William F. Stubler

Human Factors Engineering Guidance for the Review of Advanced Alarm Systems

This report provides guidance to support the review of the human factors aspects of advanced alarm system designs in nuclear power plants. The report is organized into three major sections. The first section describes the methodology and criteria that were used to develop the design review guidelines. Also included is a description of the scope, organization, and format of the guidelines. The second section provides a systematic review procedure in which important characteristics of the alarm system are identified, described, and evaluated. The third section provides the detailed review guidelines. The review guidelines are organized according to important characteristics of the alarm system including: alarm definition; alarm processing and reduction; alarm prioritization and availability; display; control; automated; dynamic, and modifiable characteristics; reliability, test, maintenance, and failure indication; alarm response procedures; and control-display integration and layout.

Human Factors Challenges for Advanced Process Control

New human-system interface technologies provide opportunities for improving operator and plant performance. However, if these technologies are not properly implemented, they may introduce new challenges to performance and safety. This paper reports the results from a survey of human factors considerations that arise in the implementation of advanced human-system interface technologies in process control and other complex systems. General trends were identified for several areas based on a review of technical literature and a combination of interviews and site visits with process control organizations. Human factors considerations are discussed for two of these areas, automation and controls.

Integrating Verification and Validation with the Design of Complex Man-Machine Systems

Human factors evaluation is a critical process for ensuring the success of man-machine systems. Meister (1987a, b) describes more traditional methods for systems design, development and testing, and system effectiveness testing. However, recent advances in man-machine interface system (M-MIS) technology (i.e., sensors, processors, displays and controls, and the overall control room configuration) and the man-machine systems that they control have created the need for more sophisticated approaches to evaluation. In particular, special attention is needed to address (a) cognitive issues related to how operators develop and maintain awareness of the state of the controlled system and (b) crew coordination issues related to the ways that individuals interact with each other and the rest of the man-machine system to accomplish operational goals. These issues may be difficult and expensive to resolve if evaluation is left until late in the design process and tested using a production prototype or a full-scope, full-scale simulator. This paper proposes an alternative approach in which human performance issues are evaluated earlier in the design process using lower fidelity testbeds (e.g., part-task simulators) in addition to more traditional means. This approach requires a systematic evaluation framework for defining issues and specifying required attributes of testbed fidelity.

COMPUTERIZATION OF NUCLEAR POWER PLANT EMERGENCY OPERATING PROCEDURES.

Emergency operating procedures (EOPs) in nuclear plants guide operators in handling significant process disturbances. Historically these procedures have been paper-based. More recently, computer-based procedure (CBP) systems have been developed to improve the usability of EOPs. The objective of this study was to establish human factors review guidance for CBP systems based on a technically valid methodology. First, a characterization of CBPs was developed for describing their key design features, including both procedure representation and functionality. Then, the research on CBPs and related areas was reviewed. This information provided the technical basis on which the guidelines were developed. For some aspects of CBPs the technical basis was insufficient to develop guidance; these aspects were identified as issues to be addressed in future research.

Human factors considerations in control room modernization: trends and personnel performance issues

Advanced human-system interface (HSI) technology is being integrated into existing nuclear plants as part of plant modifications and upgrades. The result of this trend is that hybrid HSIs are created, i.e., HSIs containing a mixture of conventional (analog) and advanced (digital) technology. The purpose of the present research is to define the potential effects of hybrid HSIs on personnel performance and plant safety and to develop human factors guidance for safety reviews of them where necessary. In support of this objective, human factors issues associated with hybrid HSIs were identified. The issues were evaluated for their potential significance to plant safety, i.e., their human performance concerns have the potential to compromise plant safety. The issues were then prioritized and a subset was selected for design review guidance development.

Comprehensive Guidance for the Evaluation of Human-Systems Interfaces in Complex Systems

Advanced human-system interface (HSI) technologies are being developed in the commercial nuclear power industry. These HSIs may have significant implications for plant safety in that they will affect the ways in which the operator interacts with and supervises an increasingly complex system. The U.S. Nuclear Regulatory Commission (NRC) reviews the HSI aspects of nuclear plants to ensure that operator performance and reliability are supported. The NRC is developing guidance to support its review of these advanced designs. The guidance consists of an evaluation methodology and an extensive set of human factors guidelines which are used in one aspect of the evaluation. The paper describes the guidance development of the evaluation methodology and the guidelines. While originally developed for nuclear plant evaluation, the methodology is applicable to other types of complex human-machine systems as well.

When soft controls get slippery: User interfaces and human error

Many types of products and systems that have traditionally featured physical control devices are now being designed with soft controls - input formats appearing on computer-based display devices and operated by a variety of input devices. A review of complex human-machine systems found that soft controls are particularly prone to some types of errors and may affect overall system performance and safety. This paper discusses the application of design approaches for reducing the likelihood of these errors and for enhancing usability, user satisfaction, and system performance and safety.

Group-View Displays for Enhancing Crew Performance

Group-view displays present information to multiple personnel simultaneously. Recent developments in human-system interface technologies have the potential of increasing the effectiveness of group-view displays in control centers. While established human factors guidelines exist for many visual characteristics of group-view displays, limited guidance has been available regarding the functions that these display systems should provide to enhance crew performance in control room settings. This paper draws research findings from the areas of teamwork, computer-supported cooperative work, and human-computer interface design to describe four functions that group-view displays may perform to support various aspects of team performance in advanced control centers.

The Effects of Interface Management Tasks on Operator Performance in Complex Systems

The primary tasks performed by operators of complex computer-based systems involve high-level cognitive activities, such as monitoring, detection, situation assessment, and response planning and implementation. To perform these tasks satisfactorily, operators must also perform interface management (IM) tasks. These are secondary tasks such as display navigation and window manipulation performed to interact with the human-system interfaces (HSIs). We investigated the effects of IM tasks on primary task performance using information obtained from literature, discussions with experts, and visits to process control facilities. Evidence for two basic IM effect models was found. In the resource-limited effect model, primary task performance suffers because operator attention may need to be directed away from that task towards the IM task. In the data-limited efSect model, operators minimize their performance of IM tasks to concentrate on the primary tasks, thus failing to retrieve important information in a timely manner. The HSI characteristics that were strongly associated with the IM effects included: information volume and organization, display area, and HSI flexibility. These findings have implications for HSI design. First, HSIs should be designed to minimize the need for IM tasks when difficult, time-critical, or safety-critical tasks are being performed. This can mean providing sufficient viewing area to display all important information and controls simultaneously, thereby reducing the need to make repetitive transitions between displays. Second, the organization of the display networks should (1) be easily understood by operators so that the location of information in the computer system is readily known, and (2) minimize the need for navigation through the display network. This may require a display organizational scheme different than those commonly used, which are often based on the characteristics of the system rather than the tasks to be performed. Finally, although sufficient flexibility should be provided to enable operators to deal with unanticipated situations or where personal preference can improve performance, flexibility should be carefully evaluated to minimize the likelihood that working with the HSI becomes a complex decision-making task in itself.