The probability that the total system will perform correctly when it is available is the probability that the hardware/ software will perform correctly, times the probability that the operating environment will not degrade the system operation, and times the probability that the user will perform correctly. By defining the total system this way, human performance is identified as a system component. A system can operate perfectly from an engineering sense in a laboratory or at a demonstration site and then not perform well when the users operate and maintain it at a field location. The Total System Performance will increase significantly by increasing the probability that the operator can perform the task effectively in the appropriate environment. (FAA.gov)
Hardware and software design affects the accuracy of operator task performance and the time required for each task. Applying human factors principles to the “total system” design will increase performance accuracy, decrease performance time, and enhance safety. Research has shown that designing the system to improve human performance is the most cost-effective and safe solution, especially if done early in the acquisition process.
Overarching Human Factors Principles
- Honor The User (The user defines requirements – but only in a structured, data-driven way.)
- To Err Is Human (People are not machines; machines are not perfect; design the interface to tolerate both errors.)
- Human Factors Is Not Free (Plan the resources for human factors program support.)
- Human Factors Requires Experts (The application of human factors engineering is neither easy nor common sense – except in retrospect of an incident or accident or poor design; co-locate human factors resources near the project/program teams they serve.)
- People Are the Same; Individuals Are Different (Design for people sameness & tolerance of measured differences, especially in their skill and performance.)
- Early Operator and Maintainer Decisions Drive Safety and Lifecycle Support Costs (Identify early in the program development process a requirement to subject every product to an “Out-of-Box” human factors study.)
- Operator and Maintainer Skill Is a Function of Aptitude and Training (Training is part of the system engineering and safety performance package.)
- Performance Is Measured in Terms of Time and Accuracy (Performance is a matter of degree – quantitatively and qualitatively determined; test for human performance early and often.)
- Task Safety & Performance Are Determined by the Design (Designs can improve or detract from task safety and performance.)
- Operator and Maintainer Performance Affect System Performance (How people use the system IS the measure of the system’s capabilities and risks.)
Source: FAA System Safety Handbook, Chapter 17: Human Factors Principles & Practices, Table 17-2: Overarching Human Factors Guidelines/Principles, December 30, 2000