Recommendations for Bridge and Tunnel Security 

Requested by: The American Association of State Highway 

and Transportation Officials (AASHTO) 

Transportation Security Task Force 

Prepared by: The Blue Ribbon Panel on Bridge and 

Tunnel Security 

SEPTEMBER 2003
 

Recommendations for Bridge and Tunnel Security
 

Requested by:	 The American Association of State Highway 

and Transportation Officials (AASHTO) 

Transportation Security Task Force 

Prepared by:	 The Blue Ribbon Panel on Bridge and
 

Tunnel Security
 

SEPTEMBER 2003
 
Acknowledgments 

This report was requested by the American Association of State Highway and 

Transportation Officials (AASHTO) Transportation Security Task Force and the Federal 

Highway Administration (FHWA). The work was authored by the Blue Ribbon Panel on 

Bridge and Tunnel Security, which included James E. Roberts, P.E. (Chair), Dr. John M. Kulicki, 

P.E. (Vice Chair), Dwight A. Beranek, Joseph M. Englot, Dr. John W. Fisher, P.E., Henry 

Hungerbeeler, Dr. Jeremy Isenberg, Dr. Frieder Seible, Kenneth Stinson, Dr. Man Chung Tang, 

and Kary Witt. Sponsor liaisons included James D. Cooper, P.E., and Steven L. Ernst, P.E., 

representing FHWA, and Dr. Anthony R. Kane, Paul V. Liles, Jr., P.E., and Mary Lou Ralls, P.E., 

representing AASHTO. Science Applications International Corporation provided technical 

support to the Blue Ribbon Panel on Bridge and Tunnel Security under a contract with the 

National Cooperative Highway Research Program (NCHRP). 

Foreword 

A note from the American Association of State Highway and Transportation Officials and the 

Federal Highway Administration: 

The Blue Ribbon Panel on Bridge and Tunnel Security was formed from renowned engineering experts who generously contributed their time, without compensation, to guide 

government leaders, infrastructure owners, and the engineering community on how to 

improve the security of bridges and tunnels. Infrastructure owners are faced with new and 

largely unexpected challenges to provide physical security against terrorists’ attacks on 

their critical structures. The panel’s initiative and collective wisdom reflected in this report 

will help America meet these challenges. 

DISCLAIMER 

The opinions and conclusions expressed or implied are those of the Blue Ribbon Panel on Bridge 

and Tunnel Security and are not necessarily those of FHWA or AASHTO. 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Table of Contents 

Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
 

1. Background, Panel Membership, and Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
 

2. Blue Ribbon Panel Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
 

2.1 Overall Strategy for Bridge and Tunnel Security — “The Bigger Picture” . . . . . . . 9
 

2.2 Framework for Planning, Design, and Engineering . . . . . . . . . . . . . . . . . . . . . . . . 10
 

2.3 Prioritization and Risk Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
 

2.4 Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
 

2.5 Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 

2.6 Countermeasures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
 

2.7 Codes and Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
 

3. Overarching Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 

3.1 Institutional Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 

3.2 Fiscal Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
 

3.3 Technical Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
 

4. Policy Foundations And Institutional Continuity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
 

4.1 Foundations for Policy and Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
 

4.2 Institutional Continuity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
 

5. Planning, Design, and Engineering Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . 19
 

5.1 Review and Prioritization Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
 

5.2 Research and Development. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
 

5.3 Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
 

5.4 Technology Development And Dissemination . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
 

6. Recommendations Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
 

6.1 Short-term Strategies for Improving Bridge and Tunnel Security . . . . . . . . . . . . . 29
 

6.2 Mid-term Strategies for Improving Bridge and Tunnel Security . . . . . . . . . . . . . . 31
 

6.3 Long-term Strategies for Improving Bridge and Tunnel Security . . . . . . . . . . . . . 31
 

6.4 Design Criteria/Guidance to Highway Infrastructure Owners/Operators . . . . . . 32
 

6.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
 

Appendix A: Countermeasure Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
 

Appendix B: Operational Security Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
 

Appendix C: Case Study in Bridge and Tunnel Risk Assessment . . . . . . . . . . . . . . . . . . . . 43
 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Executive Summary 

Terrorism against American citizens and assets is real and growing.1 The number and intensity of domestic and international terrorist events, along with the September 11, 2001, 

attacks, change the way Americans think and live. Terrorists attack targets where human 

casualties and economic consequences are likely to be substantial. Transportation and related assets are attractive terrorist targets because of their accessibility and potential impact 

on human lives and economic activity.2 Al Qaeda and other terrorist groups are perceived 

to be unyielding, tenacious, and patient. An Al Qaeda terrorist training manual captured in 

England contains goals that included missions for “gathering information about the The highway 

infrastructure has 

vulnerabilities, 

which must be 

addressed. 

This is important
 

enough to be a 

matter of national 

security policy. 

Improvements in 

homeland security 

must address 

improvements to 

critical bridges 

and tunnels. 

f 

enemy and blasting and destroying bridges leading into and out of cities.”3 In a similar vein, as a Caltrans-funded Bay Area Security Enhancement Project neared completion, a captured Al-Qaeda leader revealed “a bridge in San Francisco or San 

Mateo was on a list of possible targets for the terrorist network.”4 

A Blue Ribbon Panel (BRP) of bridge and tunnel experts from professional practice,
 

academia, federal and state agencies, and toll authorities convened to examine bridge 

and tunnel security and to develop strategies and practices for deterring, disrupting,
 

and mitigating potential attacks. The BRP, sponsored jointly by the Federal Highway 

Administration (FHWA) and the American Association of State Highway and 

Transportation Officials (AASHTO), acknowledges that the nation’s bridges and tunnels 

are vulnerable to terrorist attacks. The intent of this paper is to recommend policies 

and actions to reduce the probability of catastrophic structural damage that could 

result in substantial human casualties, economic losses, and socio-political damage. 

number of parallel routes, can lead to the conclusion that the transportation system 

is so robust that it is not susceptible to significant disruption by terrorist attack. In 

the opinion of the BRP members, this conclusion is incorrect. In many parts of the 

country, the transportation system is straining to keep up with the current demands o

society and the economy. The actions of terrorists can impose critical damage to some 

bridges, and, with explosive forces, exert loads that exceed those for which components 

are currently being designed. Worse yet, in some cases, the loads can be in the opposite 

direction of the conventional design loads. 

The success and safety of the transportation system, combined with the perceived 

1 A report compiled by the Transactional Records Access Clearinghouse (TRAC) from the Federal Bureau of Investigation (FBI) budget
 

reports, budget submissions, and Congressional Research Service reports shows FBI terrorism investigations growing by nearly 5 percent between fiscal year (FY) 1997 and FY 2000 and anti-terrorism funding growing by 25 percent between FY 2000 and FY 2002.
 

These increases are a direct reflection of both growth in and concerns about domestic and international terrorism. TRAC is a data
 

gathering, data research, and data distribution organization associated with Syracuse University. See http://trac.syr.edu/ for more
 

information.
 

2 Dan Hartman,TSA, briefed the BRP on January 27, 2003, in San Francisco and noted the following with respect to transportation system vulnerabilities: (1) highways, bridges, tunnels, trains, and subways are readily accessible; (2) most fixed transportation infrastructure lies unguarded; (3) transportation infrastructure presents prime opportunities for terrorist attacks; and (4) a small, directed force
 

can inflict serious injury, tremendous damage.
 

3 Texas DOT Project No. 0-4569, Phase 1 (Literature Review and Work Plan), Executive Summary, August 15, 2002. 

4 “Anti-Terrorist Security Network Almost Done on Bay Area Bridges and Tunnels,” The San Jose Mercury News, March 25, 2003. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

The nation’s highway system has vulnerabilities, which must be addressed. 

This is important enough to be a matter of national security policy. 

Among the 600,000 bridges in the United States, preliminary studies indicate that there are 

approximately 1,000 where substantial casualties, economic disruption, and other societal 

ramifications would result from isolated attacks.5 Additionally, the U.S. transportation system includes 337 highway tunnels and 211 transit tunnels; many are located beneath bodies 

of water, and many have limited alternative routes due to geographic constraints.6 The BRP 

recommends prioritization of these bridge and tunnel assets, followed by risk assessment as 

a guide for allocating federal and state funds to address security concerns, and then implementation of cost-effective operational security measures and engineering design standards 

to reduce the vulnerability of high priority bridges and tunnels to terrorist attacks. 

After considering the nature of the bridge and tunnel components of the highway system 

and lessons learned from natural disasters, the effects of transportation-related consequences of the September 11th attack, and the recent barge collision in Oklahoma, the 

panel has determined that loss of a critical bridge or tunnel at one of the numerous “choke 

points” in the highway system could result in hundreds or thousands of casualties, billions 

of dollars worth of direct reconstruction costs, and even greater socioeconomic costs. 

Improvements in homeland security must address improvements to 

critical bridges and tunnels. 

In the judgment of the BRP, the ordinary cost of construction to replace a major long-span 

bridge or tunnel on a busy interstate highway corridor in the United States may be $1.75 billion. Experience in reconstruction following major earthquakes suggests that expediting 

replacement can double the cost of construction. Program costs may double this figure again. 

The hundreds of fatalities that may occur, possible environmental consequences, and the fact 

that the site would be a crime scene under investigation, further compound recovery and 

replacement. During the five years estimated for reconstruction, the socioeconomic loss to the 

region resulting from losing as many as 14 Interstate highway lanes for an extended period is 

many times the replacement cost of the facility. Finally, revenue from toll facilities lost through 

a terrorist attack might dramatically affect the viability of an agency or toll authority. 

Although past attempts at quantifying the total cost of a bridge or tunnel outage from natural disasters have not yielded widely accepted results, the BRP believes that loss of a critical 

bridge or tunnel could exceed $10 billion. A concerted attack on two or more facilities 

would result in a synergy where the total cost would be more than the sum of individual costs, 

5	 The estimate of 1,000 critical bridges is based on information presented in National Needs Assessment for Ensuring Transportation, 

Infrastructure Security: Preliminary Estimate, NCHRP Project 20-59(5), prepared by Parsons Brinckerhoff and SAIC, June 2002. 

6	 Development of a Tunnel Management System – Phase I Report, prepared by Gannett Fleming for the Federal Highway Administration 

and the Federal Transit Administration under contract # DTFH61-01-C-00067, March 2003. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

especially when regional socioeconomic consequences are considered.7 Moreover, the regional 

economic consequences of a major coordinated terrorist attack on multiple facilities are almost 

inestimable. The September 11, 2001, attacks on the World Trade Centers resulted in significant 

job losses in the area: 

Since the high water mark of 2000, Manhattan has lost some 85,000 jobs, approximately 

28,000 of which were related to firm relocations from Manhattan and the remaining 

57,000 to recession-related cutbacks and secondary employment losses triggered by the 

disaster. At least one third of the job loss, or 30,000 jobs, were in finance and insurance, 

followed by another 20,000 in services.8 

The attacks also affected tourism: 

The events of September 11th have had a tremendous impact on the City’s visitor market. The decline in over five million visitors to 32 million in 2001 (returning to 1996­

1997 levels) can be attributed in part to the weakening economy and concerns over 

security, and in part to the loss of significant Downtown sites.9 

Eighty-five percent of the commuters in Lower Manhattan use public transit because the number of private automobiles cannot be accommodated downtown. As a result of the September 

11, 2001, attack, the PATH commuter rail line and station were rendered unusable. The line carried 67,000 passengers each weekday to Lower Manhattan and was closed for about two years. 

This was a major factor in the relocation of 103 firms, 1.1 million square feet of office space, 

and 11,700 jobs from Lower Manhattan to New Jersey. This is indicative of what the socioeconomic loss of a major transportation route can be.10 

With prospects of such losses and related replacement and user costs looming in the aftermath 

of a successful terrorist attack, the U.S. Congress recognized that terrorism presents risks 

unlike risks typically encountered by those who own and/or operate assets that are important 

to our nation’s well-being.11 Typically, asset owners manage risks associated with natural hazards 

using well developed risk assessment methods based on mature occurrence models and actuarial loss data that allow them to make informed trade-off decisions among mitigation alternatives 

and facility insurance. Unlike the case of natural hazards, we are in the dawn of an era in which 

asset owners feel overwhelmed by uncertainties about the occurrence and potential costs of 

terrorist attacks and about their legal responsibilities to protect the users of their facilities. 

7	 The White House Report, The National Strategy for the Physical Protection of Critical Infrastructures and Key Assets, February 2003, 

acknowledges the close relationship between the nation’s transportation infrastructure and other segments of the economy: 

“Interdependencies exist between transportation and nearly every other sector of the economy. Consequently, a threat to the transportation sector may impact other industries that rely on it. Threat information affecting transportation modes must be adequately 

addressed through communication and coordination among multiple parties who use or rely on these systems.” 

8	 Market Analysis for Site Plan Options – Phase One Summary Report (Draft), prepared for the Port Authority of New York and New Jersey 

and the Lower Manhattan Development Corporation by Beyer Blinder Belle and Parsons Brinckerhoff, August 28, 2002, p. 3.16. 

9	 Ibid., p. 3.19. 

10	 Ibid., multiple pages. 11	 See the preamble to PL 107-297, the Terrorism Risk Insurance Act of 2002, enacted November 26, 2002, in which the unique risks associated with acts of terrorism are acknowledged and temporary financial compensation to insured parties is proposed as a means of 

contributing to the stabilization of the U.S. economy in a time of national crisis, while the financial services industry develops the systems, mechanisms, products, and programs necessary to create a viable financial services market for private terrorism risk insurance. 

3 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

It is therefore imperative to identify critical transportation infrastructure, particularly 

bridges and tunnels, and to provide strategic guidance for investing in countermeasures and 

risk mitigation strategies. In the case of bridges and tunnels of regional or national significance, the federal government is the funding source of last resort for recovery operations 

and to restore capability in the event of terrorist attacks. Significant investment to prevent 

or reduce the consequences of such attacks may well be justified as an alternative to the 

high cost of response and recovery and subsequent socioeconomic damage. 

Overarching Recommendations 

The BRP makes the following seven overarching recommendations to accomplish the 

overall goal of reducing the vulnerability of bridges and tunnels to terrorist attacks. These 

recommendations fall into three areas: institutional, fiscal, and technical. Recommendations 

in the fiscal and institutional areas are prerequisites to effective implementation of recommendations in the technical area. These overarching recommendations are as follows: 

Institutional Recommendations 

•	 Interagency Coordination. Recognizing the importance of both operational and 

engineered solutions and the expertise that exists within the owner/operator 

community, it is vital that FHWA, AASHTO, Transportation Security Administration 

(TSA), and other highway transportation stakeholders collaborate to ensure that 

assessment methodologies and security solutions meet stakeholder needs. 

•	 Outreach and Communication Strategies. FHWA and AASHTO, in partnership with 

other organizations, should disseminate information about bridge and tunnel security and cost-effective countermeasures to decision makers, facility owners/operators, 

designers, and elected officials. 

•	 Clarification of Legal Responsibility. FHWA should seek to clarify the legal position of 

state Departments of Transportation (DOTs) and public transportation authorities 

with respect to their responsibility to act on the indications of risk studies for 

their facilities. 

Fiscal Recommendations 

New Funding Sources for Bridge/Tunnel Security. Bridge and tunnel security issues should be 

addressed with new funding provided beyond and outside of current federal-aid highway 

funding sources. 

Funding Eligibility. To address the need for flexibility to fund critical structures on a programmatic basis, Title 23, Sections 144 and 133, should be amended to allow expenditures for costeffective strategies for bridge security, as was done for seismic retrofitting. This change should 

allow federal funding for critical structures without regard to deficiency as currently defined. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Technical Recommendations 

Technical Expertise. Security solutions should be “engineered” and FHWA, as the nation’s 

primary federal agency with the necessary engineering expertise, should collaborate with 

the TSA in its effort to prioritize critical bridges and tunnels and to administer fund allocation to responsible agencies to meet high priority security needs. 

Research, Development, and Implementation. Engineering standards do not exist regarding 

security concerns for bridges and tunnels. Technology should be developed and validated 

through appropriate research and development (R&D) initiatives identified here to address 

this need. 

These seven overarching recommendations form the backbone of the BRP’s perception of 

bridge and tunnel security requirements. Although the Panel believes that the fiscal and 

institutional recommendations offered above are essential to cost-effective bridge and tunnel security enhancement, the primary focus of this report is on the technical recommendations, reflecting both the primary objective of this effort and the collective strengths and 

expertise of the panelists. These technical recommendations include methods for identifying 

critical bridges and tunnels, operational security measures that employ effective security 

procedures and available technology, engineering and design approaches for reducing the 

vulnerability of critical infrastructure, and research and development agenda to gain a 

greater understanding of structural responses to attacks and countermeasures to avoid or 

mitigate potential negative consequences. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

6 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

1. Background, Panel Membership, and Charge 

Following the September 11, 2001, attacks, bridge and highway infrastructure engineers face 

new and largely unexpected challenges relating to the physical security of critical structures 

against terrorists attacks. Although the September 11th attacks targeted buildings, threats 

against bridges and tunnels and other highway infrastructure in various parts of the United 

States have heightened awareness and concern. Bridge and highway engineers are being asked 

to assess the vulnerability of structures and to identify means for reducing this vulnerability. 

In response to this need, the American Association of State Highway and Transportation 

Officials (AASHTO) Transportation Security Task Force sponsored the preparation of a 

guide to assist transportation professionals as they identify critical highway assets and take 

action to reduce their vulnerability.12 Further, the U.S. Army Corps of Engineers (USACE) has 

long considered how to make key structures more resilient against enemy attack. Additionally, 

to develop and transfer knowledge rapidly within the bridge community to improve structure 

protection against attack, a series of workshops was conducted in early 2003 under the 

National Cooperative Highway Research Program (NCHRP) Project 20-59(2). 

In order to provide guidance to bridge owners, the Federal Highway Administrator appointed members to the Federal Highway Administration (FHWA)/AASHTO Blue Ribbon Panel 

(BRP) on bridge and tunnel security. Support for this initiative was provided at the request 

of the AASHTO Transportation Security Task Force. 

The following are the members of the BRP: 

•	 Mr. James E. Roberts, BRP Chair, Consulting Bridge Engineer, Imbsen and Associates, 

Inc. Dr. John M. Kulicki, BRP Vice Chair, President/CEO and Chief Engineer, Modjeski 

and Masters 

•	 Mr. Dwight Beranek, Deputy Director of Military Programs, U.S. Army Corps of 

Engineers 

•	 Mr. Joseph M. Englot, Assistant Chief Engineer/Design, Port Authority of New York 

and New Jersey 

•	 Dr. John W. Fisher, Professor Emeritus, Lehigh University 

•	 Mr. Henry Hungerbeeler, Director, Missouri Department of Transportation, and 

Chair, AASHTO Transportation Security Task Force 

•	 Dr. Jeremy Isenberg, President and CEO, Weidlinger Associates, Inc. 

•	 Dr. Frieder Seible, Dean, Jacobs School of Engineering, University of California at 

San Diego 

12	 A Guide to Highway Vulnerability Assessment for Critical Asset Identification and Protection prepared for AASHTO by Science Applications 

International Corporation, under NCHRP Project 20-7/151B, May 2002. AASHTO plans to refine and update this guide in 2004 to 

reflect more recent information and to include an economic impact tool that will assist states in identifying the most cost-effective 

vulnerability mitigation strategies. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

•	 Mr. Kenneth E. Stinson, Chairman and CEO, Peter Kiewit Sons, Inc. 

•	 Dr. Man Chung Tang, Chairman of the Board and Technical Director, T.Y. Lin 

International 

•	 Mr. Kary Witt, Bridge Manager and Deputy General Manager, Golden Gate Bridge, 

Highway and Transportation District 

FHWA’s charge to the panel was as follows: 

Develop short- and long-term strategies for improving the safety and 

security of the nation’s bridges and tunnels, and provide guidance to 

highway infrastructure owners/operators. 

The panel’s objective was to apply its collective experience and knowledge about structural 

design, structural integrity, and environmental stress and strain to new ways of examining 

how critical bridges and tunnels can be protected against potential terrorist attacks. 

The panel met four times to identify and clarify issues, develop and evaluate potential solutions, and formulate and refine recommendations for improving bridge and tunnel security. 

The recommendations presented in this report include recommendations on actions that 

can be taken either by bridge and tunnel owners and operators or by FHWA and other 

state and federal agencies that will result in improved security and reduced vulnerabilities 

for critical bridges and tunnels. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

2. Blue Ribbon Panel Approach 

2.1 Overall Strategy for Bridge and Tunnel Security — “The Bigger Picture” 

Bridge and tunnel security, like security for any infrastructure asset, includes a broad range 

of issues that must be addressed to ensure that adequate measures are taken to protect 

the asset and the people and goods that utilize the asset. Table 1 shows the bridge and 

tunnel security issues considered by the panel organized into topical areas. Several of the 

topics and related issues are of general interest and apply to all transportation infrastructure; others relate more directly to bridges and tunnels. For example, the “management and 

operational practices” issues apply to most infrastructure assets (transportation and otherwise), as do “information security,” “mobilization and response,” and “recovery” issues. 

However, issues that fall within the “planning, design, and engineering” area may be unique 

to bridges and tunnels and require special solutions that go beyond what might be needed 

to reduce the vulnerability and improve the security of other infrastructure assets. 

Table 1. Bridge and Tunnel Security Issues 

Key Topics in 

Infrastructure Security Specific Issues 

1. Foundations for Policy • Criteria Establishing Investment Priorities 

• Institutional Continuity 

2. Planning, Design, and Engineering • Design Review for Secure Structures 

• Research and Development (R&D) Needed 

to Support “Design for Security” 

• Design Criteria 

• Design Specifications 

3. Management and Operational Practices • Best Practices 

• Practice Review 

• Institutional Relationships 

• Preparedness 

• Personnel and Vehicle Security 

• Communication/Outreach 

4. Information Security • Procurement Practices 

• Information Security 

5. Mobilization (“Notice”) and Response 

(“Trans-event”) 

• Threat Warning 

• Early Response 

• Initial Response 

6. Recovery (Post-event) • Damage Assessment 

• Functional Continuity 

The panel’s special expertise is in the area of bridge and tunnel planning, design, and engineering; therefore, the primary focus of recommendations contained in this report addresses near- and long-term design and engineering solutions to bridge and tunnel vulnerabilities. 

9 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

2.2 Framework for Planning, Design, and Engineering 

During its initial meeting, the BRP established a framework for addressing bridge and tunnel 

security. This framework includes the following elements considered essential to developing 

sound recommendations for reducing bridge and tunnel vulnerability to terrorist attacks: 

•	 A means of identifying “critical” bridges and tunnels, through prioritization and risk 

assessment 

•	 Designation of the specific threats to be considered “terrorist attacks” (e.g., to 

eliminate military attacks with precision guided munitions) 

•	 Determination of the kinds of damage of concern (e.g., structural, contamination) 

•	 Countermeasures considered in response to potential threats and damage 

•	 The adequacy of current knowledge and available codes and specifications to enable 

design professionals to retrofit existing facilities and design hardened new facilities 

2.3 Prioritization and Risk Assessment 

A standardized, objective process is needed to identify those bridges and tunnels that are 

most likely to be targeted for a terrorist attack and the cost-effective projects to thwart 

the attack. Prioritization is the process of identifying the likely targets; risk assessment is the 

process by which methods of defeating the attack will be selected. Both are needed to 

establish a financial scope (i.e., to determine how much money it costs to deter and provide defense compared to the facility and social cost from the loss) and to allocate available 

funds appropriately. 

Therefore, the BRP advocates both of the following: 

•	 A prioritization method that could be based on subjective or empirical criteria and is 

accessible to a wide range of interested parties,13, 14 

•	 A risk assessment method that is based on rigorous engineering and mathematical 

principles accessible to experts and modeled after the methodology used for seismic 

studies by building on the risk methodology summarized in Section 4 of this report 

2.4 Threats 

Assessment of vulnerability requires consideration of the means of inflicting damage to a 

facility, that is, the threat or threats. The analogy to the conventional design process is the 

13	 These criteria should represent a consensus among stakeholders as to what makes a facility “important” in terms of an agency’s mission. In his April 1, 2003, testimony before the National Commission on Terrorist Attacks Upon the United States, G.L. Dillingham of 

the General Accounting Office states “A criticality assessment evaluates and prioritizes assets and functions in terms of specific criteria, such as their importance to public safety and the economy. The assessment provides a basis for identifying which structures or 

processes are relatively more important to protect from attack. As such it helps managers to determine operational requirements 

and to target resources to the highest priorities, while reducing the potential for targeting resources to lower priorities.” 

14	 The BRP recognizes that the AASHTO Guide to Highway Vulnerability Assessment for Critical Asset Identification and Protection is the current methodology and acknowledges it as a starting point for prioritizing bridges and tunnels; however, prioritization of bridges and 

tunnels requires more specific criteria and methods, such as those recommended later in this report. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

identification of the design loads. Effective countermeasures and associated costs cannot be 

developed without this assessment just as the amount of steel and concrete needed in a 

bridge or tunnel cannot be calculated if the loads are not known. The following types of 

threats are considered by the BRP:15 

•	 Low-tech and high-tech conventional explosives (e.g., shape charges) 

•	 Explosively formed penetrating devices (EFP, kinetic energy penetrators) 

•	 Low-tech, hand-held cutting devices 

•	 Truck size/barge size conventional explosives 

•	 Chemical/biological agents released in tunnels 

•	 Incendiary conventional explosives 

•	 HAZMAT release in tunnels 

•	 Intentional ramming via ship or barge 

2.5 Damage 

For the purposes of this report, the consequences of attack expressed as damage to 

bridges and tunnels that are of concern are as follows: 

•	 Threats to the integrity of the structure (e.g., resulting in replacement of the facility 

or major repairs) 

•	 Damage that inhibits the structure’s functionality for an extended period of time, 

such as closure of the facility for 30 days or more 

•	 Contamination of a tunnel resulting in extended closure or loss of functionality 

•	 Catastrophic failure resulting from an attack based on the threats described above 

2.6 Countermeasures 

If the process of prioritization and risk assessment leads to the conclusion that a given 

bridge or tunnel must be made more secure, there are a variety of countermeasures that 

can be used singly or in combination to reduce attractiveness and/or vulnerability, or to 

reduce consequences if an attack occurs. Countermeasures are often grouped into actions 

or technologies to deter attack, deny access, detect presence, defend the facility, or design 

structural hardening to minimize consequences to an accepted level. Because of its expertise, the BRP dealt primarily with the last category of countermeasures. The panel’s focus 

does not imply that other strategies for deterring, detecting and denying, or defending are 

not valid options. In many cases, risk assessment as recommended here will lead to the 

conclusion that one or more of the non-design countermeasures is the most appropriate 

15 Recognized experts from USACE presented background information on many of these types of threats to augment the knowledge 

within the panel. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

and cost-effective solution for a given facility. There are relatively mature technologies and 

strategies currently available for implementation. Application of these countermeasures still 

requires enabling funding but not necessarily the research and analysis commitment necessary to develop and implement effective design countermeasures. For completeness, a list 

of possible low-cost immediate actions to increase security exposure has been collected 

from several such sources and is appended here.16 

2.7 Codes and Specifications 

Considering consequences focuses attention on the ability to deal with the structural 

engineering ramifications. Some engineering guidance is available within the Department 

of Defense (DOD). However, the panel has determined that current design codes and 

specifications leave much to be desired in terms of how to employ hardening design, how 

to quantify blast-related demands, and how to determine the capacity of components 

exposed to high-pressure transients. 

Research agenda to fill in the gaps in current understanding of phenomena and response 

have been developed and are contained in Section 4. Given this basic knowledge, practical 

comprehensive design guidance and specifications can be developed as outlined here. 

16 See Appendix B for a list of commonly used operational security measures that fall into this category of countermeasures. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

3. Overarching Recommendations 

The seven overarching recommendations fall into three categories: institutional, fiscal, 

and technical. Recommendations in the first two areas are prerequisites to effective 

implementation of recommendations in the third area. These recommendations are 

as follows: 

3.1 Institutional Recommendations17 

•	 Interagency Coordination. Recognizing the importance of both operational and engineered solutions and the expertise that exists within the owner/operator community, FHWA, AASHTO, Transportation Security Administration (TSA), and other 

highway transportation stakeholders should collaborate to ensure that assessment 

methodologies and security solutions meet stakeholder needs. 

•	 Outreach and Communication Strategies. FHWA and AASHTO, in partnership with 

other organizations, should disseminate information (e.g., case studies, guidebooks, 

funding needs) about bridge and tunnel security and cost-effective countermeasures to decision-makers (federal agency leadership, e.g., DHS, U.S. Department 

of Transportation [USDOT], USACE), facility owners/operators, (state/local DOTs 

and authorities), designers (state DOTs, industry, academics), and elected officials 

(Congress, governors, mayors). Relationships already established through The 

Infrastructure Security Partnership (TISP) should be leveraged to facilitate 

outreach and implementation. 

•	 Clarification of Legal Responsibility. FHWA should seek to clarify the legal position of 

state DOTs and public transportation authorities with respect to their responsibility to act on the indications of risk studies for their facilities. State DOTs should 

be informed of legal precedent that will guide them in evaluating risk to facilities 

without becoming vulnerable to victims’ claims that knowledge was not translated 

into action soon enough. 

3.2 Fiscal Recommendations 

•	 New Funding Sources for Bridge/Tunnel Security. Bridge and tunnel security issues 

should be addressed with new funding provided beyond and outside of current 

federal-aid highway funding sources. These funds should come from the Department 

of Homeland Security (DHS). Transportation agencies are unable to keep up with 

national needs with current funding as identified in FHWA’s Conditions and 

Performance Report. 

17	 Since September 2001, federal, state, and local surface transportation agencies and the private sector have begun rethinking roles and 

responsibilities for transportation security. One challenge to achieving national preparedness hinges on the federal government’s ability to form effective partnerships among entities that implement security measures at the local level. Effective, well-coordinated partnerships require identifying roles and responsibilities; developing effective, collaborative relationships with local and regional transportation, emergency management, and law enforcement agencies; agreeing on performance-based standards that describe desired 

outcomes; testing procedures that implement roles and responsibilities; and sharing intelligence information. Testimony of G.L. 

Dillingham, General Accounting Office, before the National Commission on Terrorist Attacks Upon the United States, April 1, 2003. 

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Many states receive one-fourth to one-third of needed funding to preserve existing 

infrastructure. The trust fund must not be diverted.18 

•	 Funding Eligibility. To address the need for flexibility to fund critical structures on a 

programmatic basis, Title 23, Sections 144 and 133, should be amended to allow 

expenditures for cost-effective strategies for bridge security, as was done for seismic retrofitting. This change should allow federal funds to be expended on critical 

structures without regard to deficiency as currently defined. 

3.3 Technical Recommendations 

•	 Technical Expertise. Security solutions should be “engineered,” and FHWA, as the 

nation’s primary federal agency with the necessary engineering expertise, should 

collaborate with the TSA in its effort to prioritize critical bridges and tunnels and to 

administer fund allocation to responsible agencies to meet high priority security 

needs. This collaborative activity should produce a consistent risk model and costbenefit analysis approach. 

•	 Research, Development, and Implementation. Engineering standards do not exist 

regarding security concerns for bridges and tunnels. Technology (e.g., algorithms, 

materials, design tools, construction methods) should be developed and validated 

through appropriate R&D initiatives identified here to address this need. R&D 

efforts should lead to development of methods and standards to guide countermeasures design and implementation. Efforts should be taken to build on the knowledge 

base available from DOD and other agencies. The goal is to develop these tools and 

then adopt them into the appropriate AASHTO and other specifications. 

These seven overarching recommendations form the backbone of the BRP’s thinking 

regarding bridge and tunnel security. Although the panel believes that the fiscal and institutional recommendations offered above are essential to cost-effective bridge and tunnel 

security enhancement, the primary focus of this report is on the technical recommendations, reflecting both the primary objective of this effort and the collective strengths and 

expertise of the panelists. These technical recommendations include methods for identifying critical bridges and tunnels, operational security measures, engineering and design 

approaches for reducing the vulnerability of critical infrastructure, and related research 

and development needs. 

18	 In considering the federal government’s role in meeting long-term funding challenges, several issues will need to be addressed beyond 

determining who should pay for the security enhancements and to what extent the agency functions should be funded. An important consideration is, which criteria are most appropriate for distributing federal funds? The chief criteria considered have been ridership level, population, identified vulnerabilities, and criticality of assets. Another important consideration, as we reported in 

September 2002, is, which federal policy instruments — grants, loan guarantees, tax incentives, or partnerships — are most appropriate to motivate or mandate other levels of government or the private sector to help address security concerns? Finally, it will be 

important to consider how to allocate funds between competing needs and to measure whether we are achieving the increased security benefits envisioned. Testimony of G.L. Dillingham, General Accounting Office, before the National Commission on Terrorist 

Attacks Upon the United States, April 1, 2003.rity benefits envisioned. Testimony of G.L. Dillingham, General Accounting Office, before the 

National Commission on Terrorist Attacks Upon the United States, April 1, 2003. 

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All of the recommendations are to FHWA and AASHTO unless otherwise noted. The panel 

recognizes that several recommendations require collaboration with other federal agencies, 

in particular the Department of Homeland Security (DHS), and the panel encourages DHS 

to consider these recommendations. Recommendations that address policy foundations and 

institutional continuity are presented in Section 4. Technical design, engineering, and R&D 

recommendations are presented in Section 5. 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

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BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

4. Policy Foundations And Institutional 

Continuity 

4.1 Foundations for Policy and Planning 

Potential choices for dealing with risks associated with bridges and tunnels, in general 

terms, include the following: 

• Acceptance (no action) 

• Mitigation (retrofit, operational changes, add redundant facilities) 

• Transfer (insurance, self-insurance, or other financial instruments) 

The criteria for making choices related to these facilities will be applied at the national, 

regional, or local level. Owners of facilities are using existing technology and information to 

enhance the security of critical assets by diverting program funds away from maintenance 

and construction until federal funds are available specifically for security. The goal of policy 

is to develop and encourage the use of consistent prioritization and risk assessment methods leading to actions that will enhance bridge and tunnel security. 

Assessment 

In the near-term, the primary basis for prioritization and risk assessment is the National Bridge 

Inventory System (NBIS) maintained by FHWA. NBIS contains data about bridges (no tunnel 

data), including location, structure type, span characteristics, average daily traffic volume, military significance, and other use-related information. This data can help inform the decision 

process for selecting high priority bridges for near-term security countermeasures. 

Recommendations 

Near-term (3-6 months): 

1.	 FHWA should engage AASHTO, through its standing committee structure, informed by 

current information such as studies, reports, and briefings, to review and comment on 

proposed funding programs to improve bridge/tunnel security against terrorist attacks. 

This activity should be supported through AASHTO, NCHRP, FHWA, or other national 

funding sources to offset travel and other meeting expenses. 

2.	 FHWA should summarize the current status of critical bridges and tunnels identified 

through previous studies. 

Mid-term (6-12 months): 

1.	 FHWA should collaborate with the TSA and other stakeholders to develop a bridge 

and tunnel prioritization process based on the methodology outlined in Section 5. 

2.	 FHWA should develop guidelines for applying the prioritization approach, including 

illustrative examples and technical assistance. 

3.	 FHWA should issue a FHWA Technical Advisory on how to implement available and applicable technology and procedures to enhance bridge and tunnel security, including potential 

funding sources, technical contacts, streamlined procurement, and other information. 

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Long-term (12-18 months): 

1.	 FHWA should encourage application (via solicitation/response cycle) and refinement of 

processes through a centralized “clearinghouse” where results are used to improve processes. 

4.2 Institutional Continuity 

Continuity is necessary to ensure implementation and periodic evaluation by a recognized, 

credible, representative, and relevant national organization empowered to deal with 

Security Sensitive Information (SSI) and promulgate policies and specifications. A forum for 

information exchange among entities responsible for surface transportation security would 

help to provide this continuity. 

The Transportation Security Administration (TSA) is developing risk assessment methodologies and countermeasures for all transportation modes. The BRP encourages TSA to 

leverage FHWA and state DOT and facility owner/operator experience in vulnerability 

assessment and security measures so that TSA methodologies reflect the needs of DOTs 

and facility owner/operators as well as the homeland security needs of the nation. 

Assessment 

The panel recognizes that policy guidance for transportation security will be formulated as 

a collaborative effort among TSA, FHWA, AASHTO, and other highway transportation 

stakeholders. The panel recognizes that AASHTO is the most appropriate organization for 

implementing security policy within the highway bridge and tunnel community. 

Recommendations 

Near-term (3-6 months): 

1.	 Recognizing the importance of both operational and engineered solutions and the 

expertise that exists within the owner/operator community, FHWA, AASHTO, TSA, 

and other highway transportation stakeholders should collaborate to ensure that 

assessment methodologies and security solutions meet stakeholder needs. 

2.	 It is assumed that TSA will promulgate top-level performance-based design guidance. 

Detailed implementation strategies should be developed by FHWA, AASHTO, and 

other sources of technical expertise. 

3.	 With respect to highway bridges and tunnels, an AASHTO entity is the most appropriate organization to address security issues.19 

4.	 Recognizing that many facilities have dual use, and working with TSA, a dialogue should 

be established between the AASHTO Technical Committee and similar entities representing rail organizations (AAR) and transit providers (APTA) responsible for similar 

structures and operations. 

19	 At its first meeting, the BRP recommended that the AASHTO Standing Committee on Bridges and Structures (SCOBS) form a new 

permanent Technical Committee on Bridge and Tunnel Security. This recommendation was acted upon immediately. Technical 

Committee T-1 was to have its first meeting at the June 2003 SCOBS meeting. The panel encourages the AASHTO SCOBS to engage 

other bridge and tunnel stakeholders in its activities. 

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5. Planning, Design, and Engineering 

Recommendations 

Because of its heterogeneity in size and operations and the multitude of owners and operators nationwide, the transportation infrastructure network in the United States is highly 

resilient, flexible, and responsive.14 Unfortunately, the sector is fractionated and regulated 

by multiple jurisdictions at state, federal, and sometimes local levels. The size and pervasive 

nature of the U.S. transportation infrastructure poses significant protection challenges.20 

However, these protection challenges can be mitigated through technical collaboration and 

coordination. 

5.1 Review and Prioritization Process 

A process is necessary for prioritizing all bridges and tunnels with respect to their vulnerability in terms of their criticality of the ability to deter, deny, detect, delay, and defend against 

terrorist attacks. In addition, a risk assessment model must be developed as a framework 

for evaluating alternatives for thwarting attack. 

Several agencies have developed methods for identifying and prioritizing critical transportation 

assets, and these methods share many commonalities. The prioritization procedure outlined 

in the AASHTO’s methodology uses a set of critical asset factors to identify assets that are 

important to achieving an agency’s mission. Next, the AASHTO methodology assesses the 

vulnerability of these critical assets to terrorist attack based on target attractiveness (potential casualties and symbolic value); accessibility (access controls and physical security); and 

expected damage (including environmental hazards).21 The TSA approach determines relative 

risk as a function of relative target attractiveness (an assessment of the target’s importance 

and consequences); relative likelihood of occurrence (an assessment by TSA Intelligence of 

the likelihood of occurrence, as compared to the other scenarios); and vulnerability (a 

measure of how likely the terrorist is to achieve the threatening act given that an attempt 

is made). Relative risk is re-calculated based upon the implementation of a suite of countermeasures, including the implementation of people, procedures, and/or technology to 

reduce vulnerability.22 

20	 Transportation choke points (e.g., bridges and tunnels, inter-modal terminals, border crossings, and highway interchanges) present 

unique protection challenges. Overall understanding of infrastructure choke points is limited. Common criteria for identifying critical choke points are therefore difficult to establish. We must undertake a comprehensive, systematic effort to identify key assets, particularly those whose destruction or disruption would entail significant public health and safety consequences or significant economic impact. . . . A major reason for this lack of synchronization within the sector is a paucity of funds to promote communication among 

industry members and facilitate cooperation for joint protection planning efforts. As a result, the sector as a whole has neither a 

coherent picture of industry-wide risks, nor a set of appropriate security criteria on which to baseline its protection planning efforts, 

such as what conditions constitute threats for the sector, or standards for infrastructure protection or threat reduction. The sector’s diverse and widely distributed constituency complicates this situation. The National Strategy for the Physical Protection of Critical 

Infrastructures and Key Assets, The Office of the United States White House, Washington D.C., 2003. 

21	 A Guide to Highway Vulnerability Assessment for Critical Asset Identification and Protection, prepared for AASHTO by Science Applications 

International Corporation, under NCHRP Project 20-7/151B, May 2002. 

22	 Briefing to the FHWA/AASHTO Blue Ribbon Panel on Bridge and Tunnel Security presented by Tom Reilly, Transportation Security 

Administration, Department of Homeland Security, March 27, 2003. 

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Assessment 

The panel considered and rejected several options: 

1.	 Do nothing, which the panel found unacceptable under post-September 11th threats. 

2.	 Have states conduct their own assessment using prioritization and risk assessment 

methodologies of their own choice. This is unacceptable because federal funds will be 

required to meet countermeasure needs and the federal government will need a common, uniform, and consistently applied methodology to compare needs. 

3.	 The federal government conducts assessment throughout all the states. This is unacceptable because it does not take into account states’ operating needs, and the states 

are much more knowledgeable in assessing their own bridge and tunnel assets. 

Because national prioritization of funding will be required, the process of evaluating proposals to enhance bridge and tunnel security must be a joint effort by federal and state agencies and other owners and operators. 

The large number of bridges (600,000) and tunnels (500) lends itself to a two-tier 

approach: prioritization and risk assessment. The first tier, prioritization, is typically most 

efficiently done in two steps. The first step is a data-driven approach, such as that used by 

the Texas Department of Transportation (TxDOT), for ranking bridges using common criteria.23 The National Bridge Inventory (NBI) provides much of the data needed for this step. 

In the second step of prioritization, additional data comes from owners and operators 

familiar with specific characteristics of the facilities and the services they provide. In this 

first tier ranking, prioritization of bridges and tunnels should be based on characteristics 

such as the following: 

•	 Potential for mass casualty based on Average Daily Traffic (ADT) and associated 

peak occupancies 

•	 Criticality to emergency evacuation and response to emergencies 

•	 Military or defense mobilization 

•	 Alternative routes with adequate available capacity 

•	 Potential for extensive media exposure and public reaction; symbolic value (to 

what extent does the facility represent ideals and values that are important to the 

American public, also visual symbolism, e.g., “signature bridges”) 

•	 Mixed-use bridges and tunnels where highway and rail are co-located 

•	 Potential for collateral damage (land, marine, rail), including collateral property 

and utilities 

•	 Maximum single span length as it relates to the time required to replace the facility 

23	 “Transportation Security Update,” briefing presentation by Tom Rummel, P.E., Project Development Section, Bridge Division, Texas 

Department of Transportation, February 2003. 

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•	 Commercial vehicle vs. passenger vehicle mix and volume as a surrogate for 

economic impact 

•	 Bridge or tunnel dimensions (as a surrogate for replacement time/cost) 

•	 Significance of revenue streams (e.g., tolls, fares) associated with the facility24 

•	 Bridges and tunnels at international border crossings 

The second tier is a risk assessment of high priority bridges taken from the first tier (prioritization) to determine vulnerabilities and evaluate countermeasures to deter attack and/or 

mitigate damages. The risk, R, to the facility is determined following an approach similar to 

that developed for seismic retrofit and can be expressed as follows:25 

R = O x V x I 

where, 

O = Occurrence: In the general form of the risk equation, this factor is hazard oriented 

and will change with the nature of the hazard. In the context of this report, the occurrence factor approximates the likelihood that terrorists will attack the asset. It includes 

target attractiveness (from the perspective of the threat), level of security, access to 

the site, publicity if attacked, and the number of prior threats. Input into this factor 

typically comes from the law enforcement and intelligence communities familiar with 

threat and operational security measures. 

V = Vulnerability: In the general form of the risk equation, vulnerability is an indication of how much the facility or population would be damaged or destroyed based on 

the structural response to a particular hazard. In the context of this report, vulnerability is the likely damage resulting from various terrorist threats (weapon type and location). It is a measure of expected damage, outcome of the event, expected casualties, 

and loss of use, all features of the facility itself. Input into this factor typically comes 

from engineering analysis and expertise. 

I = Importance: Importance is a characteristic of the facility, not the hazard. In principle, 

importance is the same for any hazard. Importance is an indication of consequences to 

the region or nation in the event the facility is destroyed or unavailable. Is the facility on 

an evacuation or military mobilization route; is it likely to be used by first responders 

to emergencies; what is its historic and associated significance; what is its peak occupancy? Input into this factor typically comes from owners, operators, users, and beneficiaries of the facilities, often governmental sources, and will use factors similar to those 

used in the first tier prioritization. 

24	 Revenue streams associated with facilities may not make them attractive targets, but their loss could seriously affect the economic 

viability of entities that depend on revenue derived from them to maintain continuity of operations. 

25	 The proposed approach is consistent with the approach suggested by the TSA and with approaches currently used by entities that 

have completed or are performing risk assessments. 

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This formula properly expresses the interaction among the three factors. Dominant factors 

magnify risk; negligible factors diminish it. Other formulas, such as models that add the factors, fail to account for their interactive effects. For example, in the absence of a threat 

(‘O’=0), the risk should be zero as this model provides; additive models would have a residual 

risk. In the multiplicative model, eliminating any one factor to zero (or near zero) reduces the 

risk to near zero (e.g., low importance leads to low risk regardless of other factors). 

The countermeasures that reduce the risk associated with an asset may be designed to 

reduce the occurrence factor (e.g., make the asset less accessible); the vulnerability factor 

(e.g., harden the facility to reduce damage); or the importance factor (e.g., add redundant 

facilities to reduce dependence on the asset). 

A case study illustrating application of this risk assessment approach to bridges and tunnels 

is provided in Appendix C. 

Recommendations 

The panel recommends a state identification and prioritization of bridges and tunnels, followed by a federal re-prioritization for federal funding based on the following: 

Near-term (3-6 months): 

1.	 FHWA determines and promulgates a methodology for reviewing bridges and tunnels 

with respect to their risk and vulnerability in terms of their ability to detect, deny, 

delay, and defend against terrorist attacks. Methodologies that may be considered 

should be developed and include the AASHTO Guide for Highway Vulnerability Assessment, 

the Texas DOT methodology, and others. 

2.	 Using methodology promulgated by the FHWA similar to that described above, states 

should prioritize their bridges and tunnels and submit prioritized lists of their most 

critical bridges and tunnels to FHWA. 

3.	 FHWA/AASHTO should oversee the development of an immediate, near-, and midterm cost-benefit methodology based on probabilistic risk assessment for implementing countermeasures. Within the framework of probabilistic risk assessment of the 

kind that has been adopted for seismic retrofit programs, consideration should be 

given to existing methodologies. 

Mid-term (6-12 months): 

1.	 FHWA takes states’ priority lists of critical bridges and tunnels and develops a national 

list of critical bridges and tunnels. 

2.	 States use the risk assessment methodology to develop a countermeasures plan using 

a cost-benefit ratio as a metric and provide costs for implementing countermeasures 

for each of their critical bridges and tunnels to FHWA. 

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Long-term (12-18 months): 

1.	 FHWA, in collaboration with DHS/TSA and other agencies, seeks new appropriations 

from Congress to implement a national bridge and tunnel countermeasure program. 

FHWA begins allocating funds to the highest priority bridges and tunnels as identified by 

the states and other owners/operators in accordance with accepted risk assessment 

methodologies. 

2.	 Non-state DOT bridge and tunnel owners begin implementing countermeasures consistent with federal security standards using appropriate funding sources, including federal sources where applicable. 

3.	 FHWA in coordination with AASHTO develops and implements modifications to existing 

bridge and tunnel inspection programs to evaluate conformance to federal security standards. 

4.	 States implement countermeasures with funding as available. One source recommends 

an initial sum of at least $1.5 billion to address near-term security measures.26 

5.2 Research and Development 

Assessment 

The analysis of current structural components and their behavior to blast loads is recognized by the panel as key to understanding the proper and most efficient ways to mitigate 

terrorist attacks through structural design and retrofit. Table 2 lists key structural bridge 

components that the panel considered. 

Table 2. Critical Bridge Components 

Suspension and CableStayed Bridges Truss Bridges Arch Bridges 

• Suspender ropes, stay 

cables 

• Tower leg 

• Main cable 

• Orthotropic steel deck 

• Reinforced and prestressed 

bridge decks 

• Cable saddle 

• Approach structures 

• Connections 

• Anchorage 

• Piers 

• Suspended span hangers 

• Continuous and cantilever 

hold-down anchorages 

• Compression chords or 

diagonals 

• Connections 

• Decks 

• Piers 

• Tension-tie 

• Connections 

• Decks 

• Piers 

Multi-girder/Freeway 

Overpass Bridges 

• Decks 

• Connections 

• Piers 

National Needs Assessment for Ensuring Transportation Infrastructure Security, prepared by Douglas B. Ham and Stephen Lockwood, 

Parsons Brinckerhoff, for the American Association of State Highway and Transportation Officials (AASHTO) Transportation Security 

Task Force as part of NCHRP Project 20-59, Task 5, October 2002. 

23 

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Recommendations 

The goal of the R&D initiatives recommended here is to create empirically validated computational tools, design methods, and hardening technologies to assist in “designing for the 

terrorist attack.” The recommendations have one or more short-term and long-term elements and all are directed to FHWA, AASHTO, and other government-sponsored research 

activities, including universities and federal laboratories. Additionally, these five recommendations are interrelated and interdependent and should be pursued simultaneously: 

1.	 Assess performance of critical elements under credible loads (including load reversals) 

Short-term (within the next year): 

•	 Synthesize current state of knowledge for component properties and modeling 

Long-term (more than one year): 

•	 Establish the load structure and load interaction 

•	 Start component experiments; recommend large-scale testing using real materials, 

components, and connections under comparable strain rates 

•	 Conduct comparative parameter studies of typical components and materials 

2.	 Validate and calibrate computational methods and modeling with experiments to better understand structural behavior from blast loads 

Short-term (within the next year): 

•	 Pull together and examine studies and research that have already been conducted 

on bridge and tunnel elements and components 

•	 Investigate transferability of seismic design 

Long-term (more than one year): 

•	 Develop a predictive round robin analysis of actual blast experiments on bridge 

and tunnel components 

•	 Test critical components, such as suspender ropes, stay cables, concrete and steel 

decks, side loads on towers, and box sections, for testing and blast performance 

3.	 Validate and calibrate computational methods and modeling with experiments to better understand structural behavior from thermal loads 

Short-term (within the next year): 

•	 Pull together and examine studies and research that have already been conducted 

on bridge and tunnel elements and components 

Long-term (more than one year): 

•	 Evaluate various mitigation fire effects in tunnels, double deck bridges, and overpass bridges 

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4.	 Determine the residual functionality of bridge and tunnel systems and their tolerance 

for extreme damage 

Short-term (within the next year): 

•	 Examine bridges and tunnels compromised in wars and after demolition attempts 

Long-term (more than one year): 

•	 Determine progressive collapse potential of various bridge and tunnel systems 

5.	 Develop mitigation measures and hardening technologies 

Short-term (within the next year): 

•	 Assess existing hardening technologies and the applicability to bridges and tunnels 

Long-term (more than one year): 

•	 Develop new materials and new design methodologies 

In addition to these R&D recommendations, the BRP suggests AASHTO work with university engineering institutions to develop R&D programs for students and bridge professionals 

to address security concerns. The panel recommends that DHS work jointly with industry 

and state and local governments to explore and identify potential technology solutions and 

standards that will support analysis and afford better and more cost-effective protection 

against terrorism.27 

5.3 Design Criteria 

Assessment 

The acceptability of a threat is the criterion for determining how to design for the threat. 

Performance level design is based stating assumptions and setting expectations and goals. 

These factors could include threats, casualties, damage, and recovery. To set a performance 

level design criteria, the design process must first be described, taking into account the 

potential threats to the existing or planned bridge or tunnel. The panel recommends that 

bridge and tunnel owners and operators use the following six-step process:28 

1.	 Use previously determined “R,” the risk for each bridge or tunnel, whether existing or 

planned, determined using the R = OVI model. 

a.	 Determine Threats. There are several potential threats that exist. The first and most 

serious is a precision demolition attack. If carried out, this attack will destroy or 

seriously damage the bridge or tunnel. Therefore, this threat must be mitigated so 

that it will not be allowed to happen. Other threats to consider are conventional 

explosives, collision, and fire. Their potential magnitude is presented in Table 3. 

27	 One recommendation related to transportation infrastructure is to “harden industry infrastructure against terrorism through technology. DHS will work jointly with industry and state and local governments to explore and identify potential technology solutions 

and standards that will support analysis and afford better and more cost effective protection against terrorism.” The National Strategy 

for the Physical Protection of Critical Infrastructures and Key Assets, The Office of the United States White House,Washington D.C., 2003. 

28	 See Appendix C for a case study of the application of this design methodology. 

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Table 3. Magnitude of Threats 

Threat Type Largest Possible Highest Probability 

Conventional explosives Truck*: 20,000 lbs 

Barge: 40,000 lbs 

Car bomb*: 500 lbs 

Collision to structure (i.e., the size 

of a vehicle that could collide with 

a structure) 

Truck: 100,000 lbs 

GVW 

Water Vessel: depends on waterway 

Truck: H-15 

Water Vessel: (see AASHTO spec. 

LRFD on vessel impact) 

Fire Largest existing fuel or 

propane tank 

Largest fuel vessel or tanker 

Gasoline truck (3S-2) 

Fuel barge 

Chemical/biological HAZMAT These threats exist; however, the panel is not qualified to quantify them. 

Therefore, other experts should assess these threats in this way. 

*	 Largest possible conventional explosive – for a truck, based on largest truck bomb ever detonated internationally by a terrorist act. 

For a barge, based on the assumption that it is the largest explosive that could pass by unnoticed by current security at place at 

major waterways. 

**	 The size of an explosive charge that can be concealed within the trunk of an automobile without being visually detected when inspecting 

the automobile. 

b.	 Determine the Consequence. Based on the potential threats to the bridge or 

tunnel, the owner must decide the potential consequences if carried out. 

2.	 Determine the acceptability of consequences. If the consequences are acceptable, then 

the owner may decide to do nothing. 

3.	 If the consequences are unacceptable, then one of two options exists: 

a.	 Mitigate the Threat. Generally, these actions can be taken in the short term 

(3-6 month range). Owners should take measures to lessen the attractiveness or 

deny access through technology, operational procedures, and physical measures. 

b.	 Mitigate the Consequence. These actions fall into the mid- to long-term time frame. 

Reduce the damage and resulting loss of life, property, functionality, and economic 

viability through design, engineering, and operational strategies. 

This step in the process requires detailed engineering analysis, vulnerability assessments, 

and statistical analysis of specific facilities and postulated threats to those facilities. 

4.	 Estimate the cost of mitigating the threat or consequence. 

5.	 Recalculate the R=OVI based on the recommended mitigation approach to determine 

the risk reduction achieved. 

a.	 Assets that receive a high R score should be categorized as a “high priority” structure. 

Steps should be taken to mitigate the largest possible threat in this situation. Designs 

should be performed so that in the event of this threat there would be no irreparable 

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damage and the structure could return to operable condition in 30 days. Higher probability threats should be designed so that in event of threat there is not loss of service. 

b.	 Assets that receive a low R score should be categorized as a “low priority” structure. The criteria for these structures in the event of the largest possible threat is 

that total loss is acceptable. The destruction of these low priority assets will not 

be devastating to the region because of alternative routes, size, economic implications, and socio-political messages. Higher probability threats should be designed 

so that in the event of threat there is minimal loss of service. 

6.	 Compare the costs and benefits (risk reduction) of varying mitigation combinations 

and strategies under designated analysis scenarios. In determining the cost and benefits 

associated with various mitigation strategies and countermeasures, the analysis should 

include cost related to increased user cost and potential environmental/energy cost 

effects if the facility were destroyed or seriously damaged. 

As an alternative possibility for acceptability criteria guidance, the bridge owner may consider what sort of time frame it can handle for loss of service. For example, if the time frame is 

13 days, then the bridge owner can determine what sort of threat type (from car, boat, etc., 

or size of explosives) could potentially do this damage, and mitigate for this threat. 

The recommendations for design criteria are based on various mitigating strategies. 

Owners have the choice to mitigate the threat (preventing terrorists facility access), mitigate the consequence effect (lessening the effect from an attack), or apply both options. 

The following are examples of approaches to mitigate threats: 

•	 Establishing a secure perimeter using physical barriers 

•	 Inspection surveillance, detection and enforcement, closed circuit television (CCTV) 

•	 Visible security presence 

• Minimize time on target 

The following are examples of approaches to mitigate consequences: 

•	 Create Standoff Distance. The first level of mitigating terrorist attacks should be 

to incorporate sufficient standoff distances from primary structural components. 

Providing standoff distance is highly recommended. There are three basic approaches to 

blast resistant design: increasing standoff distances; structural hardening of members; or 

higher acceptable levels of risk. Often, utilizing a percentage of each strategy is optimal. 

•	 Add Design Redundancy. Structural systems that provide great redundancy 

among structural components will help limit collapse in the event of severe structural damage from unpredictable terrorist acts. 

•	 Hardening/Strengthening the Elements of the Structure. Structural retrofitting and hardening priority should be assigned to critical elements that are essential to mitigating the extent of collapse. Secondary structural elements should be 

dealt with to minimize injury and damage. 

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•	 Develop an Accelerated Response and Recovery Plan. Alternative routes 

and evacuation plans should be known and established. 

Recommendations 

FHWA, in collaboration with AASHTO and TSA, should use the countermeasures development 

and evaluation methods described in this section to assess countermeasure effectiveness. 

Typical countermeasures to be considered are shown below and in Appendix A. 

Countermeasures should be ranked and implemented based on the cost-benefit analysis 

approach described here. 

5.4 Technology Development And Dissemination 

The overall objectives in the area of technology development and dissemination are to: (1) 

develop a bridge and tunnel security technical program, including cost estimates and 

resources; and (2) develop an educational curriculum for students and bridge professionals. 

Assessment 

The panel has determined that a sufficient body of knowledge exists to assemble an interim 

structural assessment/design guide based on the following: 

•	 Existing blast software 

•	 Strain-rate based constitutive laws or resistance adjustments 

•	 Ductility/deformation limits 

•	 Existing plastic design of steel and Ultimate Strength Design (USD) of concrete, 

adjusted as indicated in (1), (2), and (3) above 

Recommendations 

1.	 FHWA and AASHTO, in collaboration with the USACE and DHS/TSA and others, collect and synthesize existing information, analyses, and case studies and prepare interim 

findings to support quantitative analysis of blast effects, structural response, and countermeasures cost-effectiveness. These findings should include points of contact (agencies, firms, and individuals) with specific expertise in bridge and tunnel blast analysis. 

2.	 The panel recommends that AASHTO and FHWA endorse The National Pooled Fund 

Project, TPF-5(056), Design of Bridges for Security, TxDOT Project No. 0-4569, August 

15, 2002. 

3.	 The BRP recommends that AASHTO work with university engineering institutions 

to develop an educational curriculum for students and bridge professionals to address 

security concerns. AASHTO should consider supporting the “Educational Bridge” 

program sponsored by the National Society of Professional Engineers (NSPE) in collaboration with TISP though which universities are being encouraged to integrate 

infrastructure security into their curricula. 

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6. Recommendations Summary 

This section summarizes recommendations made by the BRP. Sub-sections 6.1, 6.2, and 6.3 

summarize short-, mid-, and long-term strategies, respectively, for improving bridge and 

tunnel security. Sub-section 6.4 summarizes design guidance for facility owners/operators 

to use in mitigating threats to facilities or the consequences of an attack on facilities. Subsection 6.5 gives the BRP concluding observations and overall recommendations for moving 

forward in addressing bridge and tunnel security issues. 

6.1 Short-term Strategies for Improving Bridge and Tunnel Security 

Policy and Planning 

•	 FHWA should engage AASHTO, through its standing committee structure, informed 

by current information (studies, reports, briefings), to review and comment on proposed funding programs to improve bridge/tunnel security against terrorist attacks. 

This activity should be supported through AASHTO, NCHRP, FHWA, or other 

national funding sources to offset travel and other meeting expenses. 

•	 FHWA should summarize the current status of critical bridges and tunnels identified 

through previous studies. 

Institutional Continuity 

•	 Recognizing the importance of both operational and engineered solutions and the 

expertise that exists within the owner/operator community, FHWA, AASHTO, TSA, 

and other highway transportation stakeholders should collaborate to ensure that 

assessment methodologies and security solutions meet stakeholder needs. 

•	 It is assumed that TSA will promulgate top-level performance-based design guidance. 

Detailed implementation strategies should be developed by FHWA, AASHTO, and 

other sources of technical expertise. 

•	 With respect to highway bridges and tunnels, an AASHTO entity is the most appropriate organization to address security issues. 

•	 Recognizing that many facilities have dual use, and working with TSA, FHWA should 

establish dialogue between the AASHTO Technical Committee and similar entities 

representing rail organizations (AAR) and transit providers (APTA) responsible for 

similar structures and operations. 

Review and Prioritization 

•	 FHWA should determine and promulgate a methodology for reviewing bridge and 

tunnel risks and vulnerabilities with respect to detecting, denying, delaying, and 

defending against terrorist attacks. FHWA should develop methodologies that may 

be considered and include the AASHTO Guide for Highway Vulnerability Assessment, the 

Texas DOT methodology, or others. 

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•	 Using methodology promulgated by FHWA similar to that described here, states 

should prioritize their bridges and tunnels and submit prioritized lists of their most 

critical bridges and tunnels to FHWA. 

•	 FHWA/AASHTO should oversee the development of an immediate, near-, and midterm cost-benefit methodology based on probabilistic risk assessment for implementing countermeasures. Within the framework of probabilistic risk assessment of 

the kind that has been adopted for seismic retrofit programs, consideration should 

be given to existing methodologies. 

Research and Development 

•	 FHWA should synthesize the current state of knowledge for component properties 

and modeling of critical elements under credible loads (including load reversals). 

•	 FHWA should pull together and examine studies and research that have already 

been conducted on bridge and tunnel elements and components as a first step 

toward validating and calibrating computational methods and models to understand 

structural behavior from blast and thermal loads. 

•	 FHWA should investigate transferability of seismic design. 

•	 FHWA, in collaboration with other research partners, should examine bridges and 

tunnels compromised in wars and after demolition attempts to determine residual 

functionality of bridge and tunnel systems and their tolerance for extreme damage. 

•	 FHWA should assess existing hardening technologies and their applicability to 

bridges and tunnels. 

Technology Development and Dissemination 

•	 FHWA and AASHTO, in collaboration with the USACE and DHS/TSA and others, 

should collect and synthesize existing information, analyses, and case studies and 

prepare interim findings to support quantitative analysis of blast effects, structural 

response, and countermeasures cost-effectiveness. These findings should include 

points of contact (agencies, firms, and individuals) with specific expertise in bridge 

and tunnel blast analysis. 

•	 The panel recommends that AASHTO and FHWA endorse The National Pooled Fund 

Project, TPF-5(056), Design of Bridges for Security, TxDOT Project No. 0-4569, August 15, 

2002. 

•	 The BRP recommends that AASHTO work with university engineering institutions 

to develop an educational curriculum for students and bridge professionals to 

address security concerns. Consider supporting the “Educational Bridge” program 

sponsored by NSPE in collaboration with TISP though which universities are being 

encouraged to integrate infrastructure security into their curricula. 

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6.2 Mid-term Strategies for Improving Bridge and Tunnel Security 

Policy and Planning 

•	 FHWA should collaborate with the TSA and other stakeholders to develop a bridge 

and tunnel prioritization process based on the methodology outlined in Section 5.1. 

•	 FHWA should develop guidelines for applying the prioritization approach, including 

illustrative examples and technical assistance. 

•	 FHWA should issue an FHWA Technical Advisory on how to implement available 

and applicable technology and procedures to enhance bridge and tunnel security, 

including potential funding sources, technical contacts, streamlined procurement, 

and other information. 

Review and Prioritization Process 

•	 FHWA takes states’ priority lists of critical bridges and tunnels and develops a 

national list of critical bridges and tunnels. 

•	 States use the risk assessment methodology to develop a countermeasures plan 

using cost-benefit ratio as a metric and provide costs for implementing countermeasures for each of their critical bridges and tunnels to FHWA. 

6.3 Long-term Strategies for Improving Bridge and Tunnel Security 

Policy and Planning 

•	 FHWA should encourage application (via solicitation/response cycle) and refinement 

of prioritization and risk assessment processes through a centralized “clearinghouse” 

where results are used to improve processes. 

Review and Prioritization Process 

•	 FHWA, in collaboration with DHS/TSA and other agencies, seeks new appropriations from Congress to implement a national bridge and tunnel countermeasure 

program. FHWA begins allocating funds to the highest priority bridges and tunnels 

as identified by the states and other owners/operators in accordance with accepted 

risk assessment methodologies. 

•	 Non-state DOT bridge and tunnel owners begin implementing countermeasures 

consistent with federal security standards using appropriate funding sources, including federal sources where applicable. 

•	 FHWA, in coordination with AASHTO, develops and implements modifications to 

existing bridge and tunnel inspection programs to evaluate conformance to federal 

security standards. 

•	 States implement countermeasures with funding as available. One source recommends an initial sum of at least $1.5 billion to address near-term security measures. 

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Research and Development 

•	 FHWA should establish the load structure and load interaction for the performance 

of critical elements under credible loads. 

•	 FHWA should start component experiments; recommend large scale testing using 

real materials, components, and connections under comparable strain rates. 

•	 FHWA should conduct comparative parameter studies of typical components and 

materials. 

•	 FHWA should develop a predictive round robin analysis of actual blast experiments 

on bridge and tunnel components. 

•	 FHWA should test critical components, such as suspender ropes, stay cables, concrete and steel decks, side loads on towers, and box sections, for testing and blast 

performance. 

•	 FHWA should evaluate various mitigation fire effects in tunnels, double deck 

bridges, and overpass bridges. 

•	 FHWA should determine the progressive collapse potential of various bridge and 

tunnel systems. 

•	 FHWA should develop new materials and new design methodologies. 

6.4 Design Criteria/Guidance to Highway Infrastructure Owners/Operators 

Mitigate Threats 

•	 Establishment of a secure perimeter using physical barriers 

•	 Inspection surveillance, detection and enforcement, CCTV 

•	 Visible security presence 

•	 Minimized time on target 

Mitigate Consequences 

•	 Create Standoff Distance (Highly Recommended). The first level of mitigating terrorist attacks should be to incorporate sufficient standoff distances from primary structural components. There are three basic approaches to blast resistant 

design: increasing standoff distances, structural hardening of members, or higher 

acceptable levels of risk. Often, utilizing a percentage of each strategy is optimal. 

•	 Add Design Redundancy. Structural systems that provide great redundancy 

among structural components will help limit collapse in the event of severe structural damage from unpredictable terrorist acts. 

•	 Harden/Strengthen the Elements of the Structure. Structural retrofitting 

and hardening priority should be assigned to critical elements that are essential to 

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mitigating the extent of collapse. Secondary structural elements should be dealt 

with to minimize injury and damage. 

•	 Develop an Accelerated Recovery Plan. Alternative routes and evacuation 

plans should be known and established. 

6.5 Conclusions 

•	 Bridge and tunnel security is important enough to be a matter of national security 

policy. The threat is real: attacks at choke points could be devastating. 

•	 Operational security measures are in place and well known to bridge and tunnel 

operators who operate “signature” facilities. Additional outreach and education are 

needed to expand both the body of knowledge about operational procedures and the 

knowledge and expertise of facility owners and operators. Site improvements and operational procedures will often prove more cost effective than structural engineering solutions. 

•	 Bridge and tunnel security require the institutional, technical, and fiscal responses 

recommended by the BRP in the overarching recommendations. Interagency cooperation is necessary for the development of cost-effective and implementable policies 

and standards. New funding must be made available to be able to deal with security issues 

and still allow for needed maintenance and expansion of the current highway system. 

•	 Proven tools are needed to set priorities and allocate resources, evaluate “designfor-security” approaches, and assess countermeasure effectiveness. As big as the 

problem appears to be, it may be made manageable through prioritization and risk 

assessment. 

•	 Research is needed to assess structural responses and to validate and calibrate 

computational methods and models. Structural engineering guidance needs to be developed by expanding on work done by DOD through research leading to design guidance. 

•	 Outreach and education are needed to develop greater awareness and professional 

capacity to address bridge and tunnel security challenges. We need trained professionals 

to understand and meet these challenges. 

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Appendix A: Countermeasure Options29 

The countermeasures listed below are available to bridge and tunnel owners and operators 

for their use in planning and implementing more effective security practices. The list is 

provided in the interest of sharing information that may prove helpful to individuals and 

agencies, but the panel does not recommend specific countermeasures or their application 

to specific facilities. 

Planning and coordination measures 

Update the emergency operations plan/crisis management plan to include response and 

recovery to a terrorist threat involving a bridge. Based on the Federal Emergency 

Management Agency (FEMA) guidelines, the plan should include the following: 

•	 Concept of operations 

•	 Coordinated response, responsibilities, and liaisons among different departments 

and agencies 

•	 Sequence of events that should occur for an effective response 

•	 List of potential areas of vulnerability 

•	 Procedures for notification and activation of crisis management teams 

•	 Establishment of a mobile command center with essential communications 

equipment 

•	 Designated radio frequencies for emergency communications 

•	 Procedures for dealing with bomb threats and suspicious objects 

•	 Evacuation and shutdown procedures 

•	 Identification of emergency evacuation routes and staging areas for response teams 

•	 Measures ensuring safety and security after an incident 

•	 Procedures for restoring service and establishing alternate routes 

•	 Removal plan for damaged equipment and structural elements 

•	 Procedures for issuing information and reassuring the public 

•	 Procedures for dealing with victims and notification of relatives 

•	 Regular updates based on events that identify vulnerabilities in the plan 

•	 Communication and coordination with local, state, and federal law enforcement 

agencies to obtain terrorism intelligence, training, and technical support 

29 These countermeasure options are from Design of Bridges for Security: NCHRP Bridge Infrastructure Vulnerability Assessment Workshop, 

presented by Capt. David Winget, University of Texas Department of Civil Engineering, February 10, 2003. 

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•	 Regular drills, tabletop exercises, no-notice responses, and full-scale simulations 

aimed at specific objectives to identify problem areas and test response procedures, 

communication, and coordination 

•	 Plans for rapid debris removal and repairs 

•	 Development of a training plan for maintenance personnel (observant of surroundings 

and knowing how to deal with suspicious objects) 

•	 Establishment of a security policy 

Information control measures 

•	 Review and sanitize websites for potential information that may be beneficial to 

terrorists. However, removal of data from websites must be balanced with the need 

for information sharing. For example, information about a specific bridge can be 

very useful for identifying weaknesses and planning an attack, but general design 

guidelines and “standard” plans generally provide information that is not directly 

beneficial to terrorists. 

•	 Establish a common classification system for sensitive information. Implement procedures for the control of sensitive information, including document classification, 

disposal of sensitive materials, and tracking the distribution of design information 

to contract tenderers. Establish “need-to-know basis” procedures for the release 

of vulnerabilities, security measures, emergency response plans, or structural details 

for specific bridges. 

Site layout measures 

•	 Improved lighting with emergency backup (combined with elimination of hiding 

spaces below) 

•	 Clearing overgrown vegetation to improve lines of sight to critical areas 

•	 Creative landscaping with regular maintenance to increase standoff distance to 

critical areas 

•	 Elimination of access to critical areas (beneath deck, maintenance rooms with 

access to cables, etc.) 

•	 Elimination of parking spaces beneath bridges 

•	 Providing pass-through gates in concrete median barriers to enable rerouting 

of traffic and access for emergency vehicles 

•	 Review of locations of trashcans or other storage areas that could be used to 

conceal an explosive device, ensure they are not near critical areas 

Access control/deterrent measures 

•	 Police patrol and surveillance 

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•	 Guards 

•	 Enhanced visibility 

•	 Signs issuing warnings that property is secured and being monitored 

•	 Marked vehicles 

•	 Keyless entry systems 

•	 Exterior and interior intrusion detection systems 

•	 Boundary penetration sensors (below bridge) 

•	 Volumetric motion sensors (for towers, maintenance buildings, inside box girders, etc.) 

•	 Point sensors (critical connections) 

•	 CCTV placed where it cannot be easily damaged or avoided while providing coverage 

of critical areas (to monitor activity, detect suspicious actions, and identify suspects) 

•	 Incorporation of a higher level of identification procedures and credentials for 

maintenance personnel, security personnel, and external contractors 

•	 Denied/limited access to critical structural elements (i.e., providing fencing around 

cable anchors, restricting access to box girders and cable towers, etc.) 

•	 Denied/limited access to inspection platforms 

•	 Physical barriers to protect piers 

•	 Physical barriers to control access to the deck during credible threats to a specific 

bridge (used in conjunction with random vehicle searches) 

•	 Rapid removal of abandoned vehicles 

•	 No fly zones around critical bridges 

•	 Emergency telephones to report incidents or suspicious activity 

•	 Use of an advanced warning system, including warning signs, lights, horns, and 

pop-up barricades to restrict access after span failure (manually activated or activated 

by span failure detectors) 

Retrofit Options 

•	 Reinforcing welds and bolted connections to ensure that members reach their full 

plastic capacity (designed for 120% of connected member capacity to account for 

strength increases during high-rate straining) 

•	 Using energy absorbing bolts to strengthen connections and reduce deformations 

•	 Adding stiffeners and strengthening lateral bracing on steel members to prevent 

local buckling before they reach their full plastic capacity 

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•	 Designing portions of the deck to “blow out” and create a vent to reduce pressures 

on the support structure (possibly near the abutments where large pressures build 

up from confinement effects) 

•	 Adding Carbon Fiber Reinforced Polymer (CFRP) hoop wraps on concrete 

columns, which can be reinforced with longitudinal wraps, to enhance concrete confinement, increase bending resistance and ductility, and add protection against 

spalling (can also be used on bents and beams) 

•	 Strengthening the lower portions (or full height) of columns against impacts and 

localized blast damage by encircling them with a steel casing (connected with high 

strength bolts and epoxy or a layer of grout) 

•	 Adding lateral bracing to columns to allow them to develop plastic hinges while 

preventing buckling 

•	 Adding 360-degree pier protection for impacts and standoff distance — possible 

alternatives include concrete barriers, stationary fender systems, dolphins, rotational 

bumper systems, or elastomeric energy absorbers 

•	 Restraining sections of the bridge with steel cables to reduce the chance of deck 

collapse at the supports, including cable supports to keep the deck from separating 

at the joints and hinge restrainers to hold the deck to the columns (can also be 

accomplished with high-strength threaded rod restrainers and pipe seat extenders) 

•	 Increasing the size of abutment seats and adding hinge seat extensions under 

expansion joints to reduce the chance of deck collapse at the supports 

•	 Increasing footing size (possibly combined with adding additional pilings in the 

ground or using steel tie-down rods to better anchor the footings to the ground) 

to improve resistance to cratering and large column deformations 

•	 Wrapping the lower portions of cables on cable-stayed bridges and suspension 

bridges with CFRP or other types of protective armor to protect against damage 

from blast and fragmentation 

•	 Increasing standoff distance and reducing access to critical elements with structural 

modifications (extending cable guide pipe length, moving guard rails, etc.) 

•	 Including reinforcing steel on top and bottom faces of girders to increase resistance 

to uplift forces from blasts that are in the opposite direction from those due to 

gravity and live loads 

•	 Providing system redundancy to ensure alternate load paths exist (through continuity, 

strengthening of connections, redundancy in cables and girders, etc.) should a critical 

structural element fail or become heavily damaged as a result of a terrorist attack 

•	 Strengthening the deck on curved steel trapezoidal girder bridges to ensure that sufficient torsional strength is provided should a portion of the deck be compromised 

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Threat Level Based Measures 

Threat 

Level to Bridges 

Additional Security Measures 

(“High Priority” – bridges that score a high R) 

Severe • 

• 

Restrict access with guards, barriers, and vehicle searches 

All other measures listed below 

High 

• 

• 

• 

• 

• 

Increase frequency of patrols and checks 

Conduct unscheduled exercise of emergency response plan 

Postpone non-essential maintenance 

Coordinate with National Guard or law enforcement for possible 

closure and vehicle searches when severe level is reached 

All other measures listed below 

Elevated • 

• 

Implement regularly scheduled police patrols 

All other measures listed below 

Guarded • 

• 

• 

Review and update emergency response procedures 

Increase frequency of periodic checks of cameras, fences, etc. 

All other measures listed below 

Low 

• 

• 

• 

• 

• 

Monitor security systems in place (including periodic checks) 

Disseminate threat information to personnel 

Regularly refine and exercise emergency operations plan 

Conduct emergency responder training 

Continually update threat and vulnerability assessments 

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Appendix B: Operational Security Practices 

This list of Operational Security Practices was developed during the AASHTO/FHWA BRP 

initial meeting to ensure that the panel considered the full range of security strategies. 

Following the initial meeting, the panel focused more narrowly on the design and engineering 

considerations contained in the body of this report. 

Management and Operational Practices 

•	 Best Practices. Current and timely exchange of practical information among 

owners and operators concerning the potential for and counters to terrorist 

attacks and related matters 

•	 Practice Review. Process for reviewing overall security management practices, 

including personnel policies, training, procedures, and use of technology 

•	 Institutional Relationships. Clarification and/or establishment of roles and 

responsibilities among federal, state, and local entities and effective partnerships 

for preventing, defeating, and responding to terrorists’ attacks 

•	 Preparedness. Guidance to owners/operators regarding preparations for 

responding to terrorists’ attacks, including coordination with other federal, state, 

and local agencies, communication protocols, and equipment interoperability 

•	 Personnel and Vehicle Security. Guidance to operators for ensuring that 

employees, contractors, vendors, visitors, and the vehicles they operate are 

authorized, verified, and authenticated, as appropriate 

•	 Communication/Outreach. Communication strategies for community outreach 

and coordination of sensitive information (e.g., with other agencies, media, private 

sector entities) 

Information Security 

•	 Procurement Practices. Means for procuring security-sensitive technologies without public disclosure and for soliciting construction bids without disclosing securitysensitive design features 

•	 Information Security. Means for controlling public access to “as built” drawings 

and related information 

Mobilization (“notice”) and Response (“trans-event”) 

•	 Threat Warning. Means (protocols) for timely notification of owners/operators 

concerning imminent threats to specific assets 

•	 Early Response. Policies and processes for interdicting identified threats, 

informing/instructing travelers, and evacuating facilities 

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•	 Initial Response. Policies, process, and technologies needed to execute the preparedness plan in response to terrorists’ attacks 

Recovery (Post-event) 

•	 Damage Assessment. Procedures and technologies that assist in initial assessment 

of structural damage to the asset to determine the effect of the attack on functionality 

(e.g., closure, restricted use) 

•	 Functional Continuity. Contingency plans for reestablishing asset functionality 

(including use of available alternatives, emergency repairs) 

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Appendix C: Case Study in Bridge and Tunnel 

Risk Assessment 

Risk Assessment Approach 

This appendix describes the risk assessment method used to help determine how to allocate resources for mitigating the adverse effects of terrorist acts on critical transportation 

facilities and the occupants of those facilities. Decisions on how best to spend mitigation 

funds require a rational and systematic risk-based approach that considers, for each facility, 

the combination of hazard occurrence likelihood, consequences given the occurrence, and 

socioeconomic importance of the facility. Risk assessment methods for mitigation decisions 

related to natural hazards are fairly well established. The application of these methods to 

non-natural hazards (i.e., acts of terrorism) is relatively new. There is no well-established 

comprehensive procedure that can be used to determine how terrorism mitigation funds 

should be spent given a finite list of facilities, mitigation alternatives, and agency-defined 

constraints. 

We used a rational and systematic risk assessment method for prioritizing alternatives for 

mitigating the effects of acts of terrorism. The method makes use of several key sources of 

information, including the following: 

•	 Prior work in seismic risk assessment for retrofit prioritization (Maroney, 1990; Sheng 

and Gilbert, 1991; Kim, 1993; Babaei and Hawkins, 1993; Hart Consultant Group et al., 

1994; King and Kiremidjian, 1994; Basoz and Kiremidjian, 1995; Audigier et al., 2000) 

•	 DOD procedures for addressing physical threats in facility planning (U.S. Department 

of Defense, 1994) 

•	 AASHTO Guidelines for highway vulnerability assessment (AASHTO, 2002) 

•	 U.S. Department of Justice state preparedness support program (U.S. Department of 

Justice, 2000) 

•	 Analytic Hierarchy Process for consensus decision making given multiple attributes 

(Saaty, 1980) 

The risk to a facility due to a man-made hazard is represented as the combination of the 

following three factors as shown in Figure C-1: 

•	 Importance Factor (IF).A measure of the socioeconomic impact of the facility’s 

operation, computed as a weighted combination of the following attributes of the facility: 

– Historical and symbolic importance 

– Replacement value 

– Importance as an emergency evacuation route 

– Importance to the regional economy 

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– Importance to the regional transportation network 

– Annual revenue value
 

– Criticality of the utilities attached to the facility
 

– Military importance
 

– Exposed population on or in the facility 

•	 Occurrence Factor (OFi). A measure of the relative probability or likelihood of 

threat i occurring, computed as a weighted combination of the following: 

– Level of access 


– Level of security 


– Visibility or attractiveness of the facility 


– Level of publicity 


– Number of times the facility has been threatened in the past
 

•	 Vulnerability Factor (VFi). A measure of the consequences to the facility and the 

occupants given the occurrence of threat i, computed as a weighted combination of 

the following: 

– Expected damage to the asset 

– Expected down-time or closure of the facility 

– Expected number of casualties 

Expressed in equation format, the risk score (RS) for a given facility, is written as follows: 

RS = IF x ∑ [OFi x VFi ] (1) 

where OFi,VFi, and IF are defined as above, and ∑ denotes the summation over all 

considered threats to the facility. 

Each of the factors in Equation (1) is a number between 0 and 1, computed using a multivariate utility method. In this method, each factor is computed as the summation of the 

weighted values (between 0 and 1) of the attributes that define the factor as follows: 

IF = ∑ [Wj x Vj(Xj)] (2a) 

OF = ∑ [Wj x Vj

(Xj)] (2b) 

VF = ∑ [Wj x Vj

(Xj)] (2c) 

where xj is the value of attribute j (e.g., very high), vj(xj) is the function or table that maps 

xj to a utility value (between 0 and 1; e.g., very high corresponds to 1), wj is the weighting 

factor on attribute j, and ∑ denotes the summation over all considered attributes for the 

factor. See Figure C-1 for a graphical depiction of the above discussion. 

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The weighting factors used for combining the attributes that make up each of the factors 

listed above are developed using the pair-wise comparison procedure in the Analytic 

Hierarchy Process, whereby each member of the decision making group assigns a numerical 

value to the relative influence of one attribute over another. The scores are averaged and 

used to compute the weighting factors, which are then reviewed by the group as a whole 

and revised until all members of the group are satisfied with the results. Figures C-2 

through C-4 show the relative weights for the attributes used to compute the Importance 

Factor, Occurrence Factor, and Vulnerability Factor, respectively. 

After the weighting factors have been developed, the risk assessment method proceeds as 

follows for each facility: 

1.	 Compute the Importance Factor (Equation (2a)) by assigning values to the attributes 

that contribute to the factor 

2.	 Identify vulnerable components of the facility 

3.	 Identify credible threats to each component 

4.	 Compute the Occurrence Factor (Equation (2b)) and Vulnerability Factor (Equation (2c)) 

for each threat by assigning values to the attributes that contribute to the two factors 

5.	 Compute the baseline Risk Score (Equation (1)) for the facility as a combination of the 

Importance, Occurrence, and Vulnerability Factors as shown in Figure C-1 

6.	 Identify the mitigation projects for the facility and the threats that will be mitigated 

7.	 For each mitigation project, re-compute the Occurrence and Vulnerability Factors 

(Equations (2b) and (2c)) given the presence of the mitigation project, and then recompute the Risk Score (Equation (1)) 

8.	 Rank the mitigation projects in terms of reduction in Risk Score compared to the 

baseline Risk Score for the facility computed in Step 5 

Risk Assessment Results 

The result of this risk assessment effort is a ranked list that identifies the benefit of enacting each mitigation project. The costs (in terms of capital expenditure, operation and maintenance, and disruption) were developed in a parallel effort and used with these results in 

an explicit cost-benefit analysis to identify the final list of mitigation projects to pursue. 

Prior to developing the final ranked list of projects based on the cost-benefit comparison, 

several intermediate results were examined to ensure that the final results would be both 

rational and practical. For example, Figure C-5 shows the ranking of the eight facilities by 

Importance Factor. Figures C-6 through C-11 show the breakdown of each facility into the 

vulnerable components or threat targets. 

The final list of mitigation projects, ranked by the ratio of benefit (in terms of reduction in 

facility Risk Score) to project cost, is given in Table C-1. 

45 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Figure C-12 shows the resulting ranked list in a chart format to help illustrate the comparison of mitigation project benefits and costs. 

Risk Assessment References 

AASHTO, 2002, A Guide to Highway Vulnerability Assessment for Critical Asset Identification and 

Protection, Prepared by SAIC, Washington, DC. 

Audigier, M.A., Kiremidjian, A.S., Chiu, S.S., and King, S.A., 2000, “Risk Analysis of Port 

Facilities,” Proceedings of the 12th World Conference on Earthquake Engineering, paper no. 

2311. 

Babaei, K., and Hawkins, N., 1993, Bridge Seismic Retrofit Planning Program, Report WA-RD 

217.1, Washington State Department of Transportation, Olympia, WA. 

Basoz, N., and Kiremidjian, A.S., 1995, Prioritization of Bridges for Seismic Retrofitting, Report 

No. 114, John Blume Earthquake Engineering Center, Department of Civil Engineering, 

Stanford University, Stanford, CA. 

Hart Consultant Group et al., 1994, Seismic Risk Decision Analysis for Kaiser Permanente 

Pasadena, Final Project Report, Santa Monica, CA. 

Kim, S.H., 1993, A GIS-Based Risk Analysis Approach for Bridges Against Natural Hazards, Ph.D. 

Dissertation, Department of Civil Engineering, State University of New York, Buffalo, 

NY. 

King, S.A., and Kiremidjian, A.S., 1994, Regional Seismic Hazard and Risk Analysis Through 

Geographic Information Systems, Report No. 111, John Blume Earthquake Engineering 

Center, Department of Civil Engineering, Stanford University, Stanford, CA. 

Maroney, B., 1990, CALTRANS Seismic Risk Algorithm for Bridge Structures, Division of Structures, 

California Department of Transportation, Sacramento, CA. 

Saaty, T.L., 1980, The Analytic Hierarchy Process, McGraw-Hill, New York, NY. 

Sheng, L.H., and Gilbert, A., 1991, “California Department of Transportation Seismic Retrofit 

Program: The Prioritization and Screening Process,” Proceedings of the Third U.S. National 

Conference on Lifeline Earthquake Engineering, pp. 1110-1119. 

U.S. Department of Defense, 1994, TM 5-853/AFMAN 32-1071,Volume 1, Chapter 3, 

Planning Phase, Washington, DC. 

U.S. Department of Justice, 2000, Fiscal Year 1999 State Domestic Preparedness Support 

Program, Washington, DC. 

46 
Importance 

Factor (IF) 

Occurance 

Factor (OFi

) 

Vulnerability 

Factor (VFi

) 

Facility Risk Score (RS) 

• Historical/symbolic 

• Replacement value 

• Evacuation route 

• Regional economy 

• Transportation network 

• Annual revenue 

• Attached utilities 

• Military route 

• Exposed population 

Importance Attributes Weighting Orrurence Attributes Weighting 

• Access for attack 

• Security against attack 

• Visibility as a target 

• Publicity if attacked 

• Past threats/attacks 

Weighting 

factors for factors for 

Vulnerability Attributes 

• Expected damage 

• Expected closure 

• Expected casualties 

factors for 

combining combining combining 

attributes attributes attributes 

Decisionmaker Security Decisionmaker Engineering 

consensus information consensus Analysis 

Decisionmaker 

consensus 

Historical significance 

Importance as an evacuation 

Importance to the regional economy 

Importance to the transportation network 

Replacement value 

Revenue value 

Criticality of attached utilities 

Military importance 

Level of exposed population 

Figure C-2. Relative Weights for Attributes Used to Compute Importance Factor 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Figure C-1. Components in Risk Assessment for an Individual Facility 

47 
Access for attack (AA) 

Level of security (LS) 

Visibility or attractiveness as a target (VT) 

Level of publicity if attacked (PL) 

Number of past threats (PT) 

Figure C-3. Relative Weights for Attributes Used to Compute Occurrence Factor 

Expected damage (ED) 

Expected downtime (DT) 

Expected number of casualties (CR) 

Figure C-4. Relative Weights for Attributes Used to Compute Vulnerability Factor 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

48 
1 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

Bridge 1 Tunnel 1 Tunnel 2 Other 

Facility 1 

Bridge 2 Bridge 3 Bridge 4 Other 

Facility 2 

Figure C-5. Ranking of Facilities by Importance Factor 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

49 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

BRIDGE 1 

Main Pier Base A 

Pedestrian Water Borne Land Borne 

Pedestrian Water Borne Land Borne 

Main Pier Base B 

Top-End Pedestrian Vehicle Bottom-End Pedestrian 

Tension Hangers 

Pedestrian Vehicle 

Deck Level at Piers 

Pedestrian Vehicle 

Anchor Element A 

Pedestrian Vehicle 

Anchor Element B 

Pedestrian Vehicle 

Main Tension Member 

Pedestrian Vehicle 

Approach Highway 

Figure C-6. Breakdown of Bridge 1 into Vulnerable Components and Mode of Access 

50 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

TUNNEL 1 

Pedestrian Land Borne Water Borne 

B River Vent – Building 

Pedestrian Vehicle 

Plaza 

Pedestrian Vehicle 

Tunnel Structure 

Pedestrian Vehicle 

Mid-River Pump Chamber 

Pedestrian Vehicle 

A Land Vent – Building 

Pedestrian Vehicle 

C Land Vent – Building 

Pedestrian Vehicle 

D Land Vent – Building 

Pedestrian Vehicle 

Administration Building 

Pedestrian Vehicle 

Approach Viaduct 

Pedestrian Vehicle 

Approach Plaza 

Pedestrian Vehicle 

A Land Vent – Tunnel Ceiling 

Pedestrian Vehicle 

B River Vent – Tunnel Ceiling 

Pedestrian Vehicle 

C Land Vent – Tunnel Ceiling 

Pedestrian Vehicle 

D Land Vent – Tunnel Ceiling 

Figure C-7. Breakdown of Tunnel 1 into Vulnerable Components and Mode of Access 

51
 
BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

TUNNEL 2 

Pedestrian Vehicle Water 

B Vent River – Building 

Pedestrian Vehicle 

Portals 

Pedestrian Vehicle 

Tunnel Structure 

Pedestrian Vehicle 

Mid-River Pump Chamber 

Pedestrian Vehicle 

A Vent Land – Building 

Pedestrian Vehicle 

C Vent Land – Building 

Pedestrian Vehicle 

A Vent Land – Tunnel Ceiling 

Pedestrian Vehicle 

B Vent River – Tunnel Ceiling 

Pedestrian Vehicle 

C Vent Land – Tunnel Ceiling 

Pedestrian Vehicle 

D Vent River – Tunnel Ceiling 

Pedestrian Vehicle Water 

D Vent River – Building 

Figure C-8. Breakdown of Tunnel 2 into Vulnerable Components and Mode of Access 

52
 
BRIDGE 2 

Approach 

Piers 

Main Piers Main Span 

Pedestrian Vehicle Pedestrian Water 

Borne 

Pedestrian Vehicle 

Figure C-9. Breakdown of Bridge 2 into Vulnerable Components and Mode of Access 

BRIDGE 3 

Approach 

Piers 

Pedestrian Vehicle 

Main Piers 

Pedestrian Water 

Main Span 

Pedestrian Vehicle 

Figure C-10. Breakdown of Bridge 3 into Vulnerable Components and Mode of Access 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

BRIDGE 4 

Pedestrian Vehicle 

Approach 

Piers 

Pedestrian Water 

Main-Span 

Abutment 

Vehicle Pedestrian Vehicle 

Compression 

Members 

Pedestrian Vehicle 

Tension 

Hangers 

Figure C-11. Breakdown of Bridge 4 into Vulnerable Components and Mode of Access 

53 
5

10

15

20

25

30

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

Rank Facility Location Reduction in 

Risk Score 

Project Cost 

(x$1,000) 

1 Bridge 1 Main Pier Base B 0.16 753 

2 Other Facility 1 Element A 0.30 1,872 

3 Tunnel 1 Vent Buildings – Buildings 0.48 7,857 

4 Other Facility 1 Element B 0.34 8,243 

Bridge 1 Anchor Element B 0.11 2,840 

6 Bridge 1 Anchor Element A 0.10 2,840 

7 Other Facility 1 Element C 0.23 6,982 

8 Tunnel 1 Approach Viaduct 0.12 3,891 

9 Bridge 1 Main Pier Base A 0.32 13,937 

Bridge 4 Tension Hangers 0.05 2,944 

11 Tunnel 1 Vent Buildings – Tunnel 

Ceilings 

0.16 12,619 

12 Tunnel 1 Approach Plaza 0.03 2,787 

13 Tunnel 2 Vent Buildings – Buildings 0.10 9,142 

14 Tunnel 2 Vent Buildings – Tunnel 

Ceilings 

0.13 12,523 

Bridge 1 Deck Level 0.30 30,869 

16 Bridge 2 Main Piers 0.10 12,048 

17 Other Facility 1 Element D 0.05 7,432 

18 Tunnel 1 Administration Building 0.01 434 

19 Bridge 1 Tension Hangers 0.07 12,363 

Bridge 1 Approach Highway 0.15 32,686 

21 Other Facility 2 Element A 0.01 1,950 

22 Bridge 4 Main-Span Abutment 0.02 5,891 

23 Bridge 3 Main Piers 0.09 24,649 

24 Other Facility 1 Element E 0.10 31,754 

Other Facility 2 Element B 0.02 6,896 

26 Tunnel 1 Tunnel Structure 0.51 222,723 

27 Tunnel 2 Tunnel Structure 0.35 186,735 

28 Other Facility 1 Element F 0.03 20,516 

29 Bridge 4 Compression Members 0.01 8,687 

Bridge 2 Main Span 0.08 64,996 

31 Bridge 3 Main Span 0.07 108,718 

32 Tunnel 1 Portals 0.01 16,040 

33 Tunnel 2 Portals 0.01 14,287 

Table C-1. Final Ranking of Mitigation Projects by Benefit/Cost Ratio 

54 
Benefit/Cost Comparison by Project Rank 

Reduction in Risk Score 

1 

0.1 

0.01 

1 

2 

3 

4 9 15 

8 

5&6 

10 17 

12 

2225 

29 

28 

13 

11 

23 24 

20 

21 32 

33 

31 

30 

27 

26 

18 

7 

Bridge 1 

Tunnel 1 

Tunnel 2 

Other Facility 1 

Bridge 2 

Bridge 3 

Bridge 4 

Other Facility 2 

16 

14 

Beneficial but 

higher cost 

projects 

Least desirable 

projects – higher 

cost/lower 

benefit 

Less costly but 

lower benefit 

projects 

Most desirable 

projects – 

higher benefit/ 

lower cost 

$1,000,000 $10,000,000 $100,000,000 

19 

0.001 

$100,000 $1,000,000,000 

Figure C-12. Chart Illustrating Comparison of Benefits and Costs for All Mitigation Projects 

Project Cost 

BLUE RIBBON PANEL ON BRIDGE AND TUNNEL SECURITY 

55 


FHWA-IF-03-036
 

HIBT/10-03 (3M)E