# Gazing Characteristics of a Driver during Vehicle Backing
## 1 Introduction
Several researchers employed the eye tracker technology to follow the eye movements of a driver for understanding his/her behavioral characteristics while driving [18; 19; 20; 21; 22; 23; 24]. [PERSON] et al. assessed the feasibility of measuring drivers' automation trust via gaze behavior during highly automated driving with eye tracking using a simulator and concluded a negative relationship between the driver's self-reported automation trust and monitoring frequency [25]. Using an eye tracker, the effectiveness of a head-up display to increase the safety performance for vehicle-to-vehicle, vehicle-to-pedestrian, and vehicle-to-bicycle was investigated using a simulator in which the head-up display can provide information on the distance between the host vehicle and other road users by changing color [26]. [PERSON] et al. designed an in-vehicle eco-safe driving system and confirmed that the eco-safe human-machine interface system did not cause visual distraction during driving in a simulator study focusing on the driver's glance behavior [27]. [PERSON] et al. examined the effects of visual distractions during driving using a driving simulator and showed that when the visual task is presented centrally, the driver's lane deviation decreases [28]. Although many researchers have investigated the driver's gaze when driving a vehicle in the forward direction, the features of the driver's gaze during backing remain unclear. When a driver parks a vehicle, the driver can see the parking area by direct vision during forward parking and by indirect vision during reverse parking. The objective of this study was to elucidate the effect of vehicle safety technology on a driver's gaze characteristics during backing vehicle maneuvers. Most vehicle parking in the urban areas of Japan employs the 90-degree reverse parking system, which utilizes the highest space efficiency owing to the limited size of land [29]. An example of vehicles parked in reverse in Japan is shown in Figure 1. In the 90-degree reverse parking system, the vehicle initially moves forward with a slight right turn and then stops (Figure 1a); then, it restarts backing rearward until it stops in the parking area (Figure 1b). In the present study, we focused on the driver's gaze while the vehicle is backing rearward (Figure 1b) using a test vehicle. For vehicles not equipped with a rear camera, it is unclear what the driver is looking at through the rearview mirror. Even when a rear camera is installed, it is unclear how long the driver uses the monitor, if at all, and whether they are also using the conventional rearview mirror. In other words, if there is a monitor in the cabin of a vehicle, it is unclear whether the driver needs conventional rearview mirrors during backing. Therefore, in the present study, we conducted an experiment using a real vehicle to clarify which mirrors drivers use, and for how long they use them, during vehicle reversal. Similarly, in the case of a vehicle with a rear camera, we investigated how long drivers spend looking at the dashboard monitor. These outcomes will offer basic information to understand a driver's psychology and influence the design of vehicles and parking areas. In the present study, we investigated the features of the driver's gaze while backing using an eye tracker. We employed four conditions for vehicle safety technology: no-tech vehicle (NT-V), sonar vehicle (S-V), backup-camera vehicle (BC-V), and backup camera with sonar vehicle (BCS-V).