Bridge Security Guidelines
|Publication Date:||1 January 2011|
An assessment of the importance of a specific bridge should be conducted during the planning of new bridges, rehabilitation of existing bridges, or both.
For bridges deemed important, a formal vulnerability study should be conducted and measures to mitigate the vulnerabilities should be incorporated in the design.
This article presents a broad view of the issues that need to be considered during the planning and design of bridge projects to address bridge security. Bridge owners should establish criteria for the size and location of the threats to be considered when analyzing bridges for security as specified in Article 1.2. These criteria should take into account the type, geometry, and importance of the structure being considered.
Bridge owners are responsible for establishing the procedures by which bridge importance is assessed and by which formal vulnerability studies are conducted. This work can be carried out by bridge owners with appropriate experience or by retaining the services of a qualified security consultant.
Currently, there are no uniform procedures for assessing the importance of a bridge. Accordingly, it is up to the discretion of the bridge owner to establish the procedures required to assess the importance of a bridge. Factors common to many of the proposed procedures include the following:
• Social and economic impact of bridge loss,
• Role played by bridge in defense or security of region, state, and nation,
• Average daily traffic,
• Average daily truck traffic,
• Distance to nearest detour, and
• Symbolic importance.
Work is being done to produce a uniform procedure to prioritize bridges for security. In the absence of uniform procedures, some states have developed their own, incorporating security prioritization methods that, while similar, differ in the details. In addition, state procedures to assess bridge importance have been developed by departments of transportation to assist in prioritizing seismic rehabilitation. These procedures also may be used in conjunction with security considerations.
Guidance on security strategies and risk reduction may be found in the following documents: Design of Critical Bridges for Security against Terrorist Attacks (27), A Guide to Highway Vulnerability Assessment for Critical Asset Identification and Protection (21), Improving Surface Transportation Security: A Research and Development Strategy (10), Protecting Public Surface Transportation against Terrorism and Serious Crime: An Executive Overview (15), and Recommendations for Bridge and Tunnel Security (7), as well as in the ASCE Journal of Bridge Engineering articles "Analysis and Design of Critical Bridges Subjected to Blast Loads" (26), "Risk-based Prioritization of Terrorist Threat Mitigation Measures on Bridges" (17), and "Risk Management and Design of Critical Bridges for Terrorist Attacks" (25).
Though not specific to bridges, the Federal Emergency Management Agency (FEMA) has published a series of reports that provides valuable information on risk management to mitigate potential terrorist attacks, including FEMA 426 (12) and FEMA 452 (13). Unified Facilities Criteria (UFC) 4-020-01, a publically available U.S. Department of Defense publication (32) addressing facilities planning, also has guidance that may be relevant for bridges.