This study aims to propose a movable in-vehicle convenience device system for Level 4–5 autonomous driving contexts—where the cabin shifts from a “driving-centered” space to an “occupant-centered living space”—and to empirically evaluate both its overall usability and the effectiveness of using physical motion itself as an alert modality. Building on a previously developed console-type device and a rail-based bracket mechanism, the authors integrated these elements into a unified system in which the device can translate laterally and rotate in place while inside the vehicle, and can also be detached via vertical lifting from the rail structure so that it can be used outside the vehicle as an independent product. By enabling occupants to reconfigure the space while engaging in non-driving activities such as working, resting, dining, and entertainment, the system embodies the concept of “experience continuity,” extending convenience benefits formed in the vehicle to the destination environment through physical portability and re-deployability.

The evaluation was conducted in two stages with the same 24 participants. In the first experiment, overall usability and acceptance were assessed using the System Usability Scale (SUS) and in-depth interviews. The mean SUS score was 76.04, indicating an “acceptable” level of usability. Item-level responses suggested that participants generally perceived the system as intuitive and operable without extensive learning; however, the item corresponding to reuse intention (“I would like to use this frequently”) was relatively lower, implying that design must not only demonstrate functional feasibility but also convincingly motivate sustained, everyday use. Regarding preferences by function, rotation received the highest positive evaluation (75.0%), followed by translation (54.2%) and detachment (45.8%). Rotation was favored because its role as a table-like function felt clear and immediately useful, yet participants also expressed concerns about practicality and hygiene due to potential shaking while the vehicle is moving. Translation was valued for enabling object delivery without requiring occupants to physically move, highlighting potential safety and convenience benefits, although some questioned whether it would be necessary in situations where direct handoff might be faster. Detachment was positively viewed for enabling outdoor use and extending the experience beyond the vehicle, but participants repeatedly raised cleanliness issues—such as contaminants being brought back into the cabin—and pragmatic doubts about whether people would actually carry the device outside. In terms of actuation style, participants most preferred a hybrid approach combining automatic and manual control. Translation in particular showed a stronger preference for manual control because unexpected automatic motion could feel uncomfortable or risky, and both detachment and rotation also benefited from user-driven initiation or fine adjustment. Overall, the findings indicate the need to differentiate the level of automation by function rather than applying uniform automation across all movements.

The second experiment examined whether the device’s physical motion can function as a pre-alert that captures attention more effectively than conventional display-based color alerts. The study used a within-subject design of 2 (alert type: physical motion vs. color) × 3 (scenario: motion toward the occupant, motion away from the occupant, and detachment). Tobii-based eye tracking measured attention responses through interval duration, total fixation duration, and fixation count, while post-task interviews and questionnaires captured which alert participants believed they noticed first and which they preferred, allowing comparison between subjective judgments and objective measures. The results showed that physical-motion alerts significantly increased fixation counts compared to color alerts (M=4.17 vs. 3.15), suggesting an advantage in repeatedly drawing attention; however, differences in total attention time were not as pronounced, implying that the key effect lies less in “how long people look” and more in “how often they re-check.” Scenario effects were also observed: the detachment scenario produced significantly higher fixation counts than motion toward the occupant, and motion away from the occupant was also higher than motion toward the occupant, indicating that different movement types can demand different levels of repeated visual verification.

An important contribution of this study is its evidence that objective attention effects and subjective judgments do not always align. While physical motion may be advantageous for unconscious attention capture, especially in relatively simple translation scenarios participants’ self-reports about what they noticed first or what felt clearer sometimes diverged from eye-tracking data. This suggests that alert design should not simply standardize on a single “stronger” stimulus, but should instead select and combine modalities in a context-sensitive way, considering scenario complexity, potential risk, and the occupant’s level of task immersion. In sum, the study proposes a concrete mobility mechanism for in-vehicle convenience devices that supports space reconfiguration and experience continuity, verifies an acceptable level of usability while clarifying function-specific perceived value and concerns, and demonstrates that physical motion can be effective for repeated attention prompting while also highlighting possible gaps between perceived clarity and measured attention. The authors conclude that alerts should be designed against dual criteria—attention capture and cognitive clarity—and note that further validation is needed with broader scenarios, more diverse user groups, and conditions closer to real driving environments, with future work focusing on finer-grained non-driving activity contexts and corresponding device types and alert strategies.