Human Systems Integration (HSI) is a robust process by which to design and develop systems that effectively and affordably integrate human capabilities and limitations. HSI should be included as an integral part of a total system approach to weapon systems development and acquisition. The Defense Acquisition Guidebook (DAG) states, “The total system includes not only the prime mission equipment, but also the people who operate, maintain, and support the system; the training and training devices; and operational and support infrastructure”.
Guidebook: Air Force Human System Integration Handbook
HSI is a multidisciplinary field of study composed of several basic areas: [1,2]
- Human Factors Engineering
- System Safety
- Health Hazards
- Personnel Survivability
HSI includes humans, in their different roles in the system (as operator, maintainer, trainer, designer, etc.). Systems including hardware, software, and processes (including the acquisition process and the design process), and the integration of all of these elements to optimize the performance and safety of the whole. The principle goal of HSI is to ensure a safe and effective relationship between the human and the system that meets the mission. HSI includes:
- Integrated and comprehensive analysis
- Design and assessment of requirements
- Concepts and resources for system manpower
- Safety and occupational health
There are three (3) key concepts that define an effective HSI program. 
- Systems are comprised of hardware, software, and human personnel all of which operate within a surrounding environment. Too often, acquisition systems programs fail to consider the human capacity or requirements as part of the system. This leads to poor task allocation between hardware, software, and human users or supporters. To promote ideal task allocation, it is critical that the human element be considered early in system development.
- Successful HSI depends upon the integration of the functional HSI domains into acquisition planning efforts such as participation on program High-Performance Teams (HPTs) and Integrated Product Teams (IPTs).
- HSI must be considered early in the requirements development phase of system design and acquisition. This will provide the best opportunity to maximize return on investment (ROI) and system performance. HSI requirements must be developed in conjunction with capability-based requirements generation through functional analyses within the Joint Capabilities Integration and Development System (JCIDS). HSI requirements will drive HSI metrics and embed HSI issues within the system design. After a system is designed, implementation of HSI oversights can be very expensive.
AcqLinks and References:
-  Air Force Human System Integration Handbook
- HSI and ESOH Handbook for Pre MS A JCIDS and AoA Activities – Oct 13
- Website: Naval Post Graduate School – Human System Integration
- Website: MIL-HDBK-759B: Human Factors Engineering Design for Army Materiel
- Website: Air Force Human Systems Integration Office