Intelligence since 2001 has dramatically changed the threat landscape for iconic bridges. Specific threats to bridges in New York and California have been uncovered by law enforcement. Suspected terrorists have been arrested with video footage of critical structural elements and information on cutting devices that could be used to attack bridge supporting cables.
A successful attack against a historically significant bridge would certainly result in loss of life, structural damage and significant immediate effects on the economy. The paralyzing impact of public fear coupled with the ongoing financial impacts from a prolonged disruption of commerce is almost incalculable. This is especially true if the restoration and reopening of the damaged structure takes an extended period of time, which would be the case for iconic structures.
The transportation community has always prepared for the impact of natural disaster; however, designing for and addressing these potentials do not adequately deal with the new challenges presented by a potential terrorist attack. Much research has been conducted to mitigate the effect of flooding, earthquakes and wind events on bridges. Many of the world’s elite structural engineers have spent thousands of hours contemplating and calculating the best ways to physically protect bridges of all types and sizes. What has not been documented to date is the role security technology plays in the deterrence, detection and assessment of attacks against these historical structures.
Physical Limitations of Historical Bridge Designs
Maintaining standoff distances to critical structural components and physical hardening of these structures are two obviously important elements considered by today’s bridge engineers. However, many iconic bridges were built long before today’s threat realities, stringent design standards and traffic planning requirements. Some of these bridges are more than a century old and the fact that they remain standing and able to convey vehicles of any kind is an engineering marvel. As a result, implementing some of the desired physical protective measures on these sensitive structures can be difficult or unfeasible.
In some cases, the sheer weight of proposed physical hardening measures is prohibitive from a structural perspective. In other cases, critical aesthetically significant components are located literally inches from active pedestrian walkways or vehicle roadways. Permanently closing lanes solely for the purpose of improving standoff distance is not a viable solution for heavily traveled thoroughfares. Designers therefore must take advantage of today’s security technology advances to bridge the gap between physical enhancement limitations and modern protective requirements.
Technology’s Emerging Role
Three important themes define technology’s emerging role in a comprehensive bridge security program. First, match the technology you deploy to the physical assessment and enhancements so that every piece of equipment supports the overall protection goals. Second, ensure that the technologies you choose will perform as necessary in the worst-case environment. Finally, ensure that technologies are symbiotic as opposed to cumulative in presenting responders with valid actionable information at all times.
Theme 1 — Match Technology to Real vs. Perceived Need: Logic tells us that detection should be moved to the furthest possible point away from critical assets to give responders a greater chance of successful intervention in the event of an adversarial attack. Unfortunately, the public has historically always had proximate access to bridge-critical assets by design. Therefore, even the most advanced and discriminating detection technologies cannot provide enough time or notice of undesired events necessary to prevent a successful attack against these assets.