On different lanes: A cross-case analysis of urban experimentation for autonomous driving

Autonomous vehicles (AVs) are considered a promising element in the sustainable transformation of urban mobility systems. Yet, their potential impact and benefit is highly dependent on how they are integrated into existing infrastructures. This paper explores urban experimentation shaping the development and governance of AVs by analyzing two empirical cases in Germany: Hamburg and Karlsruhe. We highlight the role and interplay of visions and expectations in guiding experimentation and governance processes of socio-technical transitions. Based on expert interviews, (urban) mobility strategies, and project insights, we examine how stakeholder expectations and overarching visions mutually influence experimental designs, outcomes, and learning processes. The comparative analysis uncovers two distinct approaches: In Hamburg, experimentation is embedded in a strong vision-related configuration anchored in its Digital Mobility Strategy, aiming for long-term scalability and predefined public-transport goals; Karlsruhe adopts a more expectation-centered approach focused on research-driven and incremental socio-technological advances conceived more generally. By examining how such different future orientations are linked in each case and how they shape experimentation, the paper extends existing perspectives on governing transition pathways. We emphasize the role of temporal dynamics of future orientations as they are enacted, adjusted, and stabilized through experimental practices, alongside institutional arrangements and policy instruments.