Toolsets/ Human Factors
Chapter 7: Integrate Human Factors in
System Engineering
PURPOSE |
This chapter describes the human factors engineer's role in system engineering.
System engineering is the translation of operational requirements into design,
development, and implementation concepts and requirements. The Human Factors
Coordinator assists the Government's and contractor's system engineering
effort by integrating human factors within the acquisition process. Identifying
the human performance boundaries, risks, trade-offs, and opportunities of
the system engineering options and alternatives does this.
Human engineering is applied during design, development, and implementation
of systems, software, and facilities to effectively integrate human resource
and performance considerations. A human engineering effort is conducted
to:
- Develop or improve human interfaces of the system,
- Achieve required effectiveness of human performance during system operation,
maintenance, and support, and
- Make economical demands upon personnel resources, skills, training,
and costs. |
| TIMING |
Human factors in the system engineering process is initiated in the Investment
Analysis phase of the acquisition process and continues through Solution
Implementation and into In-Service Management. |
| "HOW TO" |
System engineering is an interdisciplinary approach to evolve and verify
an integrated and lifecycle-balanced set of system product and process solutions
that satisfy customer needs.
The Human Factors Coordinator assists in the system engineering task
by contributing information related to design enhancements, safety features,
automation impacts, human-system performance trade-offs, ease of use, and
workload. The Human Factors Coordinator also assists in identifying potential
task overloading or skill creep for system operators and maintainers. Where
user teams or operator juries and representatives participate in achieving
an operational viewpoint to design, the IPT human factors engineer complements
the effort to ensure performance data represents more than individual preferences.
Optimally, the Human Factors Coordinator participates fully in system engineering
design decisions. |
|
While the actual design and development work may be completed by either
the government or the contractor, the IPT Human Factors Coordinator (in
conjunction with the Human Factors Working Group) provides close, continuous
direction throughout the acquisition process. To accomplish this, the Human
Factors Coordinator reviews all documentation for human performance impacts
that will affect total system performance and exercises his or her responsibility
by participating in technical meetings and system engineering design reviews.
The human engineering effort includes those system engineering tasks
and activities listed in Table 7-1. The human engineer actively participates
in four major interrelated areas of system engineering:
- Planning
- Analysis
- Design and Development
- Test and Evaluation |
Step 1:
Human Engineering in Planning |
Human engineering planning is performed to ensure effective and efficient
support of the system engineering effort for human performance and human
resource considerations. Human engineering program planning includes the
human factors tasks to be performed, human engineering milestones, level
of effort, methods to be used, design concepts to be utilized, and the test
and evaluation program, in terms of an integrated effort within the total
project. |
Table 7-1. Human Factors-Related Tasks and Activities |
- Prepare operationally realistic mission profiles and mission scenarios.
- Prepare functional flow block diagrams for the system.
- Perform a functional analysis of each flow block and define operational
and support equipment and facilities requirements.
- Prepare system and subsystem schematic block diagrams.
- Study detailed functions, environment and technical design requirements
to allocate tasks to personnel, equipment, software, or some combination
thereof.
- Prepare operation and maintenance timeline analyses to determine system
reaction time.
- Prepare and analyze operations and maintenance workload and task data
to influence equipment and procedure design, and to determine personnel
requirements.
- Identify training implications.
- Conduct trade studies.
- Participate in preparation of specifications for the system.
- Participate in design reviews, demonstrations, and test and evaluation
activities. |
|
The human engineering planning effort specifies the documentation requirements
and assists in the coordination with other program activities. Government
and contractor documentation provides traceability from initially identifying
human engineering requirements during analysis and/or system engineering,
through implementing such requirements during design and development, to
verifying that these requirements have been met during test and evaluation.
The efforts performed to fulfill the human engineering requirements must
be coordinated with, but not duplicate, efforts performed by other system
engineering functions. |
Step 2:
Human Engineering in System Analysis
|
To support system analysis, the functions that must be performed by the
system in achieving its objective(s) within specified mission environments
are analyzed for their human factors implications and alternatives. Human
engineering principles and criteria are applied to specify humansystem
performance requirements for system operation, maintenance and support functions
and to allocate system functions to automated operation and maintenance,
manual operation and maintenance, or some combination thereof. Function
allocation is an iterative process to achieve the level of design detail
appropriate for the level of system definition.
Functional Analysis. Human factors functional analyses
are conducted to determine information flow and processing required by the
users to accomplish the system objective(s) including the decisions and
operations to be performed.
Human roles in the system are identified and distinguished from machine
functions. Estimates of human (vs. machine) processing capability in terms
of workload, accuracy, rate, and time delay are prepared for each potential
operator and maintainer information processing function. Comparable estimates
of equipment capability are also made. These estimates are used initially
in determining allocation of functions and are refined at appropriate times
for use in definition of operator and maintainer information requirements.
Functional Allocation. From projected operator and maintainer
performance data and known constraints, analyses and trade-off studies are
conducted to determine which system functions should be machineimplemented
or software controlled and which should be reserved for the human operator
and maintainer. Allocation of functions considers the error and delay risks
for each design alternative so that designs prevent or minimize the impact
of, or sensitivity to, situations where human decisions are made under conditions
of uncertainty, time constraints, or workload stress. The potential and
opportunities to influence human or equipment capabilities through personnel
selection and training as well as through equipment and procedure design
are also considered.
Design Configuration. Human engineering principles and criteria
are applied along with all other design requirements to identify and select
the particular equipment to be operated and maintained by personnel. The
selected design configuration should reflect human engineering inputs to
satisfy the functional and technical design requirements and to ensure that
the equipment will meet the applicable human engineering design criteria.
Task Analysis. Human engineering principles and criteria are applied
to analyses of tasks and workload. These analyses are provided as basic
information for developing preliminary manning levels, equipment procedures,
personnel skill requirements, training needs, and communication requirements.
A task analysis is conducted as a basis for making design concept decisions.
Time requirements for tasks are evaluated with respect to task duration
versus time availability, task sequencing, and task simultaneity. Task requirements
are evaluated with respect to accuracy; precision; completeness; and the
effects of task feedback, error tolerance, and error recovery on performance.
Those tasks identified during human engineering analyses that require critical
human performance are analyzed in greater detail.
Operator and maintainer workload analyses are performed and compared
with performance criteria. To avoid overloading or underloading, the degree
to which demands of any task or group of tasks tax the attention, capacities,
and capabilities of system personnel (and thus affect performance) are also
evaluated. Sensory, cognitive, and physiological limitations are considered.
The workload analyses help determine operational sequences and task times.
Humansystem interface design incompatibilities and excessive skill
and physical requirements, identified by task or workload analyses, are
corrected by changing design or restructuring tasks to preclude degraded
human performance. |
Step 3:
Human Engineering in Detail Design |
During detail design, the human engineering requirements are converted
into detail engineering design features. Design of the equipment should
satisfy humansystem performance requirements and meet the applicable
human engineering design criteria. The human factors engineer participates
in design reviews and engineering change proposals for those items having
a human interface.
Tests and Studies. The Government and contractor conduct experiments,
tests, simulation, and studies to resolve human engineering problems specific
to the system. Experiments, tests, and studies are performed in a controlled
environment with representative users in a realistic operating environment
in order to validate design goals and system performance objectives. included:
system layout, pand layout, control, communicadoa sys~m, indindual equipment
Drawings and Representations. Human engineering principles and
criteria are reflected in the engineering drawings and computer-aided design
representations to ensure that the final product can be effectively, efficiently,
reliably, and safely used and maintained. Design, as reflected in such drawings,
should comply with applicable human engineering criteria. The human factors
engineer reviews all layouts and drawings having potential impact on human
performance or interface and identifies for corrective action those designs
which may induce human error, excessive delay, or be unsafe. design, and
other drawings d~pictingequip~nent important to ~rstem operation and maintermnce
by
hwnan operators Design, reBected by such drawings, ~han cemply with applicable
cnt~e of
Environmental Conditions. Human engineering principles and criteria
are applied to detail design of work environments to be used by system personnel.
Design of work environments which affect human performance, under normal,
unusual, and emergency conditions, should consider the following: cond~tions.
- Acoustic noise and vibration.
- Adequate space for personnel, their movement, and their equipment.
- Adequate physical, visual, and auditory interface between personnel
and their equipment including eye positions in relation to display surfaces,
controls, and other visual areas.
- Safe and efficient walkways, stairways, platforms, and inclines.
- Provisions to minimize physiological stresses.
- Provisions to minimize physical fatigue.
- Equipment handling provisions and tools.
- Safe and error-proof equipment installations.
- Protection from chemical, biological, toxicological, radiological,
thermal, mechanical, electrical, and electromagnetic hazards.
- Optimum illumination commensurate with anticipated visual tasks.
Procedures. Based upon the human performance functions and tasks
identified by human engineering analyses, the human engineer applies the
necessary principles and criteria to the development of procedures for operating
and maintaining the system. This effort ensures that the human functions
and tasks are organized and sequenced for efficiency, safety, and reliability.
Software. The human engineer applies the appropriate principles
to the software design in those systems where software determines part of
the human interface. Software that affects controls and displays is evaluated
for the impact on the humansystem interface. Automated system functions
requiring human monitoring or intervention are considered as part of the
humansystem interface. Multifunction controls and displays that vary
in function are also part of the humansystem interface.
Technical Documentation. Human engineering is applied to the development
of manuals, including illustrations, to ensure thoroughness, technical accuracy,
suitable format of information presentation, appropriate reading level,
technical sophistication required, and clarity. |
Step 4:
Human Engineering in Test and Evaluation |
The Government and contractor establish and conduct a test and evaluation
program that addresses human factors to:
- Ensure fulfillment of the applicable human performance requirements;
- Demonstrate conformance of system, equipment, and facility design to
human engineering design criteria;
- Confirm compliance with system performance requirements where human
performance is a system performance determinant;
- Secure quantitative measures of system performance which are a function
of the human interaction with equipment; and
- Determine whether undesirable design or procedural features have been
introduced.
The fact that the above may occur at various stages in system development
should not preclude a final human engineering verification of the complete
system.
Human engineering testing is incorporated into the system test and evaluation
program and is integrated into engineering design and development tests,
demonstrations, acceptance tests, fielding and other implementation assessments.
Compliance with human engineering requirements should be tested as early
as possible. Human engineering findings from design reviews, mockup inspections,
demonstrations, and other early engineering tests should be used in planning
and conducting later tests. Human engineering test planning is directed
toward verifying that the system can be operated, maintained, and supported
by user personnel in its intended operational environment.
Human engineering test planning should also consider data needed or to
be provided by operational test and evaluation. Test planning includes methods
of testing (e.g., use of checklists, data sheets, test participant descriptors,
questionnaires, operating procedures, and test procedures), schedules, quantitative
measures, test criteria and reporting processes.
Human engineering portions of tests include:
- Performance of task or mission;
- Critical tasks;
- Representative samples of noncritical, scheduled and unscheduled
maintenance tasks;
- Personnel who are representative of the range of the intended user
populations;
- Proposed job aids, new equipment training programs; training equipment,
and special support equipment;
- Collection of task performance data in actual operational environments;
- Identification of discrepancies between required and obtained task
performance; and
- Criteria for acceptable performance.
Unfavorable outcomes occurring during test and evaluation are subjected
to a human engineering review to differentiate between failures of the equipment
alone, failures resulting from humansystem incompatibilities and failures
due to human error. Human-system incompatibilities and human errors occurring
in the performance of critical tasks are analyzed to determine the reason
for their occurrence and to propose corrective action(s). |
CHECKLIST
QUESTIONS |
- Has the human engineering effort been planned as an integrated portion
of the overall system effort? |
|
- Has the human engineering effort been coordinated with other system engineering
functions? |
|
- Has a functional analysis been conducted to determine information flow
and processing required? |
|
- Have the system functions been properly allocated between the hardware,
software, and the human? |
|
- Does the design configuration conform to human engineering design criteria? |
|
- Have the results of task and workload analyses been used to influence
system design? |
|
- Have required human performance tests and studies been identified? |
|
- Does the human engineer review all drawings which have a human interface
or impact human performance? |
|
- Does the system design reflect expected environmental conditions? |
|
- Is system software subjected to a human engineering review? |
|
- Have human engineering testing requirements been incorporated into the
system test and evaluation requirements? |
|
- Have unfavorable outcomes during test and evaluation been subjected to
a human engineering review? |
|