This study aimed to investigate the effects of selective restriction of central vision on the walking speed while descending a standard staircase. An experiment was performed by using a newly developed experimental instrument for restricting the arbitrary area of the human visual field. Subjects descended a short staircase under different visual conditions wearing the experimental instruments. The main result of the experiment was that, in the beginning area that included the first and the second steps of the staircase, the walking speeds under the visual condition that the central vision was selectively restricted were significantly slower than the walking speed under the other visual condition. The results indicated that, for walking fast through the beginning area of the staircase, the central vision has to be intact for receiving certain specific visual information from the environment.

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Kecskemethy et al showed that they can estimate the minute joint angle and joint displacement in the elbow joint from a pro-/supination angle by identifying three stiffness parameters of the forearm skeleton model they suggested. However, it is not so easy to estimate them because the identified stiffness parameters may frequently fall into a local solution by using the conventional least-squares method. In addition, although there exists the fact that the human joint system adjusts the joint stiffness with posture changes caused by some movement, the conventional method identifies the stiffness parameters as constants. Therefore, for estimating minute joint angle and joint displacement more accurately, this paper proposes a new method to identify stiffness parameters by use of a particle swarm optimization (PSO) method with taking into account such a human joint system characteristics. Consequently, it is shown that the proposed method can improve the fitting performance through the comparison between estimated values and experimental values obtained from CT images.

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A fall accident from a stepladder is often due to loss of balance while in a working posture. The purpose of this study was to evaluate posture stability, while standing on a stepladder, based on working posture and maximum reach distance. Ten male subjects reached forward as far as possible on a stepladder at shoulder height. The test involved combinations of 4 standing positions and 5 reach directions. The maximum reach distance on the horizontal plane, working posture, center of pressure (COP) location, and subjective assessment on posture instability were recorded. The horizontal distance from the center of a stepladder to the index fingertip was defined as the maximum reach distance, while COP location at these extreme distances determined the stability limit. The results showed that stability limit at two-steps below the platform was longer than that at one-step below the platform or on the platform. Maximum reach distance had no significant difference between on the platform and at two-steps below the platform. These results suggest that posture stability was improved at two-steps below the platform without a decrease of maximum reach distance.

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Although hazard perception training with accident videos is effective, accident videos can only be recorded by chance. It is impossible to carry out training which covers all desired points. To solve this problem, we created near-miss accident scenes by adding computer graphics to traffic recordings taken by experimenters during normal traffic situations on commuting route of participants. Eleven participants were recruited to evaluate the effectiveness of training using these scenes. Each of their vehicles was equipped with a drive recorder to document their driving behavior while commuting. After five round-trips, the participants took part in training utilizing these near-miss scenes. After training, five additional round-trips were recorded, and their driving behaviors before and after training were then compared. No significant differences were observed in driving speed; however, both duration and frequency of eye fixation at intersections along their commuting route were significantly increased.

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