Supplementary data for the paper 'Should steering settings be changed by the driver or by the vehicle itself?'

<strong>Objective. </strong>This paper aimed to investigate whether steering gain (SG) mode changes should be made by the driver or automatically. <strong>Introduction. </strong>Cars are increasingly computerized, and vehicle settings such as SG can now be altered during driving. However, it is unknown whether transitions in SG should be adaptable (i.e., triggered by driver input) or adaptive (i.e., triggered automatically). We examined this question for road segments expected to require different SG. <strong>Methods.</strong> Twenty-four participants drove under four conditions in a simulator: fixed low gain (FL), fixed high gain (FH), a machine-initiated steering system, which switched between the two SG levels at predetermined locations (MI), and a driver-initiated steering system, in which the SG could be changed by pressing a button on the steering wheel (DI). <strong>Results. </strong>Participants showed poorer lane-keeping and reported higher effort for FH compared to FL on straights, while the opposite held true on curved roads. On curved roads, the MI condition yielded better lane-keeping and lower subjective effort than the DI condition. However, a substantial portion of the drivers gave low preference rankings to the MI concept. <strong>Conclusion. </strong>Drivers prefer and benefit from a steering system with a variable rather than fixed gain. Furthermore, although automatic SG transitions reduce effort, some drivers reject this concept. <strong>Application. </strong>As the state of technology advances, MI transitions are becoming increasingly feasible, but whether drivers would want to delegate their decision-making authority to a machine remains a moot point.

**研究目标**。 本研究旨在探讨转向增益（Steering Gain，SG）模式的切换应当由驾驶员手动执行，还是由系统自动完成。
**研究背景**。 当前汽车的电子化水平持续提升，驾驶过程中可对转向增益（SG）等车辆参数进行动态调整。但目前尚未明确，转向增益的切换应当采用驾驶员输入触发的适配模式（即由驾驶员主动触发），还是系统自动触发的自适应模式。本研究针对预期需要不同转向增益的道路路段，对这一问题展开了探究。
**研究方法**。 本研究招募24名被试，在驾驶模拟器中开展4组实验：固定低增益（Fixed Low Gain，FL）组、固定高增益（Fixed High Gain，FH）组、机器触发式转向系统组（即系统在预设路段于两种转向增益等级间自动切换，Machine-Initiated，MI），以及驾驶员触发式转向系统组（驾驶员可通过方向盘上的按键调整转向增益，Driver-Initiated，DI）。
**实验结果**。 实验结果显示，在直线路段中，固定高增益（FH）组被试的车道保持表现劣于固定低增益（FL）组，且主观操作负荷更高；而在弯道路段则呈现相反趋势。在弯道路段，机器触发式（MI）组的车道保持表现优于驾驶员触发式（DI）组，且主观操作负荷更低。但有相当比例的被试对机器触发式转向系统的偏好程度较低。
**研究结论**。 相较于固定增益转向系统，可变增益转向系统更受驾驶员青睐，且能为驾驶员带来操作收益。此外，尽管自动转向增益切换可降低操作负荷，但部分驾驶员仍排斥该设计方案。
**应用展望**。 随着技术的不断进步，机器触发式转向增益切换的可行性日益提升，但驾驶员是否愿意将驾驶决策权限交由系统完成，仍是一个尚存争议的议题。