Human Factors Engineering (HFE) is an integral
part of the systems engineering process. In order to assure mission
success, all factors that affect the system performance and readiness
must be considered. In fact, people are a significant part of
the operational system in every case. We can only guarantee results
when we are able to predict how the hardware, software, and human
elements are going to perform. We can readily expect consistent
performance of equipment. People, on the other hand, process information
and communicate differently, derive decisions in a variety of
ways, and carry out tasks in a less constrained manner. Therefore,
the design must facilitate the human interface such that human
error potential is minimized or eliminated, tasks are simple to
understand and can be readily accomplished, and the impact of
decisions is clear.
Human Factors engineering should identify and be familiar with
the functions and tasks to be performed by the system and the
operational environment. This allows development of an understanding
of the overall system dynamics and the development of a valid
operations concept. This should be followed by a complete analysis
of the capabilities and limitations of system users. A task trade-off
analysis is recommended to establish an understanding of which
tasks are best performed by the human and which are best performed
by the hardware and software. In addition, this understanding
provides the groundwork for task and interface design to ensure
that the user can successfully perform the required tasks. Finally,
apply a consistent set of rules for designing the interface. The
design should meet specific user requirements and provide the
functionality to meet those requirements.
1.2.1 Overall HSI Objectives
The key to a successful HSI strategy is integration--not only of the system requirements for the seven elements (manpower, personnel, training, system safety, health hazards, human factors and survivability) but of their interactions with each other and with the hardware and software design. Optimizing total system performance entails trade studies between the seven HSI elements to achieve the most effective mix to support the system; and between the combined elements and the system platform to determine the most effective, efficient, affordable design. The results of these integration efforts should be reflected in updates to the requirements, objectives and thresholds in the ORD.
Values for objectives and thresholds, and definitions for parameters contained in the ORD, TEMP, and APB, shall be consistent. This ensures consistency and thorough integration of program interests throughout the acquisition process. For example, if the maintenance ratio (MR) established in the ORD, and included in the baseline and TEMP, are consistent, the manpower community should be able to use the MR value from the test results to establish manpower requirements in the manpower estimate. User participation in each acquisition phase is essential to ensure this consistency.
The overall objectives of HSI can be may be categorized as follows:
1.2.1.1 HSI will influence design by addressing human requirements, capabilities and limitations. The implications of this objective are that HSI will:
1.2.1.1.1 Address human performance and safety issues and concerns early in system acquisition;
1.2.1.1.2 Define the roles of humans in systems operations and maintenance early in system development;
1.2.1.1.3 Identify deficiencies and lessons learned in baseline comparison systems;
1.2.1.1.4 Apply simulation and prototyping early in the design process;
1.2.1.1.5 Apply human-centered design;
1.2.1.1.6 Apply human-centered test and evaluation.
1.2.1.2 HSI will enhance affordability by addressing the costs associated with operational and maintenance manpower; training; personnel non-availability due to accident; expected human error rates; expected time to repair; requirements for supportability; and requirements resulting from expected system downtime.
1.2.1.3 HSI will contribute to risk reduction by mitigating critical human system factors in design alternatives that will have a significant impact on readiness, life cycle costs, schedule, or performance. These include complex tasks; environments and environmental controls; equipment design features; maintenance requirements; information requirements; user-computer interface features; manning requirement; workloads; personnel skill levels; training requirements; and hazards to personnel health and safety.
1.2.2 Objectives by HSI Domain
1.2.2.1 Manpower objectives: numbers of required personnel, either in quantitative terms or as compared with the predecessor system.
When manpower and training constraints are assessed, the focus should be on what is design sensitive. For instance, when addressing manpower, the manpower should be split into two categories: that which is driven by the design of the system and that which is not.
(1) Manpower requirements that are not driven by the design of the system should be quantified for inclusion in manpower and cost estimates and O&S cost objectives. However, objectives and thresholds do not have to be developed for this manpower.
(2) Thresholds and objectives should be established for that portion of the manpower that is driven by the design. For example, maintenance workload is derived, in part, from the frequency and duration of maintenance actions. Reliability and maintainability are major contributors to maintenance workload and manpower. However, manpower factors that are actually used by the manpower community to determine the maintenance manpower, (such as maintenance ratios), usually serve as the best objectives and thresholds for the maintenance manpower. Careful attention must be paid to what type of maintenance tasks are covered by the manpower factors that are used as thresholds and objectives. For instance, it is important to clarify whether trouble shooting and indirect productive tasks are included in the manpower factors. Once these clarifications are made, the definitions for HSI objectives or thresholds contained in the ORD, TEMP, MER, and APB should be consistent to ensure consistency throughout the acquisition process.
(3) Other factors, such as equipment usage rates (optempos), levels of maintenance, and use of contract services impact the manpower numbers and must be considered when setting objectives and thresholds. Because of increased performance and capability, modernized systems may not be acquired on a one-for-one replacement basis. Decisions concerning the size of the buy and replacement rates must also be considered when setting objectives and thresholds.
1.2.2.2 Personnel objectives: no qualitative increase in the characteristics of operators, maintainers, or repairers; quantitative goals for personnel capabilities, if available.
When establishing personnel requirements, review recruitment trends, personnel policy decisions, occupational specialties, skill levels, and projected military personnel inventory shortfalls for operators, maintainers, and support personnel. Identify constraints on combining, modifying, or establishing new occupational specialties, or requirements for continuing to use existing occupational specialties. Personnel decisions will help to determine the user population (sometimes referred to as the "target audience"). This is important since human attributes of the user population may change based on recruitment trends and personnel policy decisions. For instance, physical (weight, anthropometric and strength) attributes and limitations had to be revised based on the decision to include women in combat support positions.
Rather than listing specific occupational specialties of the target audience, it may be more appropriate to refer to the target audience when setting personnel constraints. For instance, it may be appropriate to require that "operational maintenance and support tasks be commensurate with the aptitude levels listed in the target audience description for the XX weapon system," or that the "weapon system not change the operator/maintainer skill and general knowledge requirements in the target audience description (TAD)." However, it is important to allow as much flexibility as possible, particularly early in the acquisition process. For instance, if program analyses indicate the system will require excessive training times, it may be appropriate to change or set specific constraints for skill-levels or education levels, or to require special skills or knowledges to reduce or eliminate long technical training times.
Later in the acquisition process, personnel requirements may be described in terms of ranges of population that are tied to the user population. For instance, the ORD may require "performance of critical maintenance tasks with 95% reliability by 90% (5th to 95th percentile) of the target audience."
1.2.2.3 Training objectives: no more than the number of training hours in the predecessor system; statements addressing the projected use of advanced training technology or techniques, e.g., embedded training and intelligent tutoring.
When developing the training/instructional system, alternative training concepts, strategies, and tools such as computer based and interactive courseware, simulators, and embedded training should be considered.
(1) Emphasis should be given to including advancements in training technology, such as expert systems, intelligent tutors, virtual environments, and embedding training capabilities within actual defense systems, to enhance the user's capabilities, improve readiness, and reduce individual and collective training costs over the life of the defense system. For instance, interactive electronic technical manuals provide a training forum that can significantly reduce schoolhouse training and skill level requirements for maintenance personnel while actually improving their capability to maintain an operational system. An on-board "just-in-time mission rehearsal capability" supported by the latest intelligence information or an integrated global training system/network that allows team training and participation in large scale mission rehearsal exercises can be used to improve readiness.
(2) Careful consideration and priority should be given to the use of embedded training (e.g., a training program contained as a tutorial and as a dynamic simulation in an operational radar). Analysis should be conducted to compare the embedded training with other more traditional training media (e.g., simulator based training, traditional classroom instruction, and/or maneuver training). The analysis should compare the costs and the impact of embedded training (e.g., additional unit maintenance workload). It should also compare the learning time and level of effectiveness (e.g., higher "kill" rates and improved maintenance times) achieved by embedded training. When making decisions about whether to rely exclusively on embedded training, analysis must be conducted to determine the timely availability of new equipment to all categories of trainees (e.g., Reserve and Active Component units or individual members). For instance, a National Guard tank battalion which stores and maintains its tanks at a central maintenance/training facility may find it more cost effective to rely on mobile simulator assets to train combat tasks rather than transporting its troops to the training facility during drill weekends. A job aid for embedded training costing and effectiveness analyses is: "A Guide for Early Embedded Training Decisions," US Army Research Institute for the Behavioral and Social Sciences Research Product 96-06.
(3) In every case, the paramount goal of the training/instructional system must be to develop and sustain a ready, well trained unit while giving strong consideration to options that reduce life cycle costs.
1.2.2.4 Human Factors Engineering (HFE) objectives: the minimum goal should be to ensure that the system is designed to accommodate personnel requirements. If there are known human performance or workload problems with the predecessor system, the goals should address the elimination or reduction of these problems. A goal should also address the establishing of a HFE program to ensure that human performance and workload isues detected during system development are eliminated.
The ORD should state broad cognitive, physical, or sensory characteristics for the operators, maintainers or support personnel in terms of "requirements" whenever such human performance characteristics directly contribute to or constrains system performance. State human factors requirements in terms of measurable capabilities or limitations (to include reliability) whenever possible, and base requirements on an assessment of the user population or target audience.
(1). Cognitive requirements concern the capability to think and process information. They typically concern mental response times and operational requirements that can cause cognitive overload. When the ORD includes total system response times or total system operations that require human participation, the requirements must specifically state all human-in-the-loop requirements. Requirements for human control of system operations, manual override of specific functions, and specific requirements for human-system interfaces (operator/station interface, pilot/vehicle interface, and other data fusion and display requirements) must be clearly defined. These requirements should not be stated in terms of system solutions, however. For instance, rather than requiring a "fully integrated cockpit with head up or head mounted displays," the requirement should be for a "fully integrated cockpit that allows checking of aircraft instruments and weapon systems without requiring the pilot to go heads down." Critical operational requirements requiring human employment of the weapon system, such as high-speed nap-of-the earth flying, or a need for completely autonomous operations must be clearly stated. Stipulating such operational requirements is important since they may entail an excessive number of complex tasks that can result in cognitive overload and safety problems. For example, concerns about cognitive overload led to a series of cognitive workload analyses and simulator tests to verify whether the Comanche helicopter could be designed to be a single pilot helicopter. The Army found that a single pilot could not handle both high-speed nap-of-the-earth flying and extensive mission equipment package responsibilities and subsequently redesigned the helicopter before a prototype was ever built.
(2). Physical requirements typically include anthropometric accommodation (measurements of the human body), strength, and weight requirements. These type requirements are often tied to system safety and health hazard concerns. For instance, when the user requires that the weapon system be "one-man portable," performance based thresholds and objectives should be developed that take human strength limitations of the user population, the operational concept, environment, and other related factors (such as the weight of other required equipment) into consideration. To ensure that the average soldier can operate and maintain the system, it may be appropriate to state requirements in terms of the user population. For example, it may be appropriate to require that "the system be capable of being maintained by the 5th through 95th percentile soldiers wearing standard battle dress, or arctic and MOPP IV protective garments," or that the crew station accommodate a female/male population, defined by the 5th-95th anthropometric female/male soldier, for accomplishment of the full range of its mission functions."
(3). Sensory requirements typically cover visual, olfactory (smell), and hearing requirements. The ORD should identify operational considerations that effect sensory processes. For example, systems may need to operate in noisy environment where weapons are being fired or operated on an overcast moonless night with no auxiliary illumination.
1.2.2.5 System safety and health hazards objectives: if there are any known safety problems in the predecessor system, they should be described and goals should be stated to eliminate these problems. A goal should also address the establishing of a system safety program to ensure that safety issues detected during system development are eliminated.
If there are any known health hazards in the predecessor system, these should be described and goals should be stated to eliminate these hazards. A goal should also address the establishing of a health hazard assessment (HHA) program to ensure that hazards detected during system development are eliminated.
During early stages of the acquisition process, sufficient information may not always be available to develop a complete HHA report. Therefore, an initial report is prepared identifying the areas where more data is needed. As additional information becomes available, the initial report is refined and updated to provide a complete report on identified health hazards. Health hazard assessments should include cost avoidance figures to support trade-off analysis. There are nine health hazard issues typically addressed in a health hazard analysis (HHA):
(1) Acoustical Energy. The potential energy that transmits through the air and interacts with the body to cause hearing loss or damage to internal organs.
(2) Biological Substances. The exposure to microorganisms, their toxins, and enzymes.
(3) Chemical Substances. The hazards from excessive airborne concentrations of toxic materials contracted through inhalation, ingestion, and skin or eye contract.
(4) Oxygen Deficiency. The displacement of atmospheric oxygen from enclosed spaces or at high altitudes.
(5) Radiation Energy. IONIZING: The radiation causing ionization when interfacing with living or inanimate mater. NONIONIZING: The emissions from the electromagnetic spectrum with insufficient energy to produce ionizing of molecules.
(6) Shock. The mechanical impulse or impact on an individual from the acceleration or deceleration of a medium.
(7) Temperature Extremes and Humidity. The human health effects associated with high or low temperatures, sometimes exacerbated by the use of a materiel system.
(8) Trauma. PHYSICAL: The impact to the eyes or body surface by a sharp or blunt object. MUSCULOSKELETAL: The effects to the system while lifting heavy objects.
(9) Vibration. The contact of a mechanically oscillating surface with the human body.
1.2.2.6 Personnel survivability objectives: System design features that reduce the risk of fratricide, detectability, and probability of being attacked and that enable the crew to withstand man-made hostile environments without aborting the designated mission or suffering acute chronic illness, disability, or death. For all acquisition programs designated as mission-critical systems, survivability from all threats found in the various levels of conflict shall be considered and fully assessed during Phase 1. (see DoD 5000.2-R, section 4.4.1).