Co-Designing the Sound of Safety: Embracing Complexity in the Acoustic Vehicle Alerting System Sound for Zero Emission Buses

Around the world, transport organizations are transitioning their bus fleets from internal combustion engines to electrified zero emission buses (ZEBs). The quiet nature of these buses raises safety concerns for vulnerable road users. To address these concerns, new standards mandate that electric vehicles, including ZEBs, be equipped with an acoustic vehicle alerting system (AVAS) emitting sound at low speeds, to make vehicles more detectable. However, developing an effective AVAS sound requires balancing safety and technical constraints with diverse stakeholder needs. Using codesign, this study conducted a series of risk-focused subject matter expertize workshops (n = 15), and a large user-experience focused participatory design workshop (n = 41) to inform the AVAS sound design. The latter included empathy and user journey mapping techniques, facilitating the collection of insights from various perspectives. Results revealed stakeholder preferences for an AVAS sound that was both alerting and positive, and embodied qualities like calmness, politeness, and vibrancy. The workshops allowed for refinement of sound design requirements, although challenges emerged in balancing conflicting preferences and managing technical limitations to create a sound that could be both perceptible and nonintrusive. This study provides a framework for the development of an AVAS sound that could capture a range of stakeholder needs and preferences and lays a foundation for AVAS sounds that enhance safety while being positively received. It highlights the importance of inclusive, iterative design in advancing public transport safety and sustainability, with outcomes supporting the future sound design, testing, and implementation.