抄録
To develop a driving environment for people with spinal cord injury that reduces their physical burden while they drive a car, a preliminary study was conducted to examine the acceleration of the head while driving, using a 3D motion analysis system. The subjects were five males with spinal cord injury. The mean age was 39.0 years old, and the level of spinal cord injury was C5 or C6. They usually used manual wheelchairs to move around. In the experiment, the vehicles owned by the individual subjects and the commercial driving assistance devices were used. The driving course included five left- and right-curve segments each. The subjects were asked to drive at 10, 20, 30, and 40 km/h in random order. A marker was attached to the left ear of the subjects, and their heads while driving were recorded using two video cameras. A 3D motion analysis system was used, and the position, speed, and acceleration of the marker attached to the head were calculated. There were no significant differences in the acceleration of the head when the subjects drove on either left- or right-curved segments at 10 to 30 km/h. When the subjects drove at 40 km/h, the accelerations in the left-right and front-back directions on the left-curved segments were 2.6 and 2.5 m/s2, respectively. The accelerations in the left-right and front-back directions in the right-curved segments were 3.1 and 3.2 m/s2, respectively; there were significant differences in the acceleration in the front-back direction (p < 0.05). There were also significant differences in the acceleration of the head in the front-back direction immediately after the subjects entered left and right curves (p < 0.05). When the car was driven at 10 to 30 km/h, there was no significant difference in the acceleration of the head between the left- and right-curved segments. However, when the subjects drove at 40 km/h, the acceleration of the head on the left-curved segments was higher than that on the right-curved segments, in the front-back direction in particular. This suggests that, when vehicles curve to the right at 40 km/h, the acceleration is faster and the net force applied to the head is greater than when they curve to the left. Our previous study (2010) suggested that, when vehicles curve to the left at a fast speed, the change in the position of the head is greater than when they curve to the right. The results of our previous and present studies suggest that, to assess the burden placed on the body while driving, it is necessary to not only examine changes in the position of the head, but also determine the acceleration of the head as an assessment index.
