Abstract. Current mobile interfaces have numerous usability problems, especially when used by older adults, population of users diverse in ranges and combinations of dis(abilities). However, user interfaces need to be usable by all users, including older adults and disabled people. Universal design (UD), Design for Aging (DfA), and Universal Usability (UU) consider designing systems and interfaces usable by all people, to the greatest extent possible. Set of more inclusive UD guidelines emerged from this integration of the three approaches with mobile design guidelines in order to address usability of user interfaces by diverse population of older adults. An example of an application of the inclusive UD guidelines was universally designed interactive voting interface, EZ Ballot, designed to improve usability of voting systems for older adults. This paper presents the results of the usability testing of the voting system with young and older adults, and reports equal usability of the ballot for both age groups.