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6 the MS Excel modeling and presentation features are prepro- 1. Identify and select the appropriate state-level TCP data- grammed for the requirements of this project. The MS Excel bases containing relevant data on mountain passes, tun- part of DIETT is structured to calculate the transportation- nels, and bridges. related and the economic-related impacts (costs) and to facil- 2. Select the specified datasets (e.g., identifiers, bridge span, itate the development of alternate scenarios. Automatic sort detour length, and number of vehicles). functions were added to allow for ease of prioritization. 3. Direct the database (an automated function) to select the top TCP candidates (500 is the suggested number of candidates) The optional programs fine-tune the prioritizations based on preprogrammed initial selection criteria. This list developed in DIETT. One suggested program is ArcGIS will be automatically exported to the MS Excel spreadsheet. (version 9.0), designed to identify detours based on a geo- 4. Further prioritize the list in MS Excel by changing trans- graphic information system (GIS). These data can replace the portation cost, performance, and economic impact default detour lengths specified in other sources, such as the National values (these are automated functions). Bridge Inventory (NBI). Other programs may be applied by 5. Refine the output (optional, but highly recommended) the users, as deemed appropriate. using more specific state transportation and commerce data It is recommended that DIETT reside in a consequence and other programs. The number of TCPs to be refined and management package called the Consequences Assessment the extent of the refinements are determined by the Tool Set--Joint Assessment of Catastrophic Events (CATS- user's needs, the availability of data, and the desired level JACE), which is based on a commercial geographic informa- of accuracy. tion system (GIS). CATS-JACE is a configuration of CATS, a disaster analysis system, which is available as an off-the-shelf 6. Create an output file. Save or print. package. CATS-JACE was developed for the Federal Emergency 7. Compare results with state-level lists of important TCPs to Management Agency (FEMA) and the Defense Threat Reduc- make sure that high-value TCPs were not systematically tion Agency (DTRA) to provide a comprehensive package of eliminated. (See "Limitations.") hazard prediction models (natural hazards and technologi- More detailed installation and operating instructions are cal hazards) and casualty and damage assessment tools. provided in Part 2 of this volume, "DIETT Installation CATS-JACE has the capability to overlay event characteris- Instructions and User Guide." For security reasons, data used tics (e.g., dispersion paths), transportation (e.g., rail and high- way networks), population, and business datasets to provide an to illustrate the use of DIETT were altered NBI data from dif- understanding of the extent, magnitude, duration, and impacts ferent U.S. states entered as the data of an imaginary state-- of an event. CATS-JACE also accepts real-time data from local Fredonia. meteorological stations. It is recommended that DIETT reside in CATS-JACE 1.4 Limitations because CATS-JACE is available to many state transportation and security agencies and because it already contains ArcGIS DIETT has some inherent limitations; these are due to scope (version 9.0). When DIETT resides within CATS-JACE, it of work limitations and the generalizations in the algorithms. can interact with resident security-related programs. For Generally, the generalizations in the algorithms imply a greater more information on CATS, see the appendix to this report degree of uniformity and precision than really exists. Further or access the "Consequences Assessment Tool Set" at http:// limitations are introduced from external sources, predomi- As illustrated in Exhibit 1, the structure of DIETT is rela- tively simple. Exhibit 1 shows the structure, relationships, and Security Caution processes of DIETT and the four categories of state-level datasets suggested (mountain pass, tunnel, bridge, and state DIETT is an analytical tool that helps users to prioritize transportation and commerce). transportation choke points (1) by value to the U.S. transportation system and (2) by value to the national 1.3 Using DIETT economy. For security reasons, data used to illustrate the use of DIETT were altered. When the tool is used The output of DIETT is a list of state-level TCPs, prioritized with actual data, the results could not only help users by net national economic impact. The output is developed with legitimate purposes, but also those intending to through an interconnected, semi-automatic set of functions disrupt the U.S. transportation infrastructure. There- implemented by an analyst (who, ideally, will have at least a fore, DIETT outputs should be guarded, and access moderate level of knowledge of MS Access and MS Excel). The should be limited to those with a "need to know." general, sequential, steps are as follows:

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7 Exhibit 1. The structure and flow of the Disruption Impact Estimating Tool--Transportation (DIETT). nantly by the limitations of the data. Some key limitations adjust some relationships in the final refinement steps. under each of these categories are noted below: However, there may still be a large number of errors, which could result in premature exclusion of certain high- Inherent Limitations--these include but are not limited to value TCPs. The user should compare results with state- the following: level lists of important TCPs to make sure that high-value Considering only the commercial-shipment trans- TCPs were not eliminated. portation sector limits the scope of the transportation- Externally Introduced Limitations--the dominant exter- related impacts that will be reported. This limitation is nally introduced limitations are the data. Through limited pronounced for TCPs in which commercial traffic is spot validation for the state of Virginia, some critical data only a small fraction of the total traffic. (Note: the non- from the NBI were found to be suspect. These included commercial transportation sector was specifically excluded length of the detour, number of trucks, and global- in the scope.) positioning-system (GPS) position specifications. This Repair or replacement costs for TCPs are not sup- limitation suggests the importance of refining the output ported by the available data and were not included. In of DIETT. some cases, this cost element can be a large, or even the Other Limitations--DIETT may not adequately consider largest, component of total losses. the impact of multiple local or regional events. Similarly, it The difference between estimated default values and is not readily applicable to multiple events along a main actual values can be significant. Even though the user can transportation corridor. In some cases, such as the disable- narrow this difference by changing the default values ment of a bridge that carries truck and rail traffic, the through the final refinement steps, there may still be a large impacts may be more severe than indicated by the model. number of errors, which can result in premature exclusion The detour data provided in the NBI do not consider the of certain significant TCPs. The user should compare structural capacity of the road to carry the increased traffic. DIETT results with state-level lists of important TCPs to Validation--DIETT results were not validated. make sure that high-value TCPs were not eliminated. The relationships built into the formulas contain sim- Other limitations may apply to individual states and TCPs. plified estimates of observed or assumed relationships. The user should make application-specific assessment of The user may change the formulas, as appropriate, and DIETT and data limitations.