|
Article Excerpt
The US Coast Guard (USCG) is charged with maintaining an acceptable level of safety in US ports and waterways. Allocating resources to solve safety problems is difficult because multiple attributes of a port or waterway affect its safety and determine whether a particular safety measure will improve it. We based the ports and waterways safety assessment (PAWSA) model on multiattribute decision analysis techniques and local experts' and stakeholders' assessments of safety levels and the effects safety alternatives would have on these levels. The USCG used the PAWSA model to justify funding for four new vessel traffic service centers and to determine new technology requirements for all commercial vessels using US waters. The USCG has adopted it as a permanent part of its safety management tool kit.
Key words: decision analysis: applications; transportation: safety and injuries.
History: This paper was refereed.
**********
During the early 1990s, the United States Coast Guard (USCG) invested in a project called VTS 2000. A vessel traffic service (VTS) is a traffic control center for ships using a particular port or waterway, similar to an air traffic control center. The USCG analyzed risk factors for 23 ports and determined that seven of them needed a VTS to reduce risk to an acceptable level. However, because the public had no role in the assessment process, people did not trust the results, and the politicians killed the project in the budgeting process. In the end, the USCG cancelled seven contracts for the new VTS.
In the 1997 Department of Transportation Appropriations Act, Congress directed the USCG "to identify minimum user requirements for new VTS systems in consultation with local officials, waterways users, and port authorities" and to review opportunities for private and public partnerships in VTS operations. The USCG asked maritime and port community stakeholders to identify the needs of waterway users with respect to ensuring the navigational safety in US ports and waterways. It formed a group to discuss such needs, whose members were drawn from the American Association of Port Authorities, the American Pilots' Association, the American Waterways Operators, the Council of American Master Mariners, Intertanko, the Passenger Vessel Association, the Natural Resources Defense Council, the US Chamber of Shipping, and the USCG.
Under the auspices of the Marine Board of the National Research Council, the group held four meetings between January and March 1997. The group conducted the national dialog to provide the foundation for developing an approach to the VTS that would meet the shared government, industry, and public objective of ensuring the safety of vessel traffic in US ports and waterways in a technologically sound and cost-effective way (USCG 2001). The participants agreed that the USCG and port users and stakeholders should take part in determining whether a VTS was needed in a particular port. Such collaborative analysis improves the decision-making process and increases the chances of implementing study recommendations (Busenberg 1999, 2000; Charnley 2000). Furthermore, the USCG should use defined criteria to conduct an initial screening and identify ports that might be candidates for a VTS. Each port's users and stakeholders should consider these criteria in detail and determine whether the port needs a VTS.
The vessel traffic management (VTM) technologies the national dialog group's participants endorsed were automatic identification systems (AISs) employing differential global positioning systems (DGPSs) and on-board transponders. A vessel's AIS emits its exact position from the DGPS. On-board equipment picks up the signals from all nearby, similarly equipped vessels and maps their positions, courses, headings, speeds, and identifiers. Augmented systems also provide weather forecasts, data on currents, and depth and emergency information. These enhanced automatic identification systems (EAIS) are full information systems for port users that do not depend on an on-shore facility with 24-hour staffing. The next level of VTM implementation is a vessel traffic information system (VTIS), which includes a person on watch who provides further information to vessels and warns them of high-risk situations or errors. USCG or industry-sponsored personnel can staff VTISs. The highest level VTSs, such as those in Prince William Sound (Alaska), Seattle, and New York, are staffed by a captain of the port with authority to order vessels to follow instructions in situations of extreme risk.
Maritime Risk Assessment
In January 1997, the USCG released its initial "Risk-Based Decision-Making Guidelines." Risk-based decision making is a "process that organizes information about the possibility for one or more unwanted outcomes into a broad, orderly structure that helps decision makers make more informed management choices" (USCG 2003, p. 1). The guidelines cover the standard quantitative risk assessment (QRA) tools used to study nuclear power and chemical production plants (Bedford and Cooke 2001), namely, failure mode and effect analysis, fault trees, event trees, and hazard and operability analysis, that have been used to analyze maritime static systems, such as offshore oil and gas platforms (Pate-Cornell 1990), but have proved of little use for analyzing entire port systems (Fowler and Sorgard 2000).
We have assessed risk in several ports: Prince William Sound's oil-transportation system (Merrick et al. 2000, 2002), Washington State's ferry system (Grabowski et al. 2000, van Dorp et al. 2001), and San Francisco Bay's ferry system (Merrick et al. 2003). We used simulation to model the dynamic nature of each port system, combining simulation models with standard risk-assessment methods. The simulation models often identified trade-offs between targeting safety concerns with specific interventions and the migration of risk to other parts of the system (Merrick et al. 2000). Although these large-scale studies successfully assessed safety-intervention measures, identified safety trade-offs, and built stakeholder trust (Merrick et al. 2002), their cost and duration put such studies beyond the USCG's reach. It must consider many ports, inland waterways, and lakes. The USCG needs a tool to assist it in making decisions based on the trade-offs between targeting specific safety concerns and maximizing the overall level of safety in US ports and waterways.
The USCG performed two studies aimed at producing such a tool, its "Analysis of Ports' Needs" (USCG 1973) and its "Deployment Requirements for U.S. Coast Guard Pollution Response Equipment" (Maio et al. 1991). In both studies, the analysts applied multiple regression to nationwide accident data. They omitted many factors that affect risk because of lack of data, particularly data on human error in maritime operations, and thus their results were of limited utility (Harrald et al. 1992).
Making Decisions About Safety
To restart the decision process for allocating VTM technology after the failure of VTS 2000, the USCG sought a method of assessing risk in ports and waterways and identifying which ports needed new VTM technology. It also wanted to reduce the cost of assessing risk. We developed the ports and waterways safety assessment (PAWSA) model based on our experience in the Prince William Sound risk assessment (Harrald et al. 1998; Merrick et al. 2000, 2002) and in light of the dialog group's findings on the attributes of ports or waterways that affect safety.
At first, USCG personnel considered simply gathering data on these attributes for ports and waterways in the hope of determining which performed poorly on many attributes and thus identifying high-risk systems. However, this procedure did not produce useful answers....
|
