We analyzed the time-oriented and hierarchic characteristics of a road network in a watershed area using network analysis. Toei and Shitara towns (upper stream), Horai town (middle stream), and Shinshiro city (lower stream) in the Higashimikawa Forest Planning Area in Aichi Prefecture were chosen as our study areas. We compared their respective changes in the indices of network analysis from 1990 to 1999. In addition, the target values of the indices for connectedness were examined, and the road density required to achieve them was calculated. As a result, it was found that some of the forest roads constructed over the past 10 years were circular, and contributed to the development of the road-network. On the other hand, strip roads did not contribute much to their development, although the effects of the reduction of mean entire-forest access distance to the nearest road and the increase in circular roads were confirmed. The indices we used in this study changed significantly from the lower-stream toward the upper-stream areas, and we found that the characteristics of the road-network were affected by the process of determination of geographical continuity. The index α=20% was derived as the target value to develop road-networks, and the required road density was calculated to be around 4m/ha in mountainous areas.

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This paper examines the terrain conditions required for constructing a road on a ridge. The study areas included Kisodani, which had been investigated in the previous report, as well as the Iwaki and Tenryu Forest Planning Areas. Overall, ridge roads tend to be constructed in regions where the road density is high; this is because in mountainous areas, roads are constructed first at lower elevations and subsequently at higher elevations. In this manner, it is possible to reach a ridge by constructing a large number of roads. Our analysis showed that as the severity of terrain conditions such as slope angle, skewness of the slope angle distribution, relative height, and valley density increased, fewer roads were constructed on ridges. The conditions below some values had a slight influence on construction, but they had a greater effect on the maximum limiting values; for the slope angle, this was 20°, and for the relative height, it ranged approximately from 1,250 to 1,500m. There are hardly any ridge road constructions in regions with such terrain conditions. However in some regions, ridge roads have been constructed despite the steepness of the slopes. We believe that such roads were constructed by extending the roads from the neighboring basin across the ridge. It appears to be efficient to construct ridge roads in this way in regions which have severe terrain conditions.

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We conducted a realities analysis of a spur road network. Results are summarized as follow. 1) Slopes were divided into two categories: those with an inclination of less than 30 degrees, and those with an inclination of 30 degrees or more. Slopes of 30 degrees or more were parts of the surfaces of spur roads (3m wide with cutting height of 1.5m) that were filled in when the spur roads were constructed. Such slopes are officially classified as steep hillsides and measures are taken to prevent landslides and other disasters. In geomorphological terms, the inclination conversion line between the low-relief surface and the slope is called convex break of slope (erosion front). 2) At the study area in Shimanto-Cho, 52% of the total road network has been constructed on relatively gentle slopes of less than 30 degrees, which cover 35% of the area. Since road construction becomes more difficult at steeper inclinations,it is important to know where the gentler slopes are for road network development. 3) The results of compaction tests and road surface CBR values obtained in the present study indicated that steep hillsides in the area are composed of soil with a high tampability (that is, it becomes denser and harder when compacted). Thus, roads on steeper slopes are constructed by compacting and hardening the subbase. 4) It was concluded that compaction tests can be used to assess the soil of slopes that are targeted for regular road construction. However, in the case of spur road, construction plans should be evaluated based on the CBR value of the spur road surfaces.

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The functions of forest roads in forestry management were evaluated from the perspective of cut slopes. Areas within 150m of forest road sections were analyzed using GIS to identify slopes with heights below 1m, which can be approached directly by walking, and below 4m, where a swing yarder can be used in forestry operations. The distribution of artificial forests near the roads was dispersed. Land that could be accessed directly by walking constituted 40.8% of the area within 150m of forest roads. However, only 20.2% of directly accessible artificial forests were within 150m. The area where a swing yarder could be used constituted 79.1% of the area within 150m. However, this included only 35.3% of the plantation forests. It is clear that some forest roads are less functional, in terms of slope distribution and providing access to forest plantation resources near the roads.

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A mechanism for auto-landing operation of self-propelled carriage has been developed as an automation technique for one-man yarding. To achieve accurate auto-landing, it is necessary to accurately detect when the load that is suspended from a hoisting cable becomes a "no load" by landing. Therefore, we measured the load that was suspended on a hoisting cable based on the hydraulic motor pressure of the hoisting winch drive, and designed a technique for detecting the moment when pressure begins to decrease and the moment when there is "no load" from the viewpoint of easiness of remodeling and not ruining an original mechanism. When pressure reaches no load, the winch is stopped. In this method, there is little change in hydraulic pressure and detection becomes impossible when the load is light. Therefore, the boundary between correct and incorrect detection was calculated. The results of a corroborative experiment using an iron weight were roughly the same as the calculated values. The boundary value was about 100kg from a suspension height of 10m which, although a slightly large value, would be the range that the work can be done and could still enable automatic operation to be done accurately. Landing work that did not need a human worker became possible by combining this new method with an automatic unloading hook.

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