The tactile sense as a mechanism for the reduction of visual load elicited by control interactions : an automotive case study approach to the development of generic design recommendations

This thesis examines the potential for using tactile feedback to reduce the visual load that can be associated with interacting with controls. Using the automotive context as a case study, the thesis describes the process followed in the design of a prototype tactile interface (PTI) for the control of in-car secondary functionality (navigation, entertainment and climate control). There have been many examples of the use of active and passive tactile feedback to provide information to visually impaired people. There is however a paucity of previous research into the field of tactile feedback in mainstream product design. A literature review was performed examining various issues that are associated with tactile design including cognitive processing of tactile inputs, the use oftactile feedback in products used by visually impaired people and standard control design recommendations. This was followed by the generation of initial concepts and the first study, which examined how visually impaired people interact with electronic products that are unfamiliar to them, and also examined how they used their own equipment. The results from this study, and the literature review findings were combined into a series of design recommendations for the production of tactile interfaces that aim to reduce the visual load on the driver. These design recommendations were the basis for an iterative design process that resulted in the first, non functioning PTI interface model. The first PTI was constructed using rapid prototype technologies. The first iteration PTI was examined in the second study, a user trial in a driving simulator. The study produced encouraging results with a >90% success rate for correct control selection without vision, whilst performing a driving task. The results from this study were used to refine the design of the PTI and a working, hi-fidelity prototype was constructed for use in the final study. This study involved 'on the road' user trials comparing the glance durations made to the PTI and to a baseline system using a 'repeated measures' structure. The data from these user trials were examined to determine if the PTI exhibited a reduced visual load when compared to the baseline system. The results showed the PTI fostered significantly reduced summed glance durations for 7 of the 11 tasks performed when compared to the baseline system. Three of the 11 tasks that were performed in the study produced a reduction of summed glance duration of >50%. The PTI was also shown to foster non-visual interaction, with all participants performing at least one control interaction without looking at the control arrays. The tactile coding and symbolic layout of the PTI have been shown to be beneficial in terms of reducing 'eyes off road time' and therefore reducing the risk of distraction related accidents. A review of the results from the three studies described in this thesis has enabled the development of generic design guidelines for the production of tactile interfaces where a reduction in visual load is required for the safety of the operator. The thesis has made a contribution to the understanding of the use of the tactile sense during product interactions, and highlighting the benefits as well as the limitations of the tactile sense as a feedback mechanism.