This study used a questionnaire and interview survey to identify the characteristics and factors that increase the incidence (i.e., both frequency and possibility) of near accidents caused by log transportation drivers. Forty-five drivers belonging to one forest cooperative, three transporters, and one timber market responded to our survey. Most of the drivers had experienced near accidents, and 70% of them had experienced over three near accidents during the past three years. According to the findings, the highest frequency of near accidents occurred due to forest roads, while going straight, in curves, as sudden collisions with pedestrian/bicycle/car, and during log transportation. The factors that increased the possibility of near accidents were main work, size of the truck, and location of the road. Because the incidence of near accidents during log transportation has been increasing not only on forest roads but also on public roads, a range of measures are necessary to ensure public safety to reduce the incidence of these accidents. These include providing appropriate traffic signs, constructing parking spaces and rest areas for drivers, and improving traffic management at the intersections of forest and public roads.

In this study, we conducted a statistical analysis of the clogging of cross drainage ditches on 247 spur roads (1,298 locations) in the Shirasu area in southern Kyushu, which contains pyroclastic flow deposits from the Aira caldera. There are approximately three times more cross drainage ditches in the Shirasu than non- Shirasu areas. Until recently, clogging had not been a major concern despite a long time since ditch construction. The results indicate that clogging tends to progress abruptly approximately two years after construction and reaches nearly 100% after four years. A jam division of the cross drainage ditches was applied using the type-1 quantification method. Road access depends on the road age, topographical gradient around the ditches, geological conditions, and the road surface division. The standard maintenance time for cross drainage ditches is nearly three years in Shirasu and five years in non-Shirasu areas.

We investigated the possibility of employing specific site preparation methods, including an excavator bucket, grapple loader, and manpower, to control competing vegetation and reduce weeding. As a negative control, some sites did not receive external preparation. Site preparation with an excavator bucket and grapple loader respectively resulted in the lowest and second lowest (1) coverage, (2) maximum height of competing vegetation, and (3) suppression rate in planted trees. Additionally, the natural regeneration of woody plants as competing vegetation was reduced at the bucket- and grapple-prepared sites relative to the manpower-prepared and control sites. Even third year after planting, the survival rate of planted trees was high on the bucket- and grapple-prepared sites, whereas this rate had declined on the manpower-prepared and control sites. The average height of planted trees was relatively low on the bucket-prepared site as removal of the A₀ horizon suppressed the growth of planted trees as well as that of competing vegetation. Based on these results, it was possible to deduce the weeding schedule for each site preparation method. In continuous clear cutting and planting operations, reforestation costs (site preparation, planting, and weeding) were lowest when bucket-based site preparation was combined with the planting of bare-root seedlings. The costs were estimated to be reduced by approximately 50% compared to that of conventional operation.