Sonar sensor systems have been developed to prevent collisions between vehicles
and surrounding objects by employing ultrasonic sensors mounted at the front of
the vehicle. These systems warn drivers when nearby obstacles are detected.
However, relatively few studies have examined the capacity of sonar to detect
humans. This study aims to clarify the human detection capacity of front sonar
sensors installed in two light passenger cars (LPC-I and LPC-II), one small
passenger car (SPC), and one minivan (MNV). The LPC-I, SPC, and MNV were
equipped with center and corner sensors, whereas the LPC-II had only corner
sensors. Three volunteers—a child, an adult female, and an adult
male—participated in the study. Human detectability was assessed using the
“maximum detection distance ratio,” defined as the ratio of the maximum
detection distance for a volunteer to that for a standard pipe. The results
showed that both the center and corner sensors consistently detected front- and
side-facing human volunteers. For front-facing human volunteers, the maximum
detection distance ratios relative to the pipe were 99–101% (child), 93–101%
(adult female), and 98–101% (adult male) for the center sonar sensor, and
99–102%, 94–102%, and 96–100% for the corner sensor. For side-facing human
volunteers, the corresponding ratios were 97–100%, 92–97%, and 94–99% for the
center sensor, and 95–99%, 91–98%, and 93–98% for the corner sensor. These
detection ratios were closely aligned with those of the pipe. These findings
suggest that front sonar sensors can effectively detect humans prior to vehicle
motion initiation, indicating their potential to reduce low-speed vehicle
collisions with nearby pedestrians.