Human Factors Engineering (HFE) is a multidisciplinary effort to generate and compile information about human capabilities and limitations and apply that information to equipment, systems, software, facilities, procedures, jobs, environments, training, staffing, and personnel management to produce safe, comfortable, and effective human performance. It focuses on how people interact with tasks, machines (or computers), and the environment.
When human factors is applied early in the acquisition process, it enhances the probability of increased performance, safety, and productivity; decreases lifecycle staffing and training costs; and becomes well-integrated into the program’s strategy, planning, cost, and schedule baselines, and technical tradeoffs. Changes in operational, maintenance or design concepts during the later phases of a project are expensive and entail high-risk program adjustments. Identifying lifecycle costs and human performance components of system operation and maintenance during requirements definition decreases program risks and long-term operations costs.
HFE integration is a Systems Engineering function that translates operational requirements into design, development, and implementation of concepts and requirements. The Human Factors Engineer assists the sponsor’s and contractor’s system engineering effort by integrating human factors within the project development and management process. Identifying the human performance and safety boundaries, risks, trade-offs, and opportunities of the system engineering options and alternatives does this. A HFE effort is conducted to:
- Develop or improve human interfaces of the system,
- Achieve required effectiveness of human performance during system operation, maintenance, and support,
- Make economical demands upon personnel resources, skills, training, and costs.
HFE is primarily concerned with designing human-machine interfaces consistent with the physical, cognitive, and sensory abilities of the user population. Human-machine interfaces include: 
- Functional interfaces (functions and tasks, and allocation of functions to human performance or automation);
- Informational interfaces (information and characteristics of information that provide the human with the knowledge, understanding, and awareness of what is happening in the tactical environment and in the system);
- Environmental interfaces (the natural and artificial environments, environmental controls, and facility design);
- Cooperation interfaces (provisions for team performance, cooperation, collaboration, and communication among team members and with other personnel);
- Organizational interfaces (job design, management structure, command authority, policies and regulations that impact behavior);
- Operational interfaces (aspects of a system that support the successful operation of the system such as procedures, documentation, workloads, job aids);
- Cognitive interfaces (decision rules, decision support systems, provision for maintaining situational awareness, mental models of the tactical environment, provisions for knowledge generation, cognitive skills and attitudes, memory aids); and,
- Physical interfaces (hardware and software elements designed to enable and facilitate effective and safe human performance such as controls, displays, workstations, worksites, accesses, labels and markings, structures, steps and ladders, handholds, maintenance provisions, etc.,).
The human factors engineer participates in four major interrelated areas of the system engineering process:
- Design and Development
- Test and Evaluation