# Gazing Characteristics of a Driver during Vehicle Backing
## 4 Discussion  
For the start phase, when drivers drove a vehicle without a backup camera, the average gazing time of the left-side mirror was the longest (NT-V: 5.57 s, S-V: 5.49 s) among the AOIs, as presented in Table 1. The results indicate that drivers mainly used the left-side mirror to check the location of the parking area in this experimental setup. When drivers drove vehicles equipped with a backup camera, the average gazing time of the left-side mirror was the longest (BC-V: 3.37 s, BCS-V: 3.85 s), followed by that of the monitor (BC-V: 2.89 s, BCS-V: 2.15 s). In the vehicles equipped with a backup camera, the drivers mainly used the left-side mirror in addition to the monitor while approaching the parking area. This implies that the left-side mirror might be more efficient in identifying the location of the parking area compared with the monitor when the driver is moving the vehicle backward in a tilted angle. Conventionally, when a driver recognizes a parking area while approaching, for example, a vehicle parked next to the parking area can be a good marker. Here, the image reflected on the left-side mirror and the monitor was investigated using an orange-colored pole as a marker instead of a vehicle parked next to the parking area to avoid impact between vehicles. When a vehicle stopped to change from forward to backward motion, as shown in Figure 8 ai, the left-side mirror reflected the pole and vehicle body side. The driver could grasp the approximate distance between the pole and vehicle body side, as shown in Figure 8 ai. However, the monitor reflected the pole but not the vehicle body side, as shown in Figure 8 aii, where the driver could not grasp the approximate distance between them. When the backing vehicle was at the entry edge of the parking area, as shown in Figure 8 bi, the left-side mirror still reflected the pole and vehicle body side as shown in Figure 8 bi. However, the monitor did not reflect both, as shown in Figure 8 biii. This is considered to be a result of the increase in the gazing time of the left-side mirror, even though the vehicle had a monitor. For the stop phase, when drivers drove a vehicle without a backup camera, the average gazing time of the right-side mirror was the longest (NT-V: 5.06 s, S-V: 4.57 s), followed by that of the left-side mirror (NT-V: 2.32 s, S-V: 2.54 s) as presented in Table 1. This is possibly because the right-side mirror was located closer to a driver seated on the right-hand side of the test vehicle. When drivers drove vehicles with a backup camera, the average gazing time of the monitor was the longest (BC-V: 9.70 s, BCS-V: 8.44 s), followed by the right-side mirror (BC-V: 2.32 s, BCS-V: 2.13 s). In the parking area, the driver is more likely to perform backing by looking at the monitor rather than at the right-side mirror because the driver can see a sufficient area straight behind the vehicle, as shown in Figure 9. The Tokyo Metropolitan Public Corporation for Road Improvement and Management (TMPC) investigated the features of actual traffic accidents in parking lots in Japan. They pointed out that during backing maneuvers under the 90-degree reverse parking system, the crossing of a moving vehicle and a pedestrian's trajectories in a parking lot caused accidents [33]. By using the monitor while backing a vehicle, the driver can easily notice a pedestrian walking through just behind the vehicle in the parking area. The backup camera can be very effective in preventing such collision accidents involving pedestrians during vehicle backing maneuvers. Figure 8: Examples of (**i**) vehicle location, (**ii**) rear views with left-side mirror, and (**iii**) monitor (* D: Distance between the pole and vehicle body side): (**a**) When a vehicle stopped to change from forward to backward motion; (**b**) When a backing vehicle was at the entry edge of the parking area. Figure 9: View through the monitor of the test vehicle in a parking area. In this study, we investigated the time spent looking at the mirrors and rearview monitor during vehicle reversal.