Designing touchpad user-interfaces for vehicles: which tasks are most suitable?

Designers of in-vehicle computing systems must consider which input devices are most suitable for use in the safety-critical driving situation. This paper describes a study aiming to establish which tasks are best supported by an in-vehicle touchpad system. Eighteen participants (50:50 right/left handed) drove three routes in a right-hand drive simulator while following a lead vehicle at a perceived safe distance. At specific points, participants were asked to carry out seven tasks of varying qualities using a prototype touchpad system, a touchscreen or a rotary controller interface. Results indicated that participants were most negative (in terms of preferences and performance) with the rotary controller interface. Conversely, the results for the touchpad versus the touchscreen interfaces were clearly task dependent. For instance, with the touchpad, subjective opinions and objective performance were most positive for tasks in which simple commands enabled drivers to bypass the need for complex menu interactions (e.g. changing the interior temperature). In contrast, results for the touchscreen were evidently superior for simple menu selection tasks (e.g. selecting a preset radio station). Conclusions are drawn regarding the nature of tasks that are best suited to alternative input devices within vehicles and the potential for a touchpad/touchscreen solution.