Towards Context-Aware Usability Assessments in Vehicles: Developing the CAUS Scale for Multimodal Interfaces

Modern vehicle infotainment systems are increasingly multimodal, enabling drivers to interact through voice, touch, and gesture.While these input methods enhance usability, most existing tools overlook the dynamic driving context-such as traffic density, road complexity, and cognitive load, leading to incomplete evaluations.This workin-progress introduces the Context-Aware Usability Scale (CAUS), a psychometric instrument for evaluating multimodal in-vehicle interfaces with sensitivity to environmental factors.CAUS is developed through a three-phase process: (1) item generation from a systematic literature review using the PRISMA framework, (2) expert validation via Content Validity Index (CVI) methods, and (3) planned empirical testing in a high-fidelity driving simulator.The 20-item scale spans five core usability dimensions -efficiency, effectiveness, cognitive load, distraction, and satisfaction -and five context-sensitive items.Expert evaluations confirmed strong content validity (S-CVI > 0.90).The final phase will assess reliability and factor structure.CAUS offers an ecologically valid, scalable tool for evaluating automotive HCI, with applications in smart mobility and mobile interface design.