## 4 Discussion
### Recommendations for Future On-Board Operator Workspace Design
#### 4.2.1 Workspace Design  
This section provides recommendations for on-board operator workspace design, structured according to the WDQ subscales. Regarding the operator feedback that falls under the subscale on _ergonomics_, it can be concluded that the different body heights of operators need to be considered. It is essential to enable individual adjustments of seating positions, as well as the location and viewing angle of screens and input devices. Screens that need to be attended during the ride should face in the direction of the driving trajectory, providing operators with critical information without taking their eyes off the road. Such a placement minimizes distractions and contributes to safer operation. If a seat is added for the on-board operator's safety and comfort, its height should be adjustable. This is to provide a better overview of the surroundings in order to enhance the operator's field of view and reduce blind spots, e.g., right in front of the vehicle. In order to not accidentally hit buttons, as was reported for the emergency button in one of the presented shuttles, it should be checked that operators can move freely without hitting any control elements by mistake. Buttons should be made readily accessible and easy to reach in case of unforeseen situations or emergencies. The placement of buttons should always be task-related. This means that a button's position is a consequence of the task or workflow it is a part of. For example, a button to give clearance to driving maneuvers should be placed in the direction that needs to be checked in order to do so. In general, it is strongly advised that the guidelines on ergonomic work design [36] and human-centered design [37] are followed. When it comes to the _physical demands_ imposed on the operator, a central point is the permanent standing that was required to monitor the traffic surrounding the shuttle vehicle. An ergonomically sound and individually adjustable seat, comparable to that of a regular bus driver, combats posture problems, thus preventing neck and back pain. A positive side effect would be that longer shifts might be possible this way. If a fixed seating position was established, the placement of control units and displays could be oriented toward the operator, preventing posture issues that result from leaning forward or to the side to view or operate HMI elements, or from carrying a control unit around one's neck (as in RealLabHH and TaBuLa). Regarding _equipment use_, it took operators quite some time to understand and be able to use the operating systems. A factor to consider might be the transparency of the system. The HMI should make the system's state, as well as the system's decisions and reasons for decisions, evident to the operator. A lack of system transparency was reported in HEAT and RealLabHH. Both living labs yielded below-average ratings by operators. In addition to transparency, adequate training is important to enable the operators to interact smoothly with the vehicle via the HMI. It is advisable that both routine use cases and edge cases are incorporated into the operator training, in order to prepare the operator for safe and effective HMI use in as many situations as possible. Finally, conducive _work conditions_ are essential for effective task performance. In addition to manageable shift lengths, regular breaks, and reliable support by coworkers, this also includes aspects of communication to third parties. An example is operators being kept in the loop when it comes to feedback they provide, e.g., on incidents regarding malfunctions with the automation. Particularly in living labs that depend on continuous feedback to improve vehicle automation and operational workflow, on-board operators should be kept in the loop regarding the impact that their feedback has in the optimization process. As the operation of a shuttle vehicle is a complex sociotechnical system, all actors and components in the system have to be carefully analyzed regarding their interactions and the way they collaborate.