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2 1.1 Audience Target/Asset--Persons, facilities, activities, or physical systems that have value to the owner or to society as a The anticipated audience for these guidelines includes the whole. following: Damage Potential--The potential for negative effects-- including immediate and long-term damage or loss, Tunnel authorities or asset owners, whether tangible or intangible--resulting from an unin- State and local transportation departments and agencies tentional event or an attack on an asset. Mission-related responsible for tunnel operation and maintenance, damage potential (i.e., impacts that are critical to the Enforcement personnel and first responders responsible owner's transportation institutional mission, including for tunnel safety and security, and destruction or damage causing loss or reduction of func- Tunnel design consultants. tionality) is of special importance, together with injury or loss of life, as well as impacts on quality of life and morale. Damage potential grows as a function of an asset's critical- 1.2 Basic Definitions ity. However, a critical asset may be damaged without a The basic concepts of risk management involve the rela- total loss of functionality. tionships among (a) the nature of the threat or hazard that Vulnerability--A weakness in asset design or operations can cause damage to a susceptible asset, (b) the asset's opera- that can be exploited by a threat or hazard to produce neg- tional and physical vulnerabilities to attack and/or failure, ative consequences, or damage. Specific threats and haz- and (c) the damage potential (consisting of the loss of use of ards therefore relate to different vulnerabilities. that asset and the loss of benefit of that asset to users). Understanding relevant terminology is critical for all-hazards It should be noted that the specific quantitative relation- risk management and countermeasure strategy development. ship among the variables in the risk equation depends on Most important is the distinction between hazards, which are how the various factors are developed and expressed. For unintentional, and threats, which are intentional. Neither of example, damage potential and vulnerability of assets can be these terms implies a probability or likelihood that the event will judged on a relative scale with upper and lower bounds or materialize unless the terms are modified with explicit proba- through analytical models that assess asset criticality in bility descriptors. The following definitions are used in this terms of potential casualties, economic impacts, or physical report: or operational vulnerabilities. However, the probability of a threat or hazard materializing to trigger the consequences Hazard--The potential unintentional condition or event may be difficult to estimate in more than qualitative or capable of disrupting or negatively impacting an asset, relative terms. such as fire, power loss, or equipment breakdown. Hazards are usually associated with natural events and safety and 1.3 Methodology are often measured in terms of the frequency and magni- tude of the event. Hazards can also include degradation of Vulnerability and damage potential have been ranked on structural integrity. relative scales and analyzed to develop priorities for counter- Threat--The potential intentional act capable of disrupt- measures. ing or negatively impacting an asset. In other words, threats are deliberate attempts of a person or group to achieve var- 1.4 Assumptions ious criminal or terrorist ends that may involve loss of life, loss of function, loss of visibility, and other objectives. This report was prepared using the collective knowledge Threats are distinct from hazards because they are not and experience of the authors. Common sense was used to acts of nature, accidents, or organic happenstances for avoid unnecessary duplication of effort; further exploration which tunnels are normally designed. Rather, threats are of common topics encountered by a tunnel owner or opera- typically characterized as acts of intrusion; placement of tor; and improbable hazard and threat situations, damage explosive devices; and/or chemical, biological, or radiolog- potential, and countermeasures. ical attacks. In the case of terrorism, a threat consists of a The single most significant assumption made during this scenario that combines a weapon, a host (i.e., an aggres- research effort is that guidelines that cover the range of "rou- sor), a delivery mode, and tactics (i.e., a path of approach, tine" hazards to tunnel safety--such as equipment break- the use of stealth or force, and the actual target of weapon downs, derailments, utility disruptions, minor criminal acts, placement). While hazards are associated with safety, and medical emergencies--already exist. The experience of threats are associated with security. tunnel operators in handling these minor incidents is already

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3 addressed in handbooks, manuals, and industry standards that Additional assumptions include the following: are readily available. Wherever possible, references to these materials are noted in the text. The addition of security-related The physical aspects of the tunnel (i.e., structural aspects, threats--from both major criminal acts and terrorism--then geotechnical aspects, and water levels) are known before becomes an important extension to an "all-hazards" approach the tunnel owner or operator uses this guide. to tunnel security. Before implementing any of the countermeasures recom- The research did not address nuclear threats, common mended herein, the tunnel owner or operator will conduct a natural or weather hazards, or inspection or maintenance full engineering assessment that takes into account facility- issues. specific conditions.