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Recommendations for Bridge and Tunnel Security

Section 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. Sub-section 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.
  • 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 mid-term 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.

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.
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 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 "design-for-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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Updated: 06/25/2013
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