Developing a methodology for the design of accessible interfaces S. Keates * , P.J. Clarkson * and P. Robinson ** * University of Cambridge, Department of Engineering (CUED), Trumpington Street, Cambridge, CB2 1PZ, United Kingdom Tel +44 1223 332600, Fax +44 1223 332662, E-mail lsk12, pjc10@eng.cam.ac.uk, URL http://rehab-www.eng.cam.ac.uk ** University of Cambridge, Computer Laboratory, New Museums Site, Pembroke Street, Cambridge, CB2 3QG, United Kingdom Tel +44 1223 334637, Fax +44 1223 334678, E-mail Peter.Robinson@cl.cam.ac.uk, URL http://www.cl.cam.ac.uk/users/pr/ Abstract. Users with a number of different motion impairment conditions cannot cope with most current computer access systems. Such conditions include athetoid, ataxic and spastic Cerebral Palsy, Muscular Dystrophy, Friedrich’s Ataxia, tetraplegia and spinal injuries or disorder. Frequent symptoms include tremor, spasm, poor co-ordination, restricted movement, and reduced muscle strength. Similar symptoms are also seen amongst the elderly able-bodied population from conditions such as Parkinson’s Disease, strokes and arthritis. The primary aim of the programme of research at the University of Cambridge is to enable the design of accessible input systems and interfaces for all motion-impaired users, both elderly and disabled. Current interface design practices are based on user models and descriptions derived exclusively from studies of able-bodied users. However, such users are only one point on a wide and varied scale of physical capabilities. This paper will show that there are very important differences between those with motion-impairments, whether elderly or disabled, and able-bodied users when they interact with computers. Without a proper understanding of those differences, interface design will remain an exercise in making the interfaces more comfortable for the motion-impaired users, rather than really usable. This paper describes our experiments to understand how motion-impaired users interact with computers and how we are using this information to develop a methodology for the design of accessible interfaces. 1. INTRODUCTION Computers can be a source of tremendous benefit to those with motion impairments [Busby 97]. They offer greater freedom to participate in education and leisure activities, as well as increased job potential and satisfaction. They also enable employers to retain the services of experienced employees who might otherwise have to retire through ill health and to recruit those with motion-impairments. For example, the ability to operate a word processor, spreadsheet and database is often sufficient to perform many useful administration tasks. Computers are also the basis of modern communications systems. The Internet is a prime example that offers a great opportunity for disabled users [Nelson 94]. The advent of e-mail across millions of networked computers and hybrid mail services can enable dialogue that is entirely independent of the ability to speak clearly, often a difficulty for those with motion- impairments, and eliminates prejudices based on appearances. Home life can be improved through access to on-line facilities such as home shopping.