcollisions and of operational
procedures in emergencysituations.
Sjmilarly,the difference between limited facility. tunnels
(LFT)and. standard height
tunnelsllas implieations ..for likely. fire
.:scenariosand,therefore, for det~etionandsuppression eptions.
Despite proven utility .else",here, for. example in .Fraace
(seeAppendix T ) , there are no limited facility road tunnels
in"the UK but, because they
might beibuilt in future, they are con8ideredbnefly .herein,
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3.2.1 Uni-and bl-directionaltunnels
Most, but not all, UK road tunnels carry uni-directieaal
traffic, However, where thetunnel remains in service during
maintenance, the traffic will be bi-directional.
Bi-direetional flow increases the risk and severity
of'collisions, and the eonsequencesof a fire, Beeause there is
likely to be stationary traffic on bath sides of acollision,
with.bi-directional traffic smoke cannot be removed in .any one
direction away fromall thetunnel occupants.lt is. clear that the
mitigation of the risk of a majorfirethroughthe use of detection
.and suppressionsystems is more urgent where traffic is
bi-directional.It is cruciailo note thatthe latter was the case
in boththeMont BlancandTauetrn tunnels (seeSection 1.2 of
Appendix.A).
3.2.2 Limitedfacilitytunnels
The hearoom in a LFT and the size and types of vehieles using
suehtunnels affect
the requrements for heat detection and fire suppression systems.
For example, for aparticularfire load thelemperature rise at
ceiling level would.beexpecsed to be higherin a LFT thana
standard-height tunnel. Dereetion systems migbt therefore
beexpected to be more effeetive. in a LFT in terms of their speed
and.eccuraey of
detection, When assessing the risk of fire in an LFT, itSh9uld
alsobeappreciated thatlarge.gQodsvehicles, buses and m9st,
.ifnotall, hazardons leads would be.excludedfrom them and also that
the traffic flow wouldbe uni-direetional. Further diseussionon
thist9pic is provided in.Sectio 2 of Appendix A.
4 OPERATIONAL MANAGEMENT
The eXJ?frience.gainedof fires in tunnels has shown the
importanee of early dereetionand (appropriate) intervention to
prevent a fire from growing to such a level thatconditions in the
tunnel becom dangerous, if not life-threaterring, for its users
andemergency service persennel. Altheugh the available fire
suppression ...system can
provide 'a first response, at present they are incapable' of
extinguishingaU types oftunnel fire. Intervention by the fire
service is therefore necessary to dealwith firesoutsidethe
capabilities of such systems. Henee the eerly and .accurate
detection of a
fire are cruelal requirements even where a permanent suppression
system is installed.
The benefits of automatic dereetion and suppression will only be
realised as part of ani!1te~t~ .~ppr~c~
to.fire.safety....S\lc:banappraach.s~0tll~.Start .b y
.e?e$idering.themeansofreducing
.the.riskofvehicle.collisions,..whichmightbethesoUfceof.fires;Safetysystems
must be considered inthe round. Theusefulness of anautomatic
fire
detection system is dependent onother systems being in plaee to
respend to itsalarnlS,Likewise,. suppression systems
IDtlstbe.eonsidered as part.of a.fire proteetionsystem,.which
in.cludes ventilation control, traffic managementand the provision
ofescaper()utes. Tbc viabilityofsafetysystemsmight be dependent on
whetherornot
thetunll~l bas a permanently manned control room.
Equipment and procedures must remain effectivethroughout
theworking Iife of the
tunnel, thus consideration must be given to maintenance of the
equipment, training,and updating and reviewing operational
procedures.
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The policyrcgarding the passageof hazardous goods through a road
tunnel(s) should
also be considered. And, on an even wider scale, Central
Government, perhaps in
collaboration with the haulage industry, might examine the means
of preventing fires
arising from vehicle defects as part of a broad safety
strategy.
Operators must be prepared for dealing with emergencies: advice
on such matters isgiven by Bird et al (2001) and by BD 78/99 (DMRB
2.2.9)t. The strategy for dealing
with an emergency should be based, as faras pessible, on
standerdprocedures,
4.1DETECTION OF FIRES
In most cases, automatic detection equipment, utilising remote
sensors er image
analysis, Will provide the earliest notification of a fire to a
tunnel operator. However
other sources should not be overlooked,these inelude detection
throughclose circuit
television(CCTV) images, and by members of the public
usingemergency er mobile
telephcnesor by triggering the alarm on fire fighting equipment.
Although an alarm
willbetelvd ineither a tunnel er police control room, depending
whetherthetunnel is>rnanned or uamenned, telephone callsby the
public ..may be received
elsewheretThe procedures and training foroperators sbould,
therefore,anticipatea
variety of'possibly conflicting alarms, Consideration should be
given in planning and
tra:.ningJ? the Iikelihood of false alarms from each source, but
in particular from
automaticequipment Procedures should include confirmation of a
fire through, for
example,
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This might include altering ventilation settings (but see above)
and starting or
stoppingifire suppression equipment, It is imperative that the
fire officersattending an
ineident.sre conversant with the layont and eperation ofthe
tunnel through on-site
training and familiarisationexercises.
4.4AFTERAN INCIDENT
The proeeduresfor retuming the tunnel te fulloperation include
the restoration of fire
detectioand suppression equipment, for example re-filling tanks,
and the clearance
of debrisineluding any remaining :fire suppressionproducts. It
wouldalsobe useful in
planningfor future potentlal events if detailed records were
kept of the incident and
response$(see Section4.7).
4.5 TJAjNING, EMERGENCYEXERCISES, SAFETY
MANAGEMENTANDREVIEWPROCEDURES
Becauseof the .aeed for a .rapid and .appropriate response
foUowing. the receipt ofpossiblyivariedand conf1ictingalarms,.
operating staff should be able tocope with
emergeticysituationsand they must be trained in .the operation
of fire detection.aad
suppressiPll.equipment.
Experien.ce. of tunnel fires,partieulai'ly these .in ..the Mont
Blanc a.nd Tauern.. (see
Sectionj,2 of Appendix A),. shows that. gQodeommunication is a.
pre ..requisite .for
safety.insuehevents. To ensure an integrated
and.effectiveresponse, tunnel.operators
and emergency services should be fuUy aware of the procedures,
equipment and
capabilities of all parties likely te be involyed in taekling
afire, Thus plans for the
activatien. of fire suppression systems should beestablished
through round-table
discussions, ..andsimulation exereises are. necessaryto
testthata .eo...ordinatedapproachcan be achieved in the event of a
fire, Althougb theoperation of automatic
detectionequipment can be simulated withease, consideration
should be given to the
feasibilityof operating suppressionequipmentduring
suchexercises.
Thereareinstances where failings in managementand operating
procedures have
impairedthe response to a tunnel fire.
Therefore,proceduresshouldbe .in.place for
overseeing, co-ordinating and regularly. reviewing. the
operation and maintenanee of
equipment and contingency plans for dealing with emergencies: it
is imperative that
proeedllteS,personnel andeqtiipment. are .appropriate to thewk
inhand. General
guidance on tunnel procedures is givenby Bird et al(2001).
4.6 OPERATION OFFIRESUPPRESSIONEQUIPi\fENT
The operation of :fire suppression equipment is, in
itself,dangerous, particularly
followinga. false a1ann ...Hazards include reduced. visibility,
.slippery road and
paveinentsurfaces,. andpanic.AIso, where a firehas occurred,the
activation offire
suppressionequipment at the wrong location mighthamper those
melding the fire and
disrupttheevaeuation of the tunneL
Theprbabilities andconsequencesoffalse alarms shouldbeevaluated
when
considering the use of
automatieallytriggeredfiresuppressionequipment. Beeauseef
the serieus consequences resulting from the operatien of
suppression systems (that arecurrently available) in response to a
false alarm, it is improbable thet automatic
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activatien will he acceptable: this situation is unlikely to
change for some time. Thus
it followsthat fire suppression equipment should only be
installed where there are
staff available 24-hours a day, who are trained and able te make
the necessary rapid
appraisal and accurate response (i.e. where there is a control
room). Where no staff
are on site, consideration may be given to the opertion of
theequipment froma
regionaltraffic control centre or, possibly, a fire service
control room. However,unlessthecontrol room isconnected to CCTV
eameras in thetunnel itis unlikely that
the cOrrectresponse wouldalways be made. Purthermore; unlessa
fire station is close
te the mflnel some of theadvantages of immediate detection
arelost.
In Sweden, a 30 to 60 secend delay is allowed befere a
suppression system is
activated.This is to allow a check to be made for false alarms
and to verify conditions
inthe tunnel, butthis reqUiresa rapid interventioll and
appraisal by the operator.This
policy>assumesthat, .overall, tbe advantages .of .correct
manul operation might
outweiglttheadvantages of onlya slightly faster (automatic)
response witbtbe
attendantproblems of false alanns.
Guidelinesshould bedrawn up te assist operators in making
decisions aboutthe
operationoffire suppression equipment. The decisien-making
proeess isaffected by:
trafflcfiow - whether moving or statienary
loationof pedestrians (evacuees, tunnel operatives and
"fire-fghters)
whether any warning of a change in eperafion can be given
acu.racy ofthe location ofthe fire - forexample, whether
visibleon CCTV
I1~tJ.lreand .extentof fire - whether growiag or threatening
lifeand/or the
~elinfrastructure,and .whether otberfires might. develop:
through, .for
e~ple, multiple. collistons or fuel spiUs
whetherfire service persennel are present
Clearly ,thesupply of water, or other agents, for fire
suppression should be adequate,
with su.fficient reserve, to deal witb tbe fires for wbich
tbeequipment is designed, The
supplysbould ..be independent of nd not affect ather .fire
fighting supplies. The
required stock is influenced by the likely speed of the response
of th fire services and
also by the type of their equipment. In Japan, a tunnel fire was
controlled for 30
minutes or sobefore on-site supplies were exhausted; the fire
re-ignited befere the fire
services apived (see Seetien 1.2.4 of Appendix A).
W1l~J,"~~ fit~.supprys~i()I1.sY~YII1i~.~H,ll~
il:l.l,l;.t9IlI1yl,
thy.4fl,l;in~gy.sY~~II1~()\lld.l>esiZedand>adapted
accordingly, .inparticular t~ prevent .the. releaseofhazardous
materialsinto the environment. The procedures tobe foUowed
intbeevent. of theoperatics .of a suppression system shonld include
the rnobilisation of facilities or
equipment to disperse suppression agents or products.
Fire detection and automatic suppression equipment ..should
function .as intended
throughout the eperating life of a tunnel.' (At tbe time ofthe
recent {rre in tbe Mont
Blanc tunnel, part of the suppression system was disabled.
formaintenance but there
was no back up in place.) Equipment should he reliable and
robust: it must he able tocope with the aggressive environment
within a road tunnel, Guidance on equipping
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tunnels is given by Evans et al (2001). To facilitate
maintenance, and retrofitting to anexisting.tunnel, equipment
should beeasy to install and access. There should he somemeans
oftestingequipment to obtain an assurance of its condition,
4.7 INCIDENT RECORDS
Recorqsof fires andother incideatsareessential datafor
determining the probabilityofcertaineventsoccurring during .the
service .Iife of a .tunnel,andhence for. makingdecisions on the
installation of fire detection.and. othersafety equipment.
Theycan
providesalutatory lessens about the need for and the
effeotiveness of eperating andemergency procedures.
Incidelltreords from tunnel operatQrs,police, fire brig~desand
other bodieshavebeenass~ll1bledfor 14roadtunnels in
EnglandandWales.The resultsare reported.byBirdap,d E1sw0rth (1999)
and areutilised in AppendixB ofthis report. Using
thesedataanattempt was made to derive statistieally based stimates:
oftheoccurrence of
incidents. However, it was concluded that variabie standerds of
reporting made itin1pQ$Sibletoestablish reliabie trends. ft. is
recornrnened that, as part of tbe routineduties,itunnel operators
log specified hazardous iaeidents.: incorporating, whereapprQpnate,
records from the emergency services ".Sueh logs shouid. provide a r
u ndescription of the incidente and review what, if any ,changes
should he made toopera.til$procedures ..Thisshouldprovide.
comprehensive .and .consistent records oftunnel. incidents for
future evaluatioa,
Experience of usingthe STATS19 (DETR 1999) road traffic accident
databasesuggested thatthe generation and storage of natioal
records, to an ad:quate andconsistent staedard; required the:
creation ofanational. overseeing body made up of
represeatatives from the providers, users and managers ofthe
data:see Bird et al(2001). The tunnel operators'
meetingsintheUKmightprovidean appropriate forumfor developing a
national system of record keeping for tunnels.
BD53(DMRB3J.6) details the records thatshould.bekept by tunnel
operatcrs.Forutility,such records should be comprehensiveandkept
up-tc-date, In a well-collatedand readi1y aecssible format, such
records would form au invaluab1easset forundert~g risk
analyses.
5 OBJECTIVES OF FlRE SUPPRESSIONSYSTEMS
1'0 . a p P 1 1 s
.thepotentiid.of.ire.sppressil1.sfgtmsitis.neessrY..tocnsidertheob]ectivesoftlleir
use. Eight leey .functional objectives have been identified
andrankediIJ.ti1e following order of priority.
1 Safety of road users (includingpedestrians)
2 Safetyofemergency service personnel
3 Sa.fetyoftunnel operatiVeslcontractors
4 Proteetion of'the tunnel structure
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6.3 SPRINKLER SYSTEMS
All butene of the systems ranked in Table 5 is based on the use
of water witb or
withoutadditives er foams, AUwater-based systems require
delivery to the loeationoftbe fite,.which conventionally would be
via nozzles supplied by pipework and
valves,
Experiments have been undertaken to. test.theeffeetivenessof
sprinkler system.sonhydrocarbon pool mes of a size that simulate a
vehicle fire, However, information
about theconfiguration used in these ex.periments is incomplete
and there: is littleex.perimentalevidence to identify the optimum
location and type of nozzles.
Sprinkletsystemsare mostoften rnouatedat eeiling level. in
.puildings; .this bas the
advantagetbat water distribution.is assisted by gravity,
However, as confinned by
tests carried out by the Fire Research Station (FRS) forthe
Channel TunnelSafetyUnit,afweunderthe bonnet ofa ear, or in its
interior or.ben.eathit (wIlere leak;,edfuel
will ignite) is shelteredfreman overhead sprinklers (SeeAppendix
B Sectien 2).
The ex.periments undertaken at the Memorial Tunnel included
tests of foam-water
(3%.AFFF) sprinklers:onhydrocarbonpool firesef up to .1OOMW.The
effectiveness
ofceiling-mounted sprinklers, at a height of4.3m, was unaffected
byanairflow of4.2rn/st1'm>ughthe tunnel. Nozzles mounted on the
tunnel wall, at a height of 2.1m,
were found tobe Iess effective, However, this finding mighthave
more tedo with
variations in the size of the fires and the rate of discharge of
the suppressant than the
position of the nozzles.
The discharge of a low-expansion foam at a lew-level in a tunnel
might be very
effectivein sappressing the combustion of spilt fuel, but
mightbe ineffective wherethe fire involved the payload of a goeds
vehicle: the fire at the Mont Blanc tunnel
involveda cargo of margarine and fleur (see Appendix A, Section
1.2.7 and Appendix.
B, Section 2, page BW) .
In.general, tbe. discharge.from a lew-level nozzle will cover a
.smaller. area than a
simil~rone .positioned onthe ceiling. Lew-tevel ..placement
mightprovidesomereduetiQninthe length ofpipework and.ease of
inspection and maintenance, but it. is,
therefor~, likely torequirecloser nozzle spacing. The
installationofupward-spraying
nozzlesin tbc rood snee, inana~lllPt. toovercome .the .masking
effect
ofb~d)')"grk,.is.at..present.tb01Jg;ht.t().be.iIIlpr~ctieal..beca~se..(a)
.~f.the.obstrtletion.to.thepaveIn~nland (b) such nozzles wiU become
blocked quiterapidlyandbedifficultto
maintainor replace.
6.4 PIPEWORK
Consideration must be given te the protection of pipework in the
aggressive tunnel
environment, and to the possible advesse reaction ofthe pipework
to itscontents.For
example, because of the latter, the pipes for a foam
distribution system cannot begalvatlised. Thus relativelYexpensive
stainless steel pipes and fittings might have to
be usedin a tunnel. For. frostprotection,. pipework .mi~ht need
to. beprovided witbtrace heating. Provision must be made for the
dismantling and replaeement of lengtas
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of pipe; where flanged pipesare used this might require the
introduetion of bends orspecial joints.
Based on the specificatien outlined in Sectien 9.1 below, and as
detailed in Section3.3.13 of Appendix A, there wiUalmost certainly
be spaeeto install spray heads and
pipeworkin a tunnel, buteo-ordiaatioe with Iightlng and wiring
systems may becomplex.To meet the. specificatioa; separate. water
and foam .eoaeentrase distributorpipes running the whole length of
the tunnel are required: 200mm and 65mm diameterpipes would be
required respeetively. Motorised valves to mix the water
andconcentrte and te feedthemixinto risersare also required,
Wherethevoid beneaththe road deck is used forventilation, it
still rnight be best torun the .pipes along them ..There .should be
sufficientspace for the pipes .andassooiatd valves, and any
consequent rednetion in the performance of the
ventilationsystenlc~uld he.corrected. hyintroduc.ing jet fans to
boost longitudinalairflow .:TheinstaUatiBnofjet fans
wouldalsohnprovethe.control ofsmoke wheretraffic flow is
uni~diretionaL However, the void rnightnotrun alongtheentire
lengthofa tunnel, Inthis aS,and .also for mmersed tube and
non.circular bored tuanets, the only freespace fotthepipeworkand
valves mightbe above a walkway, at say 3 10 4m abovethe invert.
However:
1 E&ra circular er arched structure, this wouldprobably
coineide withtheminimum distancebetween the
trafficclearanceenvelope and the tunnel wall,
2 Cmmonly, suchspaee is used for ether mechanicaland electrical
equipment.
3 The main pipework and valves are vulnerable to theeffects ofa
fire .and,
therefore, require proteetion.
4 Similarly, pipework mounted on a tunnel waU might require
protectionagainstvehicle impacts.
5 The weight of the pipework, and its contents, impose a lead on
the tunnelliaing.
Theremightbe room to run the mainpipework in.the crown of a
tunnel, particularlyincircular and .arched ..tunnels. However,.
here, the pipework and. valves would bedifficllittoaccess for
inspection .and maintenance,and they might become detachedwhen tile
tUnnel Iining WaSdamaged byfire~. Where ..available, ir might be
.possible torun thetp,ain pipework into a tunnel via ventilation
shafts.
::" ::< :,:> < :,:-:":::" ::::> ::: .. ' ::: .. '
,., :.. :: : ',., .,' ,., .. ,. , ,-:.::'. ::::,:,. ., ,.,"""," '"
, , , ..
In additiBIlt() thein-tuIlneleql1pment, ~\Vatertimk and
associatedpllmps are required
outsidea tunnel. Finding space for the pumps should net he a
problm,' but it might hedifficultto find sufficient space adjacent
to the tunnel for a large watertank. Sometunnel approaches are
eenstrucred on reclaimed or made ground, and in these
casessubstanti~lJoundationsmight berequiredto support the weight of
thefiUedtank.
6.5 DRAINAGE
The drainage systemof a tunnel must be capable ofhandling
thevolume of water thatcould be discharged by the spray beads; a
flowrate .of just over 4,000.litres/minute or70 litres/sec could be
assumed (see Appendix A). This is not far from the commonly
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used design figure of 66 litres/sec, which is based on the
output of two firehydrantseperating simultaneously (see BD78;
Clause 7.32). However, where separate
supplysystemsa.reoperated,asmaybethecase when asuppression system
is retrofitted intoa tunnel,~ere is a riskofflooding when both are
operated simultaneously for morethan aboutlOminutes,even in atunnel
provided .with a modem drainage system. The
drainagesystems .in older tunnels might not beable to cope with
suchhigh flows, andspace mayrestrict the size.of pumps. that ean be
installed inthem .{Howevermostdrainagesystems
areover~designed;).Increasing the sizeofsumps in a
tuanel.eouldbevery costlyif, indeed, it was practical.
In mostn9rmal.situations, .the flooding of a..tunnel in the
event of a fire. would beunaccepta{)le. Attheveryleastaccess to the
fire would he made.rnore.difficult andevacuatietrof vehicle
occupants, particularly the young, elderlyanddisabled,.
fromthetunnel willbe hindered (perhaps fataHy so). At worst,
flammabl substances could bespreadbey6ndthe area over which
thesprinlders are operating .aad hazardousJiquidswithinthesumps
couldbe released. !he capacityofthe sumpsand the drain~ge
pumps must be.assessed when considering the instaUation of a
sprinkler. system .inatunnel: indeed they might determine the
viabilityofsuch a system.
It shoutdbeappreciated that most drainage pumpiagsystems. will
shut down when ahazardouelsabstance is detected in a sump: this
would 1000 the pumping capability atthat sump'The spillage of
aliquidhydrocarbon followed by a fire would therefore bea very
diffieult situation to address satisfactorily.
6.6PRIORITIES FOR FURTHER RESEARCH
Theranlcil1gofthe variousdetection and suppression systems,in
Table 5,provides a
basis forprioritising further research on the development of
appropriate fixedsuppression systems for tunnels with
bi-directional and uni-directieaal traffic'lows.
With firedetection systems, further research seems warranted on
linear heatdetectionbased onoptical fibre technology. Optical flame
and smoke technologies, .combinedwith CCTV digital imaging, appear
to have. the necessary. performance attributes.Common to all these
systems is the availability of intelligent signal processing. It
isconsid~redthat these arethe most. likely routes for developing.
robust fire. detectionsystems foruni-directionalandbi-directional
tunnels,and ones that will work inconceI'twithautomatic fire
suppression.
Systems based on water spray and water mist, or combinations
with these, seem-t o
ll~Y~tJ : 1 .~ !~t~t .p~tell~l .f()r.~~t()trlatic..~re
..sHP~ression ..~.~~t:rns'...VV~ter.rnist..s}'st:rnsare.
inreasingly promoted foruse in
transporttunnels,buttodatlittleex~rin1entalworkJ.la.speen.
carriedOtlt. to validate the .clain1sand theoriesput forwardfor
them.ThissllQllldbe ad
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6.7 FULL-SCALE TESTS
STUV Aisthe German research organisation for underground
traasportetien facilities,
Theyhav recently stated that they intend to establisha fire test
facility ineither an
existingtunne10r ina purpose-bu1t tunnel up to500 te 600m long.
They propose to
undertakefull-scale trials of all. types of automatic fire
detection and .suppressionequipment. The totaloost
oftbeexperimentalprogrammeis estimatedat 2.2MEuro,
onthebasis tbat suppliers would provide and insta.lLequipment
free of charge. The
locationef the test facility was to be seleeted in mid-200 1 se
tbat the sitecan be
preparedduring the secend half of the year. The first ful-seale
tests were planned to
takepla.ceduringthe flI'Sthalfof2002. The Swiss Roadand Railway
Administrations
are likelyto be support STUV A in tros work, but STUV A
areseeking the support and
collabo'flil,tionofother parties.
The N(1)VegianFireResearch. Laberatory (NBL) is the Norwegian.
ceatre for fire
technology resrchaad developmenLln May 2001 it infonned TRL that
.it was
bidding>for anEU-supported project on .firesafety in tunnels.
TRL. anderstand thatNBL ha$the following felities for undertaking.
full-scale-triels,
1 1l.100m long concretetnnnel; whichcan be used to train. fire
fighters,and
2 tWo roadtunnls, 800 and 1600m long, wbich are.not used for.
ordinarytraffic
and are better suited for undertakingfull-scale trials.
The Hagerbach Test Gallery Ltd, loctedin'Flums.Switzerlend is
censtnicting;
1 a~OOm long two-lane motorway tunnel, withacross-sctional area
of 80 to
90Ill,
2 in.clinedtunnels at gradients of 5 and 10%, each with a
cross-sectional area of
50m2,and
3 atunnelhaving a cross-sectional area of 40m2
These. tunnels are tobe used fortraining emergency service
personnel. intackling
tunnel fires, It would seem that such a facility would ..be
ideal.forcarrying out fuU-
scale fire suppression tests. It is believed that this is one of
the tunnels is being
considere4for useby STUVA.
The~~handSafetyExecutive(HSE)ihaveasubsJgfacegan(;)rya11ds\U'face>test
galleryattheir .laboratory nearBuxton. Thesub-surface. gaUery
.is200m Jong but it
has across-s(;)Ction~Lar~ of4.2n12 l11akingit unsuitable for
fuU-seale tests. of tunnel
fires.Tbe surface gal1ery is 366m longand has a slightly largeI'
cross-sectionalarea of
5.6m2,but againit isJar toe smal1 for fuU-scale fire tests,
except possibly for LFT.
7 COMPUTER MODELhlNG
As part of this or ether projects, it is probable that future
fire tests will he eerried out
on suppression systems based on, for example, water mist
teehnology, Because of the
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high eests-of full-scale tests, it is attractive to supplement
the physical data obtained
from these with the results of calculations. However, there is
little published
information that could be used to validate the results obtained
from computation fluid
dynamic (CPD) modelling of tunnel fires. The validatien of sueh
calculations, by data
obtained from suppression experiments, win enable 'virtual
tests' tobe carried out
relativelycheaply. Such tests could check the sensitivity of a
design tovariation in tbe
governing parameters.
The application ofCFD models to, for example, the Memorial
Tunnel test programme
baveshowa that they are capable of predieting, with a
reasonabledegree of accuracy,
the air flows generated by a fire and the influence of.
featuressuch as powered
ventilatioJl. To be of benefit to a designer, the CFD models
need to be able to account
for the action of a suppressant on a fire.
The use of computer modelling for prediering the effects of fire
suppressants was
assessedbyconsidering the .abilityof .eight CFD models to
provide informatica
relatingWtbirteencriteria including the following five
criticalones;
I atmospheric tempersture
2 s11l(}kedensity
3 visibility (including effects of smoke de-stratification)
4 relative humidity
5 di~placement of fire gases by thegeneration of steam
Theresultsoftheassessment are presented in .Seetion 3.5 of
Appendix A and are
summarised in Table 6.
CFDmodel Past use in tunnel
applications
Validation wlth
respeetlo tunnel
flres
'TUNFIRE
P H O E N I C S
STAR
Sot . ;vENT
GAMBITtr~
GRm
F L O V E N ' f
FLOW3D
CFX
Analytical
treatwent of
interactioo.between
su ressantand lirev
v
X
N o re s ..oase re eeiv ed
X
X
X
X
TabJe6 AssessmeotofCFD medels
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General. recommendations can be made regarding the
instrumentation required to
providedata against whieh the predictions derived from the
models can be judged,
Instrumentation is required to monitor:
rate ofmass loss of fuel
airlsmoke flow velocity atmosphere temperatere
visibility
humidity
eoncemtrations of fuel gas and OXygen
the deposition and/or density profile of the suppressant
8 RISK MANAGEMENT
Risk assessment is a structured approach that improves
theconsistency of deelsion
making and the cost-effectiveness in the allocation of
resources. His the corner stone
of all harmonised health and safety legislation and
standerds.
A riskassessment indicates; systematically, how hazards can
occur and provide a
clearer understanding of their nature and eonsequenees
(including economie ones),
thereby improving the identification of the most effective way
to prevent injury or
damage to health.
The flowchart in Appendix C outlines the broad framework for
risk assessment, The
process iavolves consideration of the technique most appropriate
for the partienlar
assessment, Techniques range from basic qualitative methods of
hazard identification
and anal)'sis to advanced quantitative methods in which
numerical valnes of risk
frequency or probability are derived. Because adequate
quantitative. data on the
probabilities of the individnal risks are not available,
qualitative techniques have been
used in this study. An assessment has been conducted on three
different classes of
tunnel, for seven types of fire.
The resultsof the assessmentsuggest that the most likely fire
will involve a single car.
The fire/with the worst consequences is likely to be .generated
by a multiple cellisionwithatJ~st ene of the vehicles carrying a
hazardous load, They also snggest that a
fire occurrlng in a circular bored road tunnel is likely to have
the most severe
conseq1}~ces;these tunnels are, in the main, the.older
sub-aqueous tunnels withsemi-
transvegie ventilation and Hmitedescape facilities. Some also
have bi.directional
trafficf1pw.Notethatduringmaintenancework,thetraffic
...intunnels~tretnain
operational wiIl be bi-directional.
It is cOIlcludedthat the risks posed by a fire in a road tunnel
would be mosteffectively
reducedthrough a combination of safe systems of work,
appropriate tunnel design. and
engineering control. In this context, en~ineering. control
includes deteetien,
communication and traffic eentrolsystems; provisionofa means of
escape. as weil as
fixed fire suppression systems. (A fuller di~cussion is provided
in Appendix C along
with the generio model of the risk assessment process for tunnel
fires.)
A risk assessment should he completed before any control
measures are implemented
in a partienlar tunnel. Information on the control measures
already in place, the speed
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of response to emergencies, evacuation procedures, dimensionsof
the tunnel and
characteristics of the traffic should be collected and used into
an assessment. The
probabiUtyof occurrence should becalculated for each event on
the tree pathand the
final proba.bility established for all consequences. All risks
should he quantified and a
decision made as to whether their level is tolerable.
9 eOSTS ANDBENEFITS
Althoughinformation is .available on the costs of installing
fire detection and
suppressionsystems, the benefits of suehsystemsare
muchmoredifficult to quantify.
It should b. appreciated, however, thatover~riding political
decisions take preeedenee
over theresults ofsuch a paper exereise,
As.hasbeendemonstrated.by the recellt mes in. tunnels at Mont
.Blanc, Tauefn (see
SectionJ.2ofAppendix A),andKaprun {Hamer; 20(0), the cost of a
fire in terms ofhumanlifevdamagetoatunneLstructureand
lossofservicecan be veryhigh. The
probabilityofsuch anextreme event occurring ina road tunnel in
theUK, where most
tunnels,ar~shortand uni-directional, is unquantifiably smalt
As stated.arlier, to date there has not been a catastrophic fire
in a raad tunnel in the
UK. Butdisasters and complaceney are no strasgers. The cost of
doingnothing to
improve. safety should be judged. against the consequences of.
such, thankfully, .rare
catastrophes. Inaddition to the .less oflife. and .vehicles, the
Mont Blanc tunnel: is still
out of service some two years after the fire: the alternative
route represents a.diverslon
of some 50 km, part of which is through urbanareas where the
passage of goods
vehieles isunwelcome. The fire in the Channel Tunnel
(see.Appendix A.,. Section1.2.6) disrupted services for about six
months or so, and ..in addition to. thecost of
repair there was a reduction in operating revenue for somewhat
longer than the repair
work, as user-confidence had to be regained. Finally, when all
done and dusted, it is
unlikely that the total cost of the rail crash at Hatfield, in
which 4 lives were lost, will
be lesSthan!l Billion.
There isalso the question of liability.Where sprinklers
areinstalled, the tunnel
operator/flre service must decide whether or net the system
should beactivated in a
particldar incident. If it is subsequently shown that the
decision was in error, it is
possiblthat the.owners, operators and emergency services might
.be. sued for
dama~s'In thecaseof.thefire.atthe .Digital Equipment
Corporation's offices
in:a~itl~~~~itl1990,thefire()tf1ceriAc~esllllt
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9.1 BENCHMARK COSTS
Benchrnark costs have been determined for the installation of
two fire suppression
systems,both eontrelled by an optical Iinear heat detection
device, withina single-bore two-lane 1km long road tunnel.
The teehuical specificatien for the system is given in Section
3.3.13 of Appendix A.
The hydraulic design of a system conforming to the specificatien
was completed, and
the prirnary components of the system were identified. The
.design details were
forwarded 10. a fire engineering company speeialising in the
designand supply of fire
suppres~ionsystents. Theyprovidedestimates .for (a) anoverhe.ad
sprinkler.system,
whichus~da 3% ARC foamadditive, and(b) .a high-pressure water
mist system.Similarly;suppliersoffire detection equipmentprovideda
budgetcost for thesupply,
instaUationand commissioning of. an optical linear heat
detection system. The
estiInatsare provided in Table 7.Theestimates. are based o~ the
use of galvanisedpipe\y()rkfor. the watermainandd.istribution
pipes,and blacksteel.pipework for the
separat~to~mdeliverymain. Section
6.4suggeststbatstainless-steel.pipework. mayb n~es~a.rr to
combat.tbe ag~essivetunnel environment. The
additionalcapitalcost
is likelytobe benveen ~O.5to~l miUionperkilometerofbore.However,
the low..
maintenance nature of correctly specified stainless steel should
reduce maintenanceand refiltbishment costs in future years, thereby
redueing ..the whole life casts (see
Section.~.2)-
Detectiofisstem: 'Fibrolaser IJ' er tieal linear heat deseetion
~31k
~760k
~950k
'rable7 Benclunarkcosts for lkm longtwin-bore two-lane
tunnel
Note that the above cover the eest of installieg the meehaaical
and electricalequipment, except wiring, in a new tunnel, The cost
of providing a water tank and
pumps outside one end of the tunnel is included, but net .:any
civil engineeringcollsttUctioncosts.
All all0v.rancefortheadjustmentlrelocation ofexis.tillg
installations andequipment
must be included whenconside.ring .retrofittingasygte.m
intoanexisting tunnel.Be9~H~\s~I1\yprk'1VQ~
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Escape .facilities canalso he provided by cross passages and
doms conneering the two
bores of a uni-directionaltunnel. Where the doors are in a
narrow dividing wan
hetweentwo bores it seems imperative that the doors should not
be operared until
traffic inthe ether, bore has been stopped,
BD78 l"equires that thenominal spacing between such doms should
be no more than150m~2U'1dpreferentially lOOm. Thelatter
distancecould he maintained where cross
passagesconnect te anescape/service tunnel, hutan even
closerspacing ofsay. 40m
t050m1'n.ight be desirable in many cases. And, for a shallow
urban or rural tunnel, the
possihility of providingescape routes to the surface at simdar
intervals should be
considered.
10.3 TUNNEL OPERATION
The personnel responsible for the eperation of a tunnel, whether
local operators, the
emergencyservices or a regioaal control centre,
shouldbetrained,andprepared, to
respondcorrectly to a fire in the tunnel. Where co-erdination is
required betweenoperatorsand emergency services, theprotocols for
this shold: be clearly defined,
Emergencyproceduresshouldbe clearlystatedand regularly tested by
means offuU-
scaleex:ercises during tunnelmaintenance closures, This wou1d
melude-the mannel
use ofcemmunioation and control systems,portable suppression
equipmentaad fixed
equipment such as sprinklers if fitted. This process .may
include the use of smoke
generatoJ:s,or even a. controlled fire,totesttheeffectiveness of
ventilation control.
Experietlce in such matters has shown that what should work
according to theory does
not always work as wen in practice.
10.4 PRIORITIESFOLLOWING TUE OUTBREAK OF A FlRE
The priorities for miniruising the severity of a fire are;
earlydetection and accurate loeation of fire
llotificationof emergeacy services
prevention of vehicles entering the tunnel
apprepriate setting of ventilation
evacuation of fire zone
opera.tion ofsuppression equipment infire zone
Success1'tdinlplementation of theearlier actions will in. most
cases eliminare the need
for lateractions .
............. , .
All theallthorities .consulted as part phase of the project
agreed thatsprinklers
shouldbe considered as a last resort: they were only to be used.
following
evacuation of the fire zone, and must not be triggered
automatically.
10.S PROBABILITIES, COSTS ANDBENEFITS
Tbe prol:>ability of a>catastrophic t1reoccurringin a
UKroadtunnel is.extremely
smaU, but the costof installinga firesuppression sygtems in a
tunnel is high,
Particul~lrly .for existing tunnels. Thus thehenefits of
instaUing fixed suppression
equipment in most tunnels are unlikely to be jusrifled on cost
grounds alone.iThere
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might, ho~ever, be a case for instelling such a system in the
mostpetentially
hazardons tunnels: these include the older sub-aqueous tunnels,
where their bends and
gradient increase the risk of vehicle collisions, and which have
limited means of
escape. Some also have two-waytraffic. There might alse be a
case for fixedsuppression equipment in very long tunnels,
particularly if the response time of the
emergelly services jsIikely to be more than.a few minutes.
However,the unanimousview oftl1ose .consultedwas that sneh systems
should not be installed unless there wasa
peI'1lUlllelldy-mannedcontrol room with well-trained staffabie to
assessthe severity
of anyincident that might lead toa me.
On theoJh,erhand, the eest of installing improved detection
systems would be
relativelylow and relatively straightforwardeven in existing
tunnels. Where tunnels
are monitred sueh systems.eeuld faeilitate arapid response,
aUowing the majority offires to be eontrolled without the need for
fixedsuppression equiprnent However,
although the systems described in this report show promise, none
have beenadequately proven in a tunnel fire: proving trials are
thereforerequired.
11 RECOMMENDATIONS
The folloWingrecommendatiens shouldbeconsidered in drawing up
the specificatienfor the relllaining phases of the project.
Reference shouldalso be made to Volume 3of thisprbject report when
considering further.work.
11.1 CASESTUDIES
A smallnumber of tunnel categories were defined forgeneric risk
assessmentpurposes,buttbere was considerablediversity within each
of the categories. It mightbe heneficial to undertake amoredetailed
study of a partienlar tunnel(s) judgedto be
of a relatively high risk to determine the relative oost/benefit
ratios of variousimprovements to fire safety.
11.2 COMMUNICATION AND EVACUATION
Effective communication with the occupants of vehicles in a
tunnel isareeognised
problem and it should be the target of further research. In a
number of incidents, the
response of the tunnel operator and vehicle occupants has been
inappropriate, for
example at Hstfield (Hertfordshire Constabulary, 1989): this has
increased theseverityof'an incident.
Theevacuation of a tunnel requires aneffective means of stopping
the traffic entering
a tunnel but, currently, many tunnels have no such meaes. In
many documented casestraffic bas continued to enter a tunnel
following the start of an incident, thereby
increasing the hazard and obstrueting access by the emergency
services. Provision ofgates simUartothoseused forrailway crossings
or asused atthe Clyde Tunnelmight
beappropriate.
A driving simulator could be used as part of a preliminary
investigation into means of
coatrolling traffic in tunnels. Simnlation techniques could also
be used to investigateeffective means of communicating with the
occupants of vehicles in a tunnel: these
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Symonds Group and Mr J Lavender of Chiltern International Fire,
who all assistedwith the work.
