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International tunnel fire-safety design
practices
NRCC-49696
Miclea, P.C.; Chow, W.K.; Shen-Wen, C.;
Junmei, L.; Kashef, A.; Kang, K.
A version of this document is published in / Une version de ce document se trouve dans:
ASHRAE Journal, v. 49, no. 8, August 2007, pp. 50-60
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INTERNATIONAL TUNNEL SAFETY DESIGN PRACTICES
Paul C. Miclea, PE, Earth Tech, USA, Prof. W.K. Chow, The Hong Kong Polytechnic University, Hong
Kong, China, Chien Shen-Wen, Central Police University, Taiwan, China, Junmei Li, Beijing
University of Technology, Beijing, China, Ahmed Kashef, PhD, National Research Centre, Canada, Kai
Kang, PhD, PE, Hatch Mott MacDonald, USA
Introduction
The catastrophic consequences of the tunnel fires (e.g., the Mont Blanc tunnel, 1999, the Austrian Kaprun
funicular tunnel, 2000, and the Swiss St. Gotthard tunnel, 2001) not only resulted in loss of life, severe
property damages, but also left the public with a lack of confidence in using such systems. Fire safety in
rail and road tunnels is challenging because of the specific features of the tunnel environment. The
sustainability of existing tunnels, given the increased road traffic and changed vehicle mix, or the new
rolling stocks, needs innovative design practices. For example, reliable and early fire detection in tunnels
can provide the tunnel operator with early warnings of fire and its location, allowing for timely activation
of the emergency response such as the emergency ventilation system.
International collaborations have been working to develop and harmonize design guidelines, such as the
Permanent International Association of Road Congresses (PIARC) and the International Union of
Railways (UIC). It’s impossible to address all tunnel fire-safety issues in an article. Instead, a number of
selected topics, such as international design practices are discussed here.
Design Practices and Examples
North America
In the United States, several government agencies and associations provide regulations and guidance for
tunnel integrity and safety. The Department of Transportation (DOT) includes specialized agencies
providing guidance for tunnel design and operation. The Federal Transit Administration (FTA) in
collaboration with the Volpe National Transportation Systems Center, the Transit Cooperative Research
Program of the Transportation Research Board, and American Public Transportation Association (APTA)
issued a document titled “Transit Security Design Considerations,” addressing the high-risk security
demands for the transit systems, particularly for tunnels and stations.
Tunnel ventilation technology evolved concurrently with the development of a dedicated computer
program in the 1970s, as part of the U.S. Department of Transportation’s Subway Environmental
Research Project. The Federal Highway Administration (FHWA) provides expertise, resources and infor-
mation on the nation’s 4 million miles of highways and roads, including many tunnels. FHWA develops
regulations, policies and guidelines, and provides federal funds to finance projects and techniques of
national interest. It is an active participant in PIARC activities, sponsor of national research projects and
cosponsor of international research programs.
ASHRAE. Rail and road tunnels, underground stations, parking garages, tollbooths, bus garages and
terminals, locomotives maintenance and repair areas are all grouped in the category of enclosed vehicular
facilities (EVF). ASHRAE and its predecessors have dealt with this group of facilities for many years,
pioneering research and standards for better, sustainable design of a safe environment (see ASHRAE and
NFPA Resources sidebar).
National Fire Protection Association (NFPA). In 1972, a tentative standard for limited access
highways, tunnels, bridges and elevated structures, was adopted by the National Fire Protection
Association. The NFPA 502 standard1 evolved and the current edition includes new requirements for the
protection of tunnel structures, emergency lighting, updates on the vehicle tunnel fire data, and
clarification of the travel distance to emergency exits. In 1975, the Fixed Guideway Transit Systems
Committee was created within the NFPA and began work on the development of a set of
recommendations applicable to most guided transit systems2 (see ASHRAE and NFPA Resources sidebar).
An important factor in advancing the design methodology for tunnel ventilation was the tremendous
progress in computer technology applicable to tunnel safety. Faster and more affordable computers
allowed a wide use of applicable computer programs, such as Subway Environment Simulation (SES) and
computational fluid dynamics (CFD),3 to provide quick and inexpensive answers to complicated network
models for airflow and smoke control.
The concept of smoke management4 was developed as a solution to the smoke migration problem, and
various specific methods have been proposed. The objectives of a smoke management system are to
reduce deaths and injuries from smoke, reduce property loss from smoke damage, and aid firefighting. A
modern smoke management system should be designed to provide a safe escape route, a safe refuge area,
or both. Current safety standards provide guidance for the implementation systems using pressure
differentials to accomplish one or more of the following:
⇒ Maintain a tenable environment in the means of egress during evacuation;
⇒ Control and reduce the migration of smoke from the fi re area;
⇒ Provide conditions outside the fire zone that assist emergency response personnel in conducting
search and rescue operations, and locating and controlling the fi re; and
⇒ Contribute to the protection of life and reduction of property loss.
The natural driving forces of smoke movement are the stack effect, wind-induced action, and buoyancy of
smoke. Action of these forces on the facility can produce significant pressure differences between
different parts inside the facility preventing smoke movement from places with higher pressure to places
with lower pressure.
North American Examples
The existing U.S. infrastructure includes some 400 highway tunnels in 35 states and thousands of
kilometers/miles of transit tunnels. The tunnels for the transit systems in New York and Boston were
constructed at the beginning of the 20th century, followed by Chicago in the 1930s and 1940s; Toronto in
the 1950s; BART San Francisco-Oakland in the 1960s; Atlanta, Baltimore, and Washington in the 1970s
and 1980s; and Los Angeles and Dallas in the 1990s, etc.
The construction of the Interstate Highway System was at its peak in the 1960s and 1970s, when several
of the existing road tunnels were built. The largest network of road tunnels was built in the 1990s, as part
of the Central Artery Project in Boston. By comparison with other countries in Europe and Asia, U.S. has
a relatively small number of road tunnels.5 Two new manuals for the tunnel management system have
been produced jointly by the FHWA and the FTA, including a software program to collect data on tunnel
components.
The subway system in Boston, built just before the end of the 19th century is the oldest in North America.
More than 100-years-old, the New York City subway system consists of more than 1,000 km of revenue
line and 468 stations, with approximately 60% underground. The weekday daily ridership on this system
exceeds 4.8 million passengers.
The Toronto subway system in Canada is an older extended underground system with a ridership in
excess of 1.1 million trips per weekday. Its emergency fire ventilation system is being upgraded to
comply with the current safety standards.
The subway of Montreal was inaugurated in 1966 and now contains 65 stations distributed out of four
lines. The construction of an extension subway towards Laval was recently completed.
The new extension adds a course of 5.2 km (3.2 miles) and three new stations: Cartier, Concorde and
Montmorency. The project also includes the construction of eight auxiliary structures. The cost of the
extension is estimated to be $803.6 million ($154.5 million per kilometer [$249 million per mile]).
The recent and new transit projects under construction or advanced design in Los Angeles, San Francisco
(airport extension) and San Jose (Silicon Valley Corridor), Seattle, and others running through tunnels are
equipped with modern ventilation systems capable of maintaining acceptable environment conditions in
stations and controlling smoke and heat in case of a major fi re underground.
New road tunnels that have been built (almost four miles in Boston, Wolf Creek Pass in Colorado), are
under construction (Devil’s Slide in California, PR Route 53) or under design (Kicking Horse in British
Columbia, Canada, 4th Bore Caldecott and Coronado in Calif., LBJ Corridor in Dallas, Pine Mountain and
Drumanard Louisville in Kentucky, SR 71 in Wisconsin, 3rd Harbor Crossing and Elizabeth River in
Virginia, Port of Miami, and so on) will have modern ventilation systems to control the emissions and
provide for smoke control and safe evacuation routes in case of tunnel fires. Some of the existing tunnels
have been or are being retrofitted and provided with upgraded ventilation systems (I-90 and Mt. Baker
Ridge in Seattle, Eisenhower in Colorado, Detroit-Windsor, Wilson in Hawaii).
Europe
From 2000 to 2001, the United Nations (UN) Economic Com-
mission for Europe (ECE) formed an ad hoc multidisciplinary
Group of Experts and developed recommendations on road
tunnel safety under four categories of road users, operations,
infrastructure and vehicles.6 In April 2004, the European Com-
mission approved Directive 2004/54/EC on minimum safety
requirements for tunnels in the Trans-European road network.7
This is to ensure a uniform and high level of safety by
prevention of incidents and reduction of their consequences.
The directive applies to both new and existing tunnels more
than 500 m long, and mandates 10 to 15 years for each
member state to bring its tunnels in compliance.
Classification of tunnels is developed based on tunnel length
and traffic volume for each of which a minimum safety
requirement is established for all aspects of fire safety, such as
the emergency exit sign arrangement, which also is being
considered in the next revision of NFPA 502. The Directive
calls for regular information campaigns on road user behavior,
especially in such situations as vehicle breakdown, congestion,
accidents and fires. Safe driving in tunnels under these
circumstances has been developed as an official EU
document.8 The directive has included specific requirements
on tunnel ventilation, some of which are:
⇒ Mechanical ventilation is required for all tunnels
longer than 1 km (0.6 miles) with an annual average daily traffic volume higher than 2,000
vehicles per lane;
ASHRAE & NFPA Resources
Chapter 13 of 2007 ASHRAE Handbook—
HVAC Applications, covers ventilation
requirements for normal climate control and
emergency situations in EVF, as well as
design approaches for mechanical ventilation
for various emergency scenarios.
ASHRAE Technical Committee 5.09,
Enclosed Vehicular Facilities, has members
from various U.S. and international
organizations and administrations equally
representing train and bus operators, university
professors, researchers, consultants and
designers, equipment manufacturers and
suppliers, government bodies, etc.
ASHRAE Technical Committee 5.06, Control
of Fire and Smoke, and Handbook Chapter 52,
Fire and Smoke Management, are dedicated to
fire protection and smoke-control systems,
providing useful information applicable to
EVF as well.
The first edition of NFPA 130, Standard for
Fixed Guideway Transit Systems, including
fire protection requirements, was adopted by
NFPA in 1983. The newest version was
published in 2006.2
⇒ Transverse or semitransverse ventilation is required for tunnels with bidirectional traffic and
higher traffic volumes, or when tunnel length exceeds 3 km (1.9 miles);
⇒ Longitudinal ventilation only is allowed through risk analysis for bidirectional or congested
unidirectional tunnels; and
⇒ New tunnels should not be designed with a longitudinal gradient more than 5% unless
geographically impossible. Risk analysis is needed for gradients higher than 3%.
Transverse and semitransverse ventilation is advantageous as
the smoke extraction can be used to limit the smoke spread in
the tunnel (Figure 1). Using controllable smoke exhaust
dampers and a steering process to adjust the longitudinal air
velocity is mandatory for bidirectional tunnels with a traffic
volume higher than 2,000 vehicles per lane and a tunnel length
more than 3 km (1.9 miles). A semitransverse ventilation system
is installed in Mont Blanc tunnel, whereas St. Gotthard tunnel
has full transverse ventilation. A report on “System and
Equipment for Fire and Smoke Control in Tunnels” addresses
various types and installations of tunnel ventilation systems, (it
will be published in 2007 by PIARC).
Figure 1: Tunnel cross-sections.8
For tunnel ventilation design, the UN ECE recommendations
suggested a minimum fire size of 30 MW (102 MBtu/h). This is
used in many countries such as Austria, Germany and Swit-
zerland, whereas provisions of 50 MW (170 MBtu/h) can be
found in the design standards of Germany and Britain. However,
a much higher fire heat release rate could develop, as
demonstrated in the Runehamar tunnel tests, where fi re from
ordinary heavy goods vehicles could reach as high as 200 MW
(680 MBtu/h).9 A comprehensive and systematic
implementation of the safety measures including ventilation,
egress, rescue and training is necessary.
European Examples
Europe has some of the world’s longest road tunnels, in operation and under construction: Laerdal Tunnel
in Norway, completed in 2000 is 24.5 km long (15.3 miles); St. Gotthard in Switzerland is 16.9 km (10.5
miles); Frejus between France and Italy 12.9 km (8 miles). The new Rogfast subsea tunnel in Norway will
be 24.2 km (15 miles) and the A86 West Tunnel on the ring road around greater Paris, currently under
construction, includes an innovative 10 km (6.2 miles) double deck for light vehicles and a separate 7.5
km (4.7 miles) single deck for all traffic, including heavy goods vehicles. After the completion in 1994 of
the 50.5 km (31.4 miles) Channel Tunnel between France and England; 34.6 km
(21.5 miles) Loetschberg in Switzerland; and 28.4 km (17.6 miles) in Spain, even longer rail tunnels are
under construction; such as the Gotthard Base at 57.1 km (35.5 miles), which will be followed by another
one in Stage 2 (2015–2020) of 75 km (46.6 miles).
The London Underground, one of the oldest in the world, has more than 400 km (248 miles) of line, 274
stations and up to 2.7 million passenger trips per weekday.
Another old subway, built in the late 1890s, is in Budapest. Many other systems are in Western Europe
(Paris, Lille, Lyon, Madrid, Lisbon, Berlin, Frankfurt, Rome, Milan, etc.) and are continually expanding.
Also, there are many subway systems in Russia and Eastern Europe, but it would be difficult to describe
all of them in an article. Moscow’s “Metropoliten” has the highest ridership in the world (up to 9 million
passengers a day).
Asia/Far East
In Hong Kong, the fi re-safety strategies10 optimize fire protection and fire prevention measures to attain
specified fire-safety objectives.
Three main fi re-safety goals11 should be clearly defined to develop these fire-safety objectives: life safety;
property and building protection; and minimum disturbance to normal operation of business. All these
goals are important for designing fire safety for the new railway lines and for upgrading provisions of the
existing lines. The goals also should be supported by specific fire-safety objectives.
Fire engineering systems should be specified12 clearly and include at least three parts: detection and alarm
system; fire control system; and air and smoke control system. Other auxiliary systems include emergency
lighting, exit signs, essential power supplies and others. Fire suppression system such as the automatic
sprinkler systems could be used to control a fire, pre-wet the areas and cool the air temperature before the
freighters entered the stations. However, the hot steam generated might hurt the occupants, including the
passengers, staff and freighters. Therefore, the operation time of the fire suppression system should be
watched.
Keeping the thermal and toxic effects to acceptable and tenable limits are extremely important for
evacuation. Tenability limits commonly considered in Hong Kong13 are:
⇒ Radiative heat flux: 2.5 kWm–2;
⇒ Carbon monoxide concentration: 6,000 to 8,000 ppm for five minutes exposure;
⇒ Smoke layer temperature: 120°C (248°F); and
⇒ Smoke layer interface height: 2.5 m (8 ft).
For railway transit systems in Hong Kong, the proposed “total fire-safety concept”14 must include, as a
minimum, provisions to ensure that all the hardware fire-safety provisions on passive design and active
fire protection systems work and people know what to do in a fire. There must be well-planned software
for fire-safety management.
In Beijing, ventilation and smoke exhaust systems were designed based mainly on Metro Design Code,
GB-50517-2003.15 Smoke compartmentalization is set at the platform and lobby level, and each area is
not to exceed 750 m2 (8,100 ft2). The smoke exhaust rate is estimated at 1 m3/min (35 ft3/min) for 1 m2
(10.8 ft2) floor space, downward air velocity over 1.5 ms–1 (4.9 fts–1) in the staircase or escalator exits
accessible to the platform. When a fire occurs in the tunnel, the required smoke exhaust rate is determined
to achieve a cross-sectional velocity in the tunnel more than 2 ms–1 (6.5 fts–1), but less than 11 ms–1 (36
fts–1). As stated earlier, performance-based design also is accepted for the old system upgrades, as well as
for the new lines or system design.
In Taipei, smoke control systems in subway stations were implemented in four timeframes:
Before 1996. Consultants were appointed and NFPA 130 was referred to while designing the tunnel
ventilation fans (TVF) and the under platform exhaust (UPE) systems. Air is drawn from the ambient and
exhausted at the platform floor level with a downstream velocity of more than 2.5 ms–1 (8.2 fts–1).
1996 – 2003. A fire prevention and fire service installations code was established, with a more vigorous
assessment on the smoke control design. Consultants had to follow NFPA 130 and the associated fire
regulations in Taiwan. Simulation results of the fire environment and evacuation procedures were
justified.16 Hot smoke tests were required for all stations with design fire size from 2 to 25 MW (6.8 to 85
MBtu/h). The effect of smoke movement on evacuation was observed. The assessment and inspection
procedures took over one year.
2004. New fire codes were introduced by the Building Authority, with a mandatory inspection by the
China Building Centre, a non-profit organization. CFD began to be widely used. Now, the Fire Dynamics
Simulator (FDS)17 is used in almost all projects. Inspections of smoke control systems became more
complicated by including the following key points:
⇒ Smoke control and evacuation studies on the same space and fi re scenarios;
⇒ The worst scenario identification or;
⇒ Clarification of all simulation details;
⇒ Inclusion of visibility and thermal radiation;
⇒ Requirement of on site hot smoke test; and
⇒ Submission of an all emergency plan.
2006. The fire-safety code for subway stations and railway tunnels was implemented by the Highway and
Traffic Department. The smoke control in all subway systems should follow NFPA 130 and CFD should
be used when necessary. The code is no more prescriptive, but performance-based or scenario-based.
Asia/Far East Examples
Asia has some of the longest tunnels, for rail and road. In Japan, the Seikan tunnel is 53.9 km (33.5 miles)
long; Hakkoda is 26.5 km (16.4 miles); Iwate 25.8 km (16 miles); and Kanetsu road tunnel is
11.1 km (6.9 miles). Long tunnels exist in China (Wushaoling rail at 21.1 km [13.1 miles], Zhongnanshan
road at 18 km [11.2 miles]) and Taiwan (Hsuehshan road tunnel of 12.9 km/8 miles).
In Hong Kong passenger railway and subway systems are operated by two organizations that are
proposed to be merged soon. The existing systems are East Rail, Kwun Tong Line, Tsuen Wan Line,
Island Line, Tung Chung Line, Airport Express Line, Tseung Kwan O Line, West Rail, Ma On Shan Rail
and Disneyland Resort Line. Fire-safety strategies were planned carefully in new stations and there are
plans for upgrading the old stations for fire life safety.
Beijing has four subway lines at the moment, but eight will be in operation by 2008. Lines 1 and 2 are
being operated since the 1960s, with a passenger loading of more than 1.3 million per day. Smoke exhaust
and emergency ventilation systems are provided for underground stations and tunnels. Due to space
limitations, the normal ventilation and air-conditioning systems are integrated with the smoke control
system. Normal ventilation mode can be shifted to emergency mode immediately once a fire is detected.
For the first two lines, the fire-safety provisions were designed based on old fire codes. There is an action
plan to upgrade the fire-safety provisions with three main tasks: upgrading ventilation and smoke exhaust
systems, installing fi re suppression, water piping systems, automatic fi re detection and alarm systems.
Research
In the 1990s a major research program was carried on in an abandoned tunnel in West Virginia. The
Memorial Tunnel Fire Ventilation Test Program (MTFVTP) was cosponsored by the Massachusetts
Turnpike Authority, FHWA and ASHRAE for the Central Artery Project in Boston and included 98
controlled fire tests of up to 100 MW (680 MBtu/h), leading to valuable technical information and
enhancements of tunnel ventilation engineering and applicable software.
An unprecedented number of research projects were launched in Europe in the last decade, in response to
several tragic fi re accidents in tunnels. These projects (Table 2) constitute a comprehensive assessment of
tunnel fire safety. For example, the FIT thematic network serves as data gathering, DARTS explores
technologies for new tunnel constructions and UPTUN develops innovative and sustainable technologies
for existing tunnels, whereas the Safe-T thematic network aims at harmonization of a global approach to
tunnel safety. Although most of the projects focus on road tunnels, they also include metro and rail
tunnels, such as FIT, Safe-T and UPTUN. However, fire safety in rail tunnels can be improved through
regulations for the rolling stock and operational procedures.3 This is in contrast to road tunnels, in which
road users, traffic and vehicle variations must be considered.6
Lessons Learned and What’s Next
The lessons learned from recent tunnel fire tragedies require attention and implementation of credible and
economically feasible recommendations such as the following:
⇒ The emergency ventilation system must be capable of handling combinations of worst-case fire
conditions: fi re size, location, fan availability, second train nearby, etc.
⇒ Vehicles are the main causes of fire, due to technical or mechanical faults or due to people’s
negligence or malicious intentions (such as arson).
⇒ Simultaneous/coincidental occurrence of other factors that contribute to the worst-case conditions
should be considered including: · Activating the emergency ventilation system as soon as
⇒ possible after the fire is detected and its location is confirmed, and applying the preestablished
scenario measures; and · Ensuring fans are never reversed once activated in one direction.
⇒ Further investigational work is needed and the fi re-safety objectives3,18 for public transport must
be reviewed carefully. Total fi re safety14 can be used to provide passive fi re protection, active
fire system and fi re-safety management. The following are suggested to be considered in further
in-depth investigations.
⇒ A fire in the train and a fire in the railway terminal are not the same. In the train, the thermal
response of the train system to an ignition source should be evaluated.
⇒ Materials with fire retardants should be tested under high radiative heat fluxes in a cone
calorimeter and supported by full-scale burning tests. Attention should be paid to smoke toxicity
of materials. The materials used should be controlled by proper assessment tests.
⇒ New active fire protection systems and extinguishing concepts are needed.
⇒ During a tunnel fire, crowd movement and control tend to be poor. The presence of platform
screen doors might affect evacuation away from the train.
⇒ The following fi re-safety related issues must be considered in the analysis:
o Luggage and baggage (especially tourist groups traveling to the airport),
o Fire retardants to be tested under high heat flux with full-scale burning tests,
o New technology on active protection systems · Improved fire-safety management
(including crowd movement and control),
o Total fi re-safety concept,
o Smoke toxicity of materials and its control.
References
1. NFPA 502, Standards for Road Tunnels, Bridges, and Other Limited Access Highways. 2004.
National Fire Protection Association (NFPA).
2. NFPA 130, Standard for Fixed Guideway Transit and Passenger Rail System. 2007. National
Fire Protection Association.
3. 2007 ASHRAE Handbook—HVAC Applications, Chapter 13, “Enclosed Vehicular Facilities.”
4. Klote, J. and J. Milke. 1992. Design of Smoke Management Systems. Atlanta: ASHRAE.
5. Botelho, F.V. 2005. “A Light at the End of the Tunnel.” Federal Highway Administration.
www.fhwa.dot.gov/infrastructure/ asstmgmt/tunnel.htm.
6. Recommendations of the Group of Experts on Safety in Road Tunnels, Inland Transport
Committee, Economic Commission for Europe, Economic and Social Council of United Nations,
TRAN/AC.7/9 (2001).
7. Directive 2004/54/EC of the European Parliament and of the Council on Minimum Safety
Requirements for Tunnels in the Trans-European Road Network, April 2004, Brussels, Belgium.
8. U.S. DOT Federal Highway Administration, Office of International Programs. 2006.
“Underground Transportation Systems in Europe: Safety, Operations, and Emergency Response.”
FHWA-PL-06-016.
9. Ingason, H., A. Lönnermark, 2005. “Heat release rate from heavy goods vehicle trailer fires in
tunnels.” Fire Safety Journal, 40:646–668.
10. British Standards Institution. 2001. “BS 7974, Application of Fire Safety Engineering Principles
to the Design of Buildings–Code of Practice.”
11. Chow, W.K., M.Y. Ng. 2003. “Review on fire safety objectives and application for airport
terminals.” ASCE Journal of Architectural Engineering 9(2):47–54.
12. Buildings Department, Hong Kong. 1996. Code of Practice for the Provision of Means of Escape
in Case of Fire.
13. Chow, W.K., et al. 2006. “Case study for performance-based design in Hong Kong.” Project
presented at the 6th International Conference on Performance-Based Codes and Fire Safety
Design Methods.
14. Chow W.K. 2004. Proceedings of the Fire Conference 2004–Total Fire Safety Concept.
15. 2003. GB 50517-2003, Metro Design Code. Beijing: Chinese Planning Publishing House.
16. Chen, F. 2003. “Smoke control of fires in subway stations” theoretical and computational fl uid
dynamics.” Theoretical and Computational Fluid Dynamics 16:349–368.
17. National Institute of Standards and Technology. 2006. Fire Dynamics Simulator (Version
4.0.7)—User’s Guide, Fire Research Division, Building and Fire Research Laboratory, National
Institute of Standards and Technology.
18. NFPA. 2000. NFPA 92A, Recommended Practice for Smoke-Control Systems.
Safety & Security in Tunnels
Underground infrastructures are considered high-order
terrorist targets because of their high visibility and cost.
They have been the target of 40% of all terrorist acts
worldwide. The type of threats can range from a fire
incident (vehicle fuel, flammable cargo, liquid fuel
tankers, flammable gas tankers), explosions (car bombs,
truck bombs, boiling liquid expanding vapor explosion,
emplaced charges), radioactive, chemical, to a
biological attack. The damage can be somehow limited
(casualties, vehicle damage, cosmetic, damage to
ventilation and lighting systems, traffic sensors, etc.)
and structurally major (liner, roadway, ceiling collapse,
portal structural damage, tunnel flooding for submerged
tunnels, complete tunnel collapse). Resulting repair
costs can be in the range of thousands to hundreds of
millions of dollars and the down time can be a couple
days to more than a year. Such costs often can be
dwarfed by the costs associated with business disruption
from these incidences, which often can be much greater
than the physical repair costs.
Over the past 10 years, terrorist attacks on transportation
systems have claimed many lives and caused major
disruption. Events such as those on the Tokyo subway
(1995: 12 deaths and thousands sick), on the train
station in Madrid (2004 and 2005: 191 deaths), on the
Moscow Metro (2004: 39 deaths) and London (2005: 56
deaths) resulted in raised awareness of the vulnerability
of infrastructural systems to terrorists’ attacks. They
have raised many questions with regards to the
management of safety and security issues of existing
and projected infrastructure in enclosed spaces, which
require consideration and solutions.
Given the current gaps in technical knowledge and the
complexity of such transportation systems, a new effort
in research to improve safety and security in these
systems is vital. The need for technical improvements,
as well as consideration of various human factors, has
already been recognized worldwide. The U.S. Federal
Highway Administration (FHWA) has released a report,
developed by the Office of Infrastructure Research and
Development (R&D), proposing a plan to support
national disaster preparedness and response and
recovery efforts, as well as to initiate and facilitate
research and technology development in support of a
more secure highway bridge and tunnel system. Other
offices of the FHWA are addressing research and
development associated with securing other parts of the
national highway system. Agencies and organizations
like FHWA, American Association of State Highway
and Transportation Officials (AASHTO), and the
Intelligent Transportation Society of America (ITS
America) have developed several publications. In an
effort to strengthen transportation security, several long-
term challenges have been identified. These include
developing a comprehensive risk management
approach; establishing effective coordination among the
many responsible public and private entities; ensuring
adequate workforce competence and staffing levels; and
implementing security standards for transportation
facilities, workers, and security equipment. In the
description of the seventh framework program of the
European Community (EC), “safety and security” is
explicitly addressed as an individual topic for R&D
activities and a first “European Conference on Security
Research” was held in February 2006. Moreover, the
EC strategic initiative on safety and security in
underground and enclosed spaces includes several
research projects. The L-surF (large scale underground
research facility) project uses large-scale R&D, testing,
training and education as tools to improve the safety and
security of underground and enclosed spaces. The
UPTUN project aims at developing innovative
technologies in the areas of detecting, monitoring,
mitigating measures, and protecting against structural
damage. It also aims at developing risk-based evaluation
and the upgrading of models.
It is not possible to protect everything against
everything. Therefore, choices must be made in a
logical manner as to which
facilities/personnel/paraphernalia (critical assets) need
most protection and what measures should be taken to
protect them.
To decide as to which objects should be protected, a
vulnerability assessment (risk analysis identifies the
probability and consequences of an undesirable event)
should be conducted on all national assets. A
vulnerability assessment identifies weaknesses that may
be exploited by identified threats and suggests options to
address those weaknesses. The more vulnerable an
object is, the higher the probability of attack.
In general, five basic categories characterize the
protective countermeasures systems: deterrence,
detection, defense, defeat, and strengthening of assets
by structural hardening. The countermeasures
commonly take the form of site work (associated with
everything beyond 1.5 m (5 ft) from an asset and can
include perimeter barriers, landforms, and standoff
distances), building (measures directly associated with
buildings including walls, doors, windows, and roofs),
detection (elements detect such things as intruders,
weapons, or explosives including intrusion detection
systems (IDS), closed-circuit television (CCTV)
systems, guards, etc.), and procedural elements
(protective measures required by state or local security
operation plans to provide the foundation for developing
the other three elements).
