As we work on a project for a client, I am reminded of the stark contrast in HF expectations across industries. Having grown up in the chemical industries managing PSM/RMP-covered processes, Human Factors (HF) has been “a thing” since 1992. HF was very much a steep learning curve and still is for many. I spent some time recently with a client who had many opportunities in the HF arena but, to their own demise, never could grasp real HF engineering (HFE) principles within their operations.
The items below are from my HFE Checklist used in our MOC and PSSR for “safety systems.” We use it to ensure the system we are developing meets the fundamental principles of HFE. I hope it helps those who embrace HF in the design, implementation/construction, operations, and maintenance of safety systems. The items make a nice “analysis” tool against any design, not just safety systems.
1) MAKE THE DESIGN CONSISTENT
Systems and equipment should be designed to be consistent, appearing, behaving, and responding the same throughout. [Galitz, 1993]
Definition: Consistent means adhering to the same principles with minimal variation. For systems, this entails maintaining a common design philosophy. Consistent design allows users to take general knowledge and skills learned from one system and apply it to other similar systems without extensive learning or training. [Source: DSTL-95-033, 1996]
2) BE CONSISTENT WITH THE USER MENTAL MODEL
Systems should be designed to decrease learning or training times to be consistent with the users’ mental model. [Source: DSTL-95-033, 1996]
The following are some areas that can be exploited to obtain consistency with user mental models in system design:
a. Analogy with real-life objects
b. Experience with similar systems
c. Previous operational experience
[Source: DSTL-95-033, 1996]
3) MINIMIZE INCONSISTENCY
If an occasional departure from consistent design is necessary to support user task performance, designers should minimize the extent of the inconsistency with the rest of the user interface. [Source: DSTL-95-033, 1996]
Standardize hardware and software. Hardware and software designs shall be standardized to the degree practical and compatible with system functions and purposes. [Source: MIL-STD-1472G, 2012]
Definition: Standardization refers to common user-interface features across multiple applications.
Standardized hardware would use consistent fasteners, switches, breakers, and connectors within and across equipment. When software is standardized, applications that address common functions employ the same user dialogs, interfaces, and procedures.
4) STANDARDIZATION SIMPLIFIES
Standardization simplifies maintenance procedures and reduces the tools required, the potential for human error, training time, skill requirements, inventory of spares, and documentation. [Source: MIL-STD-1472G, 2012; Department of Defense (MIL-HDBK-759C), 1995]
- Maintain identical interfaces for identical functions. Equipment with identical functions shall employ identical or similar interfaces. [Source: MIL- STD-1472G, 2012]
- Make controls, displays, marking, coding, labeling, and arrangement uniform. Controls, displays, marking, coding, labeling, and arrangement schemes shall be uniform for common functions of all equipment. [Source: MIL-STD-1472G, 2012]
- Make unique functions distinctive. Units of equipment or modules with unique functions should be distinctive in appearance and identification. [Source: DOE-HDBK-1140, 2001]
- Standardize terminology, look, and feel. Systems and equipment should have standardized terminology, look, and feel. [Source: DOD-HFDG-ATCCS, 1992]
STANDARDIZED TERMINOLOGY eliminates differences in names assigned to and descriptions of the same functions and features. A standardized look minimizes differences in the appearance of displays based on different styles. A standardized feel minimizes differences in the actions a user takes to interact with an application. [Source: Galitz, 1993]
Make functionally similar equipment interchangeable. Equipment with the same form and function shall be interchangeable throughout a system and related systems. [Source: MIL-STD-1472G, 2012]
Make functionally different equipment non-interchangeable. If equipment is not interchangeable functionally, it shall not be interchangeable physically. [Source: MIL-STD-1472G, 2012]
Make controls, displays, marking, coding, labeling, and arrangement UNIFORM. Controls, displays, marking, coding, labeling, and arrangement schemes shall be uniform for common functions of all equipment. [Source: MIL-STD-1472G, 2012]
Make unique functions distinctive. Units of equipment or modules with unique functions should be distinctive in appearance and identification. [Source: DOE-HDBK-1140, 2001]
STANDARDIZE TERMINOLOGY, LOOK, AND FEEL. Systems and equipment should have standardized terminology, look, and feel. [Source: DOD-HFDG-ATCCS, 1992]
Standardized terminology eliminates differences in names assigned to and descriptions of the same functions and features. A standardized look minimizes differences in the
appearance of displays based on different styles. A standardized feel minimizes differences in the actions a user takes to interact with an application. [Source: Galitz, 1993]
Make functionally similar equipment interchangeable. Equipment with the same form and function shall be interchangeable throughout a system and related systems. [Source: MIL-STD-1472G, 2012]
Make functionally different equipment non-interchangeable. If equipment is not interchangeable functionally, it shall not be interchangeable physically. [Source: MIL-STD-1472G, 2012]
5) INCORPORATE SAFETY FACTORS
System and equipment design shall incorporate applicable system and personal safety factors that affect human performance, including those that minimize human error in the operation and maintenance of the system under normal, degraded, and emergency or non-routine conditions. [Source: MIL-STD-1472G, 2012]
Provide a fail-safe design. A fail-safe design shall be provided for systems where failure could cause catastrophic damage, injury to personnel, or inadvertent equipment operation. [Source: MIL-STD-1472G, 2012]
Make systems error-resistant. Users shall be protected from making errors to the maximum possible extent. [Source: Martin & Dong, 1999]
To make a system error-resistant is to make it difficult for a user to make an error. Simplicity in design and the provision of clear information are tools to improve error resistance. Electronic checklists also have the potential to improve error resistance by providing reminders of items that need to be completed. [Source: Billings, 1991]
Make systems error-tolerant
Systems should be tolerant of human errors. [Source: Galitz, 1993]
To make a system error-tolerant is to mitigate the effects of human errors that are committed. Error tolerance can be improved by adding monitoring capabilities. [Source: Billings, 1991]
Warn of potentially unsafe actions. Systems and equipment should warn users before they initiate a task that may result in potentially serious consequences. [Source: Apple Computer Incorporated, 1995]
Identify safe and unsafe states and actions. Systems and equipment shall clearly identify safe and unsafe operating states and actions. [Source: NISTIR 4909, 1992]
Provide emergency procedures for critical systems. For critical software, systems, or equipment, there shall be a clear, step-by-step description of procedures to be conducted in the event of failure. [Source: NISTIR 4909, 1992]
Provide redundancy
There shall be redundant means to access systems and equipment that provide a critical function. [Source: NISTIR 4909, 1992]
Design systems to be modular. Systems and equipment should be modular in design. [Source: NISTIR 4909, 1992]
Definition: To be modular means to be designed with standardized or uniform components. The advantage of a modular design is that if one component fails, it is easier to replace.
Prevent damage through design
Design, location, procedural guidance, and suitable warning labels shall be provided to prevent equipment or personnel damage while being handled, installed, operated, or
maintained. [Source: MIL-STD-1472G, 2012]
Prevent misalignment and improper mounting
Equipment shall include physical features that prevent improper mounting or alignment, or at minimum, have labels or codes to identify proper mounting and alignment. [Source: MIL-STD-1472G, 2012]