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Recommendations for Bridge and Tunnel Security

Appendix A: Countermeasure Options[29]

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
  • 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
  • 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
  • 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

Threat Level Based Measures

Threat Level to Bridges Additional Security Measures ("High Priority" - bridges that score a high R)
  • Restrict access with guards, barriers, and vehicle searches
  • All other measures listed below
  • 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
  • Implement regularly scheduled police patrols
  • All other measures listed below
  • Review and update emergency response procedures
  • Increase frequency of periodic checks of cameras, fences, etc.
  • All other measures listed below
  • 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

[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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Updated: 06/25/2013
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