Edinburgh Napier University

  Designers instinctively design for able-bodied users and are either unaware of the needs of users with different capabilities, or do not know how to accommodate their needs into the design cycle. Hence, there is an urgent need for design methods, based on a better understanding of age and ability related factors, which will lead to a minimising of the impact of impairments and thereby extend quality life. The aim of this paper is to present a methodological design approach for implementing inclusive design. A summary of the principal methods for designing for users with different capabilities is given along with a description of a model, the Inclusive Design Cube, that displays how the different approaches are complementary and can provide complete population coverage. Building on the concept of the user pyramid design approach (Benktzon, 1993), the authors have developed a model that relates capability level, population profile and suitable design approach in a simple graphical format. The resultant model is the inclusive design cube (IDC) (Keates and Clarkson, 1999). Each axis on the cube represents user capability and the enclosed volumes reflect population coverage. The IDC is a very potent visualisation tool and communicates the needs of different sections of the population. However, for practical implementation of inclusive design practices, it is necessary to have an accompanying rigorous methodology. Developing a usable product interface for wider user capabilities involves understanding the fundamental nature of the interaction. Typical interaction with an interface consists of the user perceiving the output from the product (perception), deciding a course of action (cognition) and the implementing the response (motor function) (Card et al., 1983). These steps relate directly to the user?s sensory, cognitive and motor capabilities respectively. Building on this and Nielsen?s usability heuristics (Nielsen and Mack, 1993), a design approach has been developed, where each level is accompanied by user trial evaluations before progression to the next level. The 7-level approach has been successfully applied to the design of a software interface for the control of an interactive, assistive technology robot (Clarkson et al, 1999) and the evaluation of an information point for use in post offices. The latter shall be presented as a case study to demonstrate how application of the 7-level approach would have affected its overall usability. Using the 7-level approach and the Inclusive Design Cube, serious usability and accessibility shortfalls were identified that are being addressed in the information point re-design.