U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000


Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration

Bridges & Structures

<< Previous Contents Next >>

Recommendations for 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 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]

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.

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.

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


[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 5percent 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.

[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.

[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.

<< Previous Contents Next >>
Updated: 06/25/2013
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000