# A Study on Ergonomic Layout of Automotive Electronic Shift Buttons
## 1 Introduction  
Automotive transmissions, which are used to shift between park (P), reverse (R), neutral (N), and drive (D) for longitudinal vehicle control, are among the most important control devices for driving [1]. In 1965, the American Society of Automotive Engineers (SAE) established an international standard requiring car manufacturers to design gear shifters according to the manual control sequence P-R-N-D [2]. This standard was intended to reduce accidents caused by driver confusion and erroneous operations, which occurred frequently mainly because the arrangement and order of gear positions (hereafter, referred to as layout) previously differed for each car manufacturer/model. The Code of Federal Regulations (CFR), title 49 (transportation), stipulates the following [3]:  
\"S3.1.1 Location of transmission shift positions on passenger cars. The N position is to be located between the D and R positions.\"  
\"S3.1.1.1 Transmission shift levers. If a steering-column-mounted transmission shift lever is used, the movement from the N position to the D position is to be clockwise. If the transmission shift lever sequence includes a P position, it is to be located at the end adjacent to the R position.\"The recent advances in automotive transmissions have enabled various advantages in shift-by-wire (SBW) systems. As a result, they have replaced the conventional mechanical transmission system [4; 5], and they have become customary over the last several decades. The SBW systems not only possess several advantages in terms of driver convenience and ease of gear shift operation, but they also help improve the level of freedom in transmission system design and space utilization inside vehicles [5; 6; 7]. In particular, an SBW system with electronic shift buttons facilitates easier gear shifting as compared with a transmission shift lever [8]. Moreover, there is no restriction on the mounting position of the gear shifter, and thus the internal space of the vehicle can be effectively utilized. Furthermore, in the event of an accident, no collision can occur between the body of the passenger and the gear shifter, thereby preventing injury to the passenger [6]. Despite these advantages, SBW systems with electronic shift buttons are not within the scope of the aforementioned SAE/CFR international standard. Therefore, there are no minimum requirements or regulations for the electronic shift button layouts. In addition to this, there are no detailed regulations related to various design factors such as the shift button size, color, separation, and visual/tactile feedback. Accordingly, as shown in Table 1, various layouts have been adopted by different car manufacturers/models, and this introduces the risk of erroneous operation by drivers. [PERSON] et al. [9] demonstrated that ill-structured console layouts result in an increase in the operator workload and subsequently increase the task completion time and error rate. The electronic shift button layout determines the accuracy, convenience, and speed of gear shifting, and it may affect the driving performance and overall safety [10]. Even though erroneous operation and safety accidents have occurred due to ill-structured shift button layouts and vehicles have been recalled accordingly [11; 12], and standardization efforts and studies of ergonomic performance of electronic shift button layouts have not been actively performed. Given that electronic shift buttons are key elements in longitudinal vehicle control, a well-designed button layout is particularly important from an ergonomic perspective [13]. Accordingly, it is necessary to determine ergonomic electronic shift button layouts to improve the driving performance and reduce erroneous operation. Therefore, as an effort toward the ergonomic design of automotive electronic shift button layouts and its global standardization, we investigated the ergonomic performance of different shift button layouts.