In this study we aimed to evaluate the difficulty in going up and down the stairs and examined the eye movements while going up and down stairs or slopes.

In everyday life, we often use stairs. They have an important role to connect the different floors. But stairs with inappropriate size cause fatigue and even accidents in some cases. When people go up or down such stairs, they must be careful, namely, they need to look at each step or to go slowly. Consequently it is expected that the behaviour or reaction of human beings and difficulty in going up and down stairs have a certain relationship. We focused on visual information processing and analysed the eye movements while ascending and descending stairs.

In the experiment we used two types of stairs and one slope as the stimuli. One type of stairs almost satisfied the requirement of comfortable stairs and another type of stairs had an unusually large tread depth. In comparison with these two stairs, it was highly easy to go up or down the gentle slope used in this experiment.

Seven subjects participated in this experiment. They were instructed to go up and down the stairs or slope as usual.

The pattern of eye movements while going up and down stairs was common among the subjects. At the beginning, all the subjects paid attention to their own feet. Then the subjects moved their sight line in front of them. After that, they often looked at their own feet again. It means that they processed the visual information of the steps before they went up or down the stairs based on the result of the information processing.

The quantitative analysis showed that these movements differ in detail depending on the type of the stairs. For the stairs with large treat depth, the sight line moved mainly in the narrow area of the visual field. In the case of the stairs in normal size, the distribution of sight line was comparatively wide. However, it was common for these two cases, that all the subjects watched very often the steps. Especially when they went down the stairs, they watched the steps for longer time. In some cases, the subjects watched the steps for over 90% of the total time. On the other hand, when the subjects went up or down the slope, they looked often in front of them. In addition, the average viewing duration was longer, when the stairs were hard to go up or down. In such cases, the subjects needed more visual information of the stairs.

In this experiment it was confirmed that there was a clear relationship between eye movements and difficulty of the stairs to go up or down. It suggests that by using the data of eye movements it is possible to objectively evaluate the difficulty in going up or down the stairs.