## 5 Conclusions  
This study derived a total of 15 electronic gearshift design alternatives by combining three operation methods (\(\mathbf{M_{LS}}\), \(\mathbf{M_{BP}}\), and \(\mathbf{M_{DR}}\)) and five in-vehicle locations (\(\mathbf{L_{LWS}}\), \(\mathbf{L_{RWS}}\), \(\mathbf{L_{UCF}}\), \(\mathbf{L_{LCF}}\), and \(\mathbf{L_{CC}}\)). The respondents evaluated each design alternative across nine ergonomic evaluation measures. The results indicated that the best ergonomic operation method, in-vehicle location, and their combination were \(\mathbf{M_{LS}}\) and \(\mathbf{M_{BP}}\), \(\mathbf{L_{LCF}}\) and \(\mathbf{L_{CC}}\), and \(\mathbf{M_{LS}L_{CC}}\), respectively. A summary of the major findings and answers to the three research questions is presented in Table 9.  
This study provides practical and theoretical implications/contributions as follows. First, through the inferior evaluation of \(\mathbf{M_{DR}}\) (**Major finding A**), this study identified its HMI design issues, suggesting the need for a redesign of the \(\mathbf{M_{DR}}\) that has been currently adopted with a uniform design featuring a lateral operation direction and lateral arrangement of gear positions. As a potential design solution for innovation/improvement in the HMI design of \(\mathbf{M_{DR}}\), a longitudinal design of the operation direction and arrangement of gear positions can be proposed, though its effectiveness will need to be investigated in future research. Second, through the superiority of the \(\mathbf{L_{LCF}}\) and \(\mathbf{L_{CC}}\) (**Major findings B-1** and **B-2**), it could be recommended that when designing the location of electronic gearshift, consideration should be firstly given to the existing/traditional ones. Third, the superiority of \(\mathbf{M_{LS}L_{CC}}\) (**Major finding C-1**) confirmed the excellence of the combination of the traditional operation method and the traditional in-vehicle location in designing electronic gearshifts. However, the relative superiority of \(\mathbf{M_{BP}L_{RWS}}\) and \(\mathbf{M_{BP}L_{UCF}}\) (**Major finding C-2**) implies that non-traditional operation methods could be superior when implemented in non-traditional in-vehicle locations, which provides opportunities for HMI design improvement/innovation for electronic gearshifts. Finally, the ergonomic design characteristics of electronic gearshifts derived in this study can serve as design/improvement guidelines to address the frequently reported safety issues associated with using electronic gearshifts. Furthermore, it is anticipated that these guidelines could be applied to the design of the operation method and in-vehicle location of electronic gearshifts for new types or future modes of transportation. The limitations and future research directions of this study are as follows. Firstly, although the number of respondents in this study was sufficient to conduct statistical tests without concerns about statistical power, increasing the sample size would be necessary in future research to ensure more accurate results. In doing so, it can be recommended to recruit an additional group of drivers, beyond the two age groups (young adulthood and middle-aged) and two driving experience groups (novice and experienced) recruited in this study. For instance, an 'older driver group' (aged 70 and above) for age and an 'intermediate driver group' (falling between novice and experienced) for driving experience could be recruited. The inclusion of such additional driver groups may help reveal meaningful differences in the study results among various driver segments. Secondly, since approximately half of the 15 design alternatives derived in this study have never been implemented in practical settings (production car models), the respondents evaluated each design alternative in an illustrated form, relying solely on their imagination of future interactions/experiences with it.