Automated vehicles (AVs) are often part of the vision for sustainable urban futures. By reducing congestion, cutting emissions, and improving accessibility, shared AVs (SAVs) in particular promise to deliver large societal benefits. They could reduce car ownership, free up urban space, and make transport more inclusive. Yet, despite these prospects, people remain hesitant. Public resistance is not merely about resistance to change but also about deeper concerns: trust in automation, the loss of control, unease with sharing rides with strangers, and the disruption of long-established mobility habits. This tension between potential societal gains and individual reluctance lies at the heart of the thesis. To understand this resistance and acceptance, researchers have typically turned to technology acceptance models, most prominently the Unified Theory of Acceptance and Use of Technology (UTAUT). These frameworks have been instrumental in explaining uptake of digital tools and consumer technologies. They are, however, ill-suited for SAVs. UTAUT and similar models have grown very complex and lack situational fit to mobility uptake. In the context of SAVs, the issue is not just whether the technology works, but whether people trust it to carry them safely, whether they feel comfortable sharing intimate space with others, and whether it fits their everyday travel practices.
This thesis thus seeks to enhance understanding of acceptance of SAVs. Three research questions guide this endeavor:
• RQ1: Which psychological and social constructs are necessary and sufficient for acceptance?
• RQ2: How do users experience SAVs in real-world pilots?
• RQ3: Which strategies may enhance acceptance?
These questions are directed at central gaps in the research literature. The vast technology acceptance frameworks dominating the field may be simplified and adapted to the SAV context. Most contemporary research also relies on hypothetical scenarios and survey research, limiting the ecological validity of research. Last, little is known about the mechanisms that shape acceptance.
The thesis includes five papers. The first four rely on survey data while the fifth analyzes qualitative interviews. Paper 1 examined public acceptance of a suburban SAV pilot in Ski, Norway, where a small shuttle operated with a safety driver present. Two cross-sectional surveys were conducted with local residents at the beginning and end of the pilot (N=922 and N=608), capturing perceptions of trust, optimism, and willingness to share rides. Paper 2 tested items from UTAUT and MAVA to find room for simplification in measurement of SAV acceptance. It used a national online survey (N=1902), with a split-sample design to conduct exploratory and confirmatory factor analyses. Paper 3 relied on the same dataset but investigated personality measures (Five Factor Model and Social Dominance Orientation). It also introduced a vignette experiment varying driver presence, seat orientation, and passenger ethnicity, to assess whether informational framing could influence acceptance. Paper 4 was performed as a registered report that introduced and tested the SAVA model in a Norwegian cross-sectional survey (N=1250). A second vignette experiment was embedded. Finally, Paper 5 used twelve semi-structured interviews with early users of Ruter’s SAV pilot in Oslo’s Groruddalen. It used thematic analysis to explore how people perceived one of the first applications of SAVs in a public transport setting.
Results across the five papers suggest that acceptance of SAVs can be parsimoniously conceptualized as comprising trust, perceived utility, and social comfort, although these factors manifest differently across contexts and methods. Paper 1 showed that mere exposure to an early SAV pilot did not increase optimism or trust. Demographic differences, such as gender and age, operated indirectly through these constructs, highlighting trust as a decisive acceptance factor. Paper 2 demonstrated that acceptance can be captured parsimoniously. A large set of items was reduced to a General Acceptance Factor (GAF), with trust and perceived usefulness alone explaining most of the variance in intention to use. Additional dimensions, such as interpersonal security and sociability, added nuance where the social dynamics of sharing were salient. Paper 3 extended this framework by examining individual differences. Personality traits such as openness and agreeableness predicted higher acceptance, while social dominance orientation and neuroticism were linked to lower acceptance. The vignette experiment, however, found no meaningful effects of framing, suggesting that light informational cues are insufficient to shift attitudes. Paper 4 consolidated these insights in the preregistered SAVA model. Structural equation modeling confirmed that trust, utility, and social comfort are both necessary and sufficient predictors of intention to use. Yet again, framing manipulations had no practical effect, reinforcing the limited power of survey-based interventions. Paper 5 turned to lived experience. Interviews with early SAV users revealed that acceptance depended not only on abstract evaluations but on whether services could be integrated into their everyday mobility practices. Trust was tied to vehicle behavior and institutional legitimacy, utility to meeting local travel needs, and social comfort to the norms and interactions inside the vehicle.
Viewed as a whole, the five studies show that acceptance of SAVs can be accurately measured using a parsimonious framework. The thesis shows the value of including real users of SAV services, as they provide nuanced knowledge. It also shows that, while difficult to manipulate in surveys, several characteristics of SAVs and its users may be key in determining acceptance. Theoretically, the thesis demonstrates that large and intricate frameworks such as UTAUT are not well suited to the SAV context. The proliferation of constructs may obscure rather than clarify the mechanisms of acceptance. By contrast, the SAVA model provides a more focused account, showing that a small set of factors is both necessary and sufficient to explain intention to use. At the same time, the thesis highlights that acceptance cannot be reduced to cognitive evaluations alone. The qualitative interviews show how trust, utility, and comfort are lived and negotiated through practices, identities, and mobility needs. This underscores the importance of situating research in the appropriate context. Early pilots do not automatically build trust or optimism. In fact, perceptions may be less malleable than previously assumed. This suggests that exposure alone is not enough, particularly when the technology is deemed immature. Light vignette interventions appear insufficient to overcome hesitations tied to trust, utility, and social dynamics. Instead, interventions may need to be embedded in service design and real-world experience to be effective. The results point to clear levers for increasing acceptance. Building and maintaining trust requires not only reliable technology but also transparent communication and credible institutions. Utility depends on whether SAVs meet everyday mobility needs rather than abstract promises of sustainability. Social comfort hinges on the design of the service, and on fostering an inclusive environment that counteracts the norm vacuum of this novel mode of transport.
In sum, the thesis clarifies the core conditions of SAV acceptance, demonstrates the limits of abstract survey approaches, and shows how acceptance is rooted in everyday practices. By combining parsimony at the level of constructs with richness at the level of lived experience, it refines theory while offering policymakers and practitioners concrete pathways for making SAVs a credible part of sustainable mobility futures.