# A Study on Ergonomic Layout of Automotive Electronic Shift Buttons
## 4 Discussion
In addition, it is expected to contribute to the international standardization of electronic shift button layouts. Second, the study results could be practically applied not only to automotive transmission systems, but also to the ergonomic design of control devices with electronic buttons for the operation of machines/tools currently used throughout the industry. They could also be applied to design control devices for future industrial robots and unmanned vehicles. Third, the study results showed that some shift button layouts designed to be the same as or similar to the existing commercialized ones were not found to be superior to others. In a similar vein, the study findings revealed that the sequence of P-R-N-D, which has been dominantly adopted in the conventional lever-type gear shifter, would not necessarily lead to the most excellent sequence in the button-type gear shifter as well, thereby suggesting that some important design characteristics could be changed depending on the type or operation method of the gear shifter. Therefore, the current study indicated that in designing an electronic gear shifter or, more generally, a control device, it would be desirable to comparatively evaluate different alternatives, including novel unexplored designs rather than blindly applying the consistency principle to make a correct design decision. Finally, this study revealed that the compatibility, functional similarity, and stereotype principles were more significant for novice drivers, whereas the consistency principle was more significant for experienced drivers when designing button layouts. In other words, this study empirically demonstrated that the effectiveness and importance/priority of a series of design principles related to control layouts described in the existing ergonomic literature and textbooks can vary depending on the user characteristics, such as the degree of skillfulness, which may help improve the understanding of the design principles further. A few limitations of this study are described below, along with other topics for future research. First, the 12 design alternatives in this study were derived by changing only the layout of the 4 gear shift buttons. Given that there are various design factors other than the button layout, such as the size, color, materials, separation, slope, and visual/tactile feedback of the shift buttons [32], future studies will involve ergonomic design guidelines for each of these factors. Second, although the number of survey respondents in the current study was adequate to allow statistical testing of the mean difference without much concern for statistical power, future studies with a larger sample size would be needed for more accurate study results. Besides such statistical testing of the mean difference, some other mathematical approaches could be applied to the collected data to achieve different meaningful study findings. One possible approach would be using a multiple regression analysis with an ergonomic performance (evaluation score) of a shift button layout as the dependent variable and its constituent design characteristics as the independent variables (predictors). For example, a regression model fitted with predictors indicating whether an ergonomic layout design principle was applied or not could be utilized to predict an ergonomic performance of a novel unexplored shift button layout, and could be used to reveal the relative importance of the four ergonomic layout design principles considered in this study. Third, considering that there is no restriction on the mounting position of the SBW system with electronic shift buttons [6], future studies may consider different in-vehicle positions of the gear shifter (e.g., on the steering wheel, center fascia, or center console) to elucidate the interaction effects between the mounting position and layout.