# Shared eHMI: Bridging Human-Machine Understanding in Autonomous Wheelchair Navigation
## 4 Results and Discussion
### Discussion
#### 4.3.5 Concern and Potential Evaluation of the System  
The results of users' attitude questionnaire reveal that most participants favored autonomous wheelchairs with projection interaction. However, Question 6 indicates that a subset of participants strongly perceived technological risks, leading to distrust and aversion, and showing reservations about the interaction method, possibly avoiding the product. Data analysis indicated a correlation between lower SUS scores and negative attitudes towards the technology. Some participants' unfamiliarity with autonomous driving technology, and others' heightened concerns about potential risks that rely on technological advancements for resolution, influenced their perception of insufficient reliability and safety in the interaction. Additionally, from our interview analysis, we also identified several internal concerns:  
1. Visibility of projections and operating environment: Experienced wheelchair users often anticipate challenges new products might bring. Some participants noted insufficient visibility of projections in bright light conditions and expected improved performance at night or indoor environments. They also expressed concerns about the effectiveness of projections on certain terrains and compatibility with existing accessibility infrastructure. Some believed that on-ground projections might be hard to recognize by passing vehicles, leading to navigation difficulties and unsafe situations due to blind spots.
2. Safety risks: In practical use, the safety of projections and potential distraction issues are of concern. The performance of wheelchairs in densely populated areas and their capability to handle challenging terrains, like steps or uneven surfaces, became crucial topics for discussion regarding safety and trust. Users prioritized safety and preferred to maintain control at any time. During autonomous driving, there is a worry that constantly looking down at projections or getting distracted by other tasks might lead to overlooking environmental risks.
3. Intrusiveness of projections and user image: Wheelchair users often view their wheelchair as an extension of their body and connected to their self-image. How they interact with the outside world affects their self-perception and how others perceive them, and it is vital to avoid drawing extra attention to the user's disability [44; 52; 75]. We considered non-intrusive interaction methods, such as timely appearance and disappearance of interface components and customizable projection switches, to minimize environmental space occupation while still attracting attention in emergencies. Some participants still reported that projections have attracted some attention, and adding auditory cues might cause stress due to excessive focus on the user. In fact, the use of projections in autonomous mode, compared to traditional interaction methods in manual mode, is conspicuous, and the issue of pedestrians overlooking them leading to collision risks must be addressed. Considering the addition of other modalities to build polite and friendly communication is important.
4. Potential applications: Some participants suggested innovative ideas, emphasizing broader applications of the system beyond its primary purpose. In vast environments like parks or large shopping centers, the feature can serve not only wheelchair users but also the general public as a navigational tool. Projected navigation paths on the ground clearly indicate directions, are easy to follow, and are particularly suitable for use in spacious, open spaces. Additionally, in hospitals or elderly care, the potential of using shared eHMI in autonomous wheelchairs is particularly evident. Medical practitioners can preset designated routes, allowing these wheelchairs to project their intentions during transit, helping pedestrians understand and cooperate to reduce collisions, and ultimately assisting patients or the elderly to navigate safely to specific locations within the facility.