Quantifying design exclusion
The key requirement for assessing design exclusion is the ability to relate users to the ergonomic features of a product (see figure). However, the direct link (dashed line) between the two cannot be found from existing data. Consequently, based on the data available, the link is explored through two relationships:
- product ergonomic features and user functional capabilities (sensory, cognitive and motion capabilities); and
- product ergonomic features and user physical attributes (anatomical dimensions such as height, reach, grip strength, etc.).
The core of the review process is the same for the ideal product, product requirements and the actual product, each following a four-step approach:
- Specify the context of use:
state any assumptions regarding the environment in which the product is used and the sequence of actions encountered when using the product.
- Assess the capability demands imposed:
determine the number of users excluded by the product by the product, subject to its defined context of use (and the reasons for their exclusion) and the number of users disadvantaged, but not excluded.
- Assess the physical attributes required:
determine the number of users excluded from using the product subject to its defined context of use and the reasons for their exclusion.
- Eliminate multiple counting:
users may be excluded or disadvantaged for more than one reason. For example, someone with both poor vision and restricted movement may be identified twice as being excluded by products requiring high vision and movement capability. Consequently, such double/multiple counting of individuals' combined/multiple capability losses need to be corrected for.