Exploring the Usability of Vending Machines through Multi-Method Evaluation Techniques

Usability is a key quality attribute to ensure accessibility and high user acceptance of any embedded system. While several studies have examined the usability of embedded systems, only a few have specifically addressed the usability assessment and intuitive design of systems like vending machines. Therefore, the objectives of this research are to explore the usability of existing vending machines and to propose design solutions for enhancing the usability of such embedded systems. To achieve these objectives, three unique vending machines (Your Shop, SnacKeeper, and SPN Convenience) were evaluated using both Heuristic Evaluation (HE) and Cognitive Walkthrough (CW) methods; and revealed a wide range of usability problems. A comparative analysis was performed between the findings of both methods and then the identified usability issues were categorized into interface accessibility, transactional design, instructional layout, and visibility & clarity. Based on the findings, a set of design recommendations was developed to address these challenges. Additionally, as an example a prototypical design was created based on the proposed recommendations. As such, the findings of this study will make a substantial contribution to the fields of embedded system design and human-computer interaction (HCI) to offer valuable insights for designing more usable and intuitive vending machines.