The nation's ports and waterways are vital links in national, regional, and local intermodal transportation and economic systems. The safety of vessel operations in these waters and ultimately the underlying waterway design are under increasing scrutiny as a result of major shipping disasters on all coasts. At the same time, the overall costs of waterway projects, increased cost-sharing responsibilities of local project sponsors, and awareness of environmental impacts has increased pressure for more efficient waterway designs. This pressure in turn has motivated new and improved techniques to offset the traditional approach to waterway design, an approach that can result in channels of questionable safety, excessive cost, or both because of uncertainty, conservatism, and reliance on rules of thumb.

The economic importance of the ports and waterways system is reflected in the flow of cargoes through the system and in the substantial national investment to support waterborne commerce. About one-third of domestic intercity trade and almost all foreign trade by weight pass through the system each year. The annual waterway investment by the U.S. Army Corps of Engineers (USACE) alone is $1.23 billion. Additional federal government investments include construction, operation, and maintenance of aids to navigation.

State, port authority, and commercial investment has until recently

focused principally on port facilities, including berthing and cargo-handling capabilities. Funding of maintenance and modernization projects to assure efficient operation of the waterway system was primarily a federal responsibility until passage of the Water Resources Development Act of 1986. The act shifted much of the financial responsibility for expensive waterway improvement projects to local sponsors. This fundamental change in policy and escalating costs increased the importance of most-cost-effective waterway design as a means to help keep construction and maintenance costs affordable.

Shiphandling simulator technology is considered by many design engineers to be a potentially important and effective tool for waterway design. Interest is growing in the use of simulation technology to increase confidence in waterway designs and reduce the costs of construction and maintenance.

Shiphandling simulations based on available technology have been developed over the last 3 decades. Simulations have been used in a variety of contexts from training vessel crews and analyzing marine casualties to the evaluation of buoy placement. The use of simulation in the design process for modifying or developing channels and waterways is the most technologically demanding of these applications. Confidence in the application of simulators in channel design has been hampered by difficulties in assuring that the results of simulations reproduce what would have occurred in the real situation or provide sufficient value to justify their expense.

The related issues of choosing a simulator facility with suitable capabilities to address the design problem effectively, of having confidence in the results, and of integrating simulation results into the waterway design process were studied by an interagency committee in 1986. That study, convened and coordinated by the U.S. Army Corps of Engineers, recommended consultation with the National Research Council (NRC) on the role of shiphandling simulation in waterway design and supporting research (USACE, 1986b).

The NRC convened the Committee on Assessment of Shiphandling Simulation under the auspices of the Marine Board of the Commission on Engineering and Technical Systems.

Committee members were selected for their expertise and to ensure a wide range of experience and viewpoints. The principle guiding the constitution of the committee and its work, consistent with the policy of the NRC, was not to exclude members with potential biases that might accompany expertise vital to the study, but to seek balance and fair treatment. Committee members were selected for their experience in port and waterway design, hydrodynamic and mathematical modeling, computer simulation, sta

tistical analysis, ship control design, aviation and shiphandling simulation technology, and shiphandling. Academic, industrial, government, and international perspectives were also reflected in the committee's composition. Biographies of committee members are provided in Appendix A.

The committee was assisted by the U.S. Army Corps of Engineers, U.S. Coast Guard, U.S. Maritime Administration, and the U.S. Navy's Carderock Division, Naval Surface Warfare Center (formerly David Taylor Naval Ship Research and Development Center), all of which designated liaison representatives.

The committee was asked to conduct an interdisciplinary assessment of the state of practice of simulation of ship transits in restricted waterways, the adequacy of data input to simulators, and the validity of hydrodynamic and related models. The committee was further asked to develop guidance for determining the applicability and presentation of simulation results, provide guidance for determining the required and achievable accuracy of simulator results, and recommend research to resolve any discrepancies. However, assessment of human factors in shiphandling simulations, shiphandling theory, and waterway design theory were beyond the scope of study. The issue of competitive advantage associated with the economic potential of port regions to sponsor waterway projects, although an important factor in assessing the effects of the Water Resources Development Act of 1986, was also beyond the scope of study.

The committee reviewed available data and literature to determine the state of practice of simulator use in maritime activities, including the appropriateness of various levels of simulation to different port and waterway design objectives. This examination was supplemented by visits to simulator facilities and discussions with experts in the United States, Europe, and Japan, which were documented in detailed trip reports. Case studies of shiphandling simulator application to waterway design were developed and are included as Appendix C. A source reference list on mathematical models was prepared and included as Appendix D.

The audience for which this report was prepared consists of waterway designers, naval architects interested in the scientific issues involved with predicting the forces acting on a ship as it maneuvers in a constrained waterway, simulation experts knowledgeable in the computational and graphical presentation aspects of the technique, members of the maritime and general public who participate in the waterway design process, and decision makers affecting the use of simulation. Understanding shiphandling simulation for waterway design requires a simultaneous understanding of the science and practice of simulation and the context of waterway design in which simula

tion is used. Chapters 2, 3, and 4 provide this information as background because suitable, concise references are not available.

Chapter 1 provides an overview of the relationship of U.S. ports to the economy, port modernization needs, trends and issues affecting port and waterway development, general goals of waterway modernization, and how shiphandling simulators are used in achieving these goals.

Chapter 2 summarizes the harbor and waterway design process. It identifies the process used, participants, and design factors and issues.

Chapter 3 describes shiphandling simulators and their use in the waterway design process.

Chapter 4 discusses the two principal types of shiphandling simulations, those operating in real-time mode with human operators in the decision-making loop and those operating in fast time with human operators replaced by computer-based pilot models.

Chapter 5 discusses and assesses mathematical models used in channel design simulation.

Chapter 6 assesses simulator technology and the validity of using this technology in the design process.

Chapter 7 discusses practical applications of simulators in harbor and waterway designs.

Chapter 8 identifies research needs, including the framework for analysis and results, mathematical models, simulator fidelity, and guidelines for the level of simulation.

Chapter 9 provides the committee's conclusions regarding the state of practice and recommendations for using simulators in the waterway design process.

The committee gratefully acknowledges the generous contributions of time and information provided by liaison representatives, their agencies and organizations, shiphandling simulation practitioners, and the many individuals in government and other organizations interested in the application of shiphandling simulation to channel design.

Larry L. Daggett, U.S. Army Corps of Engineers, Waterways Experiment Station, participated in the site visits and in-depth interviews held in Europe, and provided technical support and reference materials. H. Paul Cojeen, U.S. Coast Guard, provided technical advice on navigational safety factors in design. Frederick Seibold, U.S. Maritime Administration, provided technical advice on his agency's prior research using simulators. David A. Walden, Carderock Division, Naval Surface Warfare Center, provided technical advice on ship hydrodynamics.

Special thanks are extended to members of the international design and shiphandling simulation community who met with the committee's delegation during its European visit and provided technical advice on the state of practice. The committee is indebted to: S. D. Sharma, Institute für Schiffbau, Hamburg; T. E. Shellin, Germanischer Lloyd, Hamburg; A. H. Nielsen, M. S. Chislett, and L. Wagner-Smitt, Danish Maritime Institute, Lyngby; M. Oosterveld, V. ten Hove, Jan P. Hooft, and J. Perdok, Maritime Research Institute, Wageningen, The Netherlands; W. Veldhuyzen, I. Onassis, Ing. W. de Joode, The Netherlands Organization for Applied Scientific

search, Delft, The Netherlands; J. W. Koeman and W. Ph. van Maanen, Port of Rotterdam; M. P. Bogarerts, Rijkswaterstaat, Rotterdam; and Ian McCallum, Maritime Dynamics, Lantrisant, Wales.

The committee gratefully acknowledges the many contributions of the late C. Lincoln Crane, Jr. As staff study director, Mr. Crane coordinated the committee's activities including the European trip, provided expert technical advice on ship maneuvering, and supported development of background papers and case studies.

The extraordinary cooperation and interest in the committee's work of so many knowledgeable individuals were both gratifying and essential.

Ports and waterways are vital links in local, regional, and national intermodal transportation and economic systems. The safety of vessel operations in these waterways and ultimately the underlying design are under increased scrutiny as a result of major shipping disasters on all coasts. Related issues are the standard shipping practice of scheduling large ships into waterways originally designed for smaller, earlier-generation vessels, the lengthy time needed for design through construction of waterway modernization projects, and the lack of impetus for design reevaluation for safety after a waterway has been constructed or altered.

Traditional waterway design practice relies heavily on rules of thumb and conservatism for margins of safety. At the same time, the overall costs of waterway projects and expanded cost-sharing responsibilities of local project sponsors imposed by the Water Resources Development Act of 1986 have increased pressure for more cost-effective waterway designs. One effect of the revised cost-sharing responsibilities has been to stimulate efforts to develop design tools that improve the cost-effectiveness of design.

Over the past several decades, development of some waterway designs in the United States and overseas has been aided by the use of hydrodynamic physical scale model and computer-based shiphandling simulations. Each provides alternative means for achieving refinements in design not verifiable with other design tools. New attention has been focused on the potential of simulations to improve cost-effectiveness while still providing ade-

quate margins of safety. These two approaches provide different capabilities and levels of control for assessing alternate project dimensions relative to ship behavior under the influence of human operators and environmental conditions.

Interest has increased in the use of computer-based simulations. With this medium, projects can be modeled mathematically rather than physically, conceptually permitting the modeling of any waterway with the same hardware; vessel pilots can be presented with realistic representations of the operating environment under varying but controlled conditions; and the computer capability for high-speed, automated simulations using mathematical models of pilot behavior can be used to generate a large number of vessel transits that would not be feasible in real time. The use of simulation for these purposes, although promising and used in several major waterway studies, has been incorporated in only a small number of waterway projects.

This study addresses three questions about the use of computer-based simulations for waterway design:

• Does simulation work?

• When should simulation be used?

• How can simulation be enhanced as a design aid?

Computer-based shiphandling simulations sponsored by government, port authorities, and the maritime industry have been used effectively as a waterway design tool by planners and engineers. The technique provides an improved means to assess the operability of a proposed waterway improvement by approximating vessel behavior in the full waterway operating environment, thereby offsetting the traditional reliance on rules of thumb to provide adequate margins of safety.

Six applications of simulation to channel design were selected for detailed examination by the committee after review of over 50 different applications for which detailed results were available. The six simulation studies chosen for case study included a wide range of situations and are representative of typical applications that could be applied to design studies for U.S. waterways. The six simulations examined were:

• a study sponsored by the Exxon Corporation (1980-1981) to determine the maximum-size oil tanker that could safely transit a narrow channel cutting obliquely across the Coatzacoalcos River, Mexico, at the entrance to a tanker loading facility;

• a State of Virginia-sponsored study (1980–1986) to improve existing channel designs for Hampton Roads ports so as to permit safe transit of deep-draft coal colliers in channels with 55-foot depths.

• A U.S. Army Corps of Engineers (USACE) study (1983–1984) performed by the agency's Waterways Experiment Station to verify the validity of the final design for a major ship channel improvement project in Richmond, California, that would permit the discharge of fully loaded 85,000-deadweight ton (DWT) tankers and partially loaded 150,000-DWT tankers.

• A Panama Canal Commission study (1983–1986) to determine the specific dimensions of the optimum navigation channel that would afford a reasonable balance between excavation cost and safety of modifications necessary to permit two-way traffic of Panamax-size vessels throughout the canal's length.

• A study sponsored by Port of Grays Harbor, Washington, (1986) and performed by the USACE Waterways Experiment Station to verify the feasibility of the final design for widening and deepening 24 miles of an estuary and bar channel, improving a highway bridge fender system, and replacing a railroad bridge.

• A study sponsored by Port of Oakland, California, (1986–1988) to develop alternative channel designs for the inner and outer Oakland harbors in order to find suitable designs that would open the port to larger, more cost-efficient containerships.

Scientific, quantitative validation of the results of simulations is not yet available. However, pilot participation in the validation process and pilot acceptance of simulations indicate that reasonable success can be achieved with the existing state of practice by re-creating a realistic piloting experience through modeling of waterway complexities, the physical environment, and operational factors. The case studies revealed that simulations can effectively aid in decision making by providing unique quantitative information for answering design questions associated with channel depth, width, geometry, dredging requirements, aids to navigation requirements, and tugboat assistance. Additionally, simulations have also provided a unique, common forum for discussion between design participants and an easily understood context for problem identification, conflict resolution, and decision making.

In some of the applications examined, the construction cost savings stemming from design changes developed using simulation were much greater than the cost of simulation. The committee believes that risks to shipping and the environment can be reduced through design refinements based on simulations, but this reduction is difficult to assess or express in monetary terms. Nevertheless, evidence from the six case studies shows that simulation technology can be effectively applied to the waterway design process with substantial benefits. Simulation models developed for waterway design can also be used in simulations conducted for training.

Simulation should be used when:

• Vessel operational risk is a significant design issue. Incorporation of human pilot skills and reactions in the prediction of the behavior of a vessel in a proposed waterway is unique to shiphandling simulation. Differences in risk resulting from a variety of critical environmental conditions can be identified. Aids to navigation requirements that can further reduce risk can also be assessed.

• Cost and design optimization is an issue. The effect on risk resulting from variations in the many design factors that define a waterway can be evaluated. This capability is an important decision aid in the assessment of the components of life-cycle costs. Simulation is particularly useful for assessing operational differences between design alternatives.

• Competing interests among technical and nontechnical participants in the waterway design process are an issue. Simulation provides a unique way to bring critical and contentious aspects of the design into focus. Design modifications to accommodate competing interests can be tested and the consequences displayed in formats that do not require technical expertise to assimilate and understand.

Because elements of these three issues are frequently associated with most waterway designs, the committee concluded that shiphandling simulation should be developed as a standard tool available for use in waterway design. The level of sophistication of simulations needed for this process depends on the particular design. However, guidelines for the appropriate level for a given situation are not available within the current state of practice.

Simulation is a highly technical art involving the integration of many skills: naval architecture, civil and marine engineering, piloting, computer techniques, and human engineering. In all of these areas, there are substantial unresolved issues. Confidence in the use of shiphandling simulation for waterway design is limited by issues of fidelity and the level of simulation required. Use is inhibited by cost, scheduling, and interpretation of the results. More use of simulation in the waterway design process could be motivated by:

• Reducing the costs of simulation.

• Developing a definitive guide to assist designers in choosing a simulator for specific applications. Although the cost of computer equipment needed for simulation has dropped significantly in recent years, the cost of

the labor-intensive set up and conduct of the simulation has increased. These latter costs and the duration of the simulation process are sensitive to the level of simulation required, but no guidelines exist for this choice.

• Developing minimum requirements for fidelity and validation of mathematical models of ship dynamics, waterway data bases, and the simulator environment including visual displays and bridge mock-up.

• Developing a better understanding of the behavior of ships in situations unique to waterway design. These situations include operation in the following conditions: with small under-keel clearance, near banks of arbitrary geometry or muddy bottoms, in sheared currents, and in close passage of other ships.

• Developing and validating a mathematical framework for extrapolating the results from a small sample of simulation runs to a prediction of the performance of future traffic in the waterway.

• Establishing a carefully composed, interdisciplinary validation team as a formal element in each simulation validation process.

Confidence in simulations can be increased through a systematic research program designed to address the preceding deficiencies. The committee recommends implementation of a research program that

• assesses the need for fidelity in the mathematical models and simulator hardware,

• develops ways to determine, assess and resolve the uncertain elements in mathematic models, and

• provides a capability for interpreting the results.