Upgrading of existing forest roads is a way of accelerating development of high-graded forest roads. However, the difficulty of upgrading in terms of physicality and economic efficiency　differs by conditions of location and structure of existing forest roads. Therefore, it is unclear how amount of development of high-graded forest roads could be achieved by upgrading. The purpose of this study is to clarify the possibility of development of high graded forest roads by upgrading existing forest roads by use of widening simulation. The simulation was performed for forest roads located in private forest of Ina city in Nagano prefecture, and the physical availability and unit cost of widening was resulted. As a result, the ratio of the total length of routes judged to be expandable under the set conditions to the total length of the existing low-standard road network was 89.0% in the case of the expansion to 3.5 m in full width and 70.1% in the case of the expansion to 4.0 m in full width. Average widening unit cost weighted road length is 1,787yen/m in case of widening to 3.5 m full width and 5,537yen/m in case of widening to 4.0 m full width. When all existing forest roads that able to widen to 3.5 m full width on study site, it is revealed that 36% of development amount needed to achieve objective development amount are covered by widening.

Although there is momentum to review forest roads as an alternative route during disasters, quantitative evaluation methods for their functions have not been sufficiently established. In mountainous regions, it is unclear how effective the role of forest road development is in building disaster prevention infrastructure. In this study, we developed a method to quantify the function of forest roads by improving the existing method for evaluating connection vulnerability to support the evaluation of public benefit from forest road projects. This study was conducted in Gujo City, Gifu Prefecture. Here, the function of alternative roads of forest roads was conceptually organized and a forest road with an alternative route function was defined as a forest road included in a set of non-overlapping routes (evacuation route set) that minimizes the time required while maximizing the number of non overlapping routes between evacuation origins and destinations. Furthermore, the evacuation route set could be obtained as a solution to the minimum cost-maximum flow problem between the starting and ending points. As a result of evaluating all evacuation route sets between the origins (225 evacuation centers in the city) and the destination (Gujo City Hall) in the study site, forest roads were included in the evacuation route set for ~65% of the evacuation centers. Thus, the proposed method can evaluate the alternative route function of forest roads only from the perspective of network topology and not from the perspective of disaster risk.

This study investigated the actual condition of skidding roads in clear-cut areas to provide information to support efficient and low-risk landslide clear-cutting operations. The survey was conducted in 63 clear-cut areas and the results showed that the average density of skidding roads was 361 m/ha, which was high, regardless of the ground slope of the clear-cut area. The study results in terms of average yarding distance, road layout, and the yarding method suggested that an excessive number of roads were established. This is because they did not contribute to the network development even though they were established at high density. Furthermore, 168 points of filling collapse were observed in the skidding roads, and the risk of filling collapse was very high on steep slopes with a slope of 30° or more. Several yarding roads were established in the steep slopes, and many roads were not easy to use continuously due to the filing collapse. Additionally, the percentage of forest land devastation related to skidding roads was large.

This study aimed to reveal the productivity of uphill yarding during final cutting using a medium-range tower yarder. Thus, final cutting operations in a coniferous artificial forest on steep terrain were observed and working time were analyzed. The operational system comprised four people; a harvester operator who operated carriage on the strip road, and a chainsaw-man, a carriage operator, and a choker-man in the forest. At a mean yarding and lateral distance of 137.5 ± 5.0 m and 15.0 ± 5.2 m, respectively, the operating time was 11,729 s, the number of yarding cycle was 31, the yarding stem volume was 30.9 m³, and the processing log volume was 29.2 m ³ . Consequently, the cycle time of 378.4 s/cycle, the mean loading volume of 1.00 ± 0.23 m ³ /cycle, the yarding productivity of 9.0 m ³ /hour, the labor productivity from cutting, yarding, and processing, were calculated at 2.2 m ³ /labor-hour. Following the analysis of working time for thinning from a previous study and final cutting from this study, the prediction formula of yarding operation as variables of yarding and lateral distances was derived, and the productivity of uphill yarding during final cutting for an assumed loading volume was predicted. Thus, this tower-yarder system could yield higher productivity during final cutting and thinning.

Log production is increasing as mature forest resources increase, operation areas expand, and forest machinery advances. The material processing status and sales performance in the log production process are essential forestry management information; however, such information is rarely applied. Here, we examined lumber data recorded at the logging site to analyze stem-curve equations of felled trees and assessed the lumbering method, calculating the average log sale price from the material sales records. Based on these data, we produced standard log sizes, stem shapes, and simplified log patterns of the experimental forests. The results of trial calculations of the volumes and sales amounts of the material production site using a model indicated a high consistency of calculations with actual sales results.

This study analyzes the relations between the incidence of occupational accidents and the age of workers. The incidence of occupational death accidents and injury accidents was calculated using age, cause and type of accident from occupational accident database from 2010 to 2015. Although the incidence of death accidents of 60-year-old individuals or older was the highest, statistically significant differences by age were not shown. The incidence of injury accidents under the age of 20 is higher than other ages. The high incidence of injury accidents under the age of 20 was a cut wound caused by a chain saw and a fall on the ground. If the incidence of individuals under the age of 20 reduces, the number of injury accidents in forestry will be reduced by approximately 3%. This number will be lower than the goal established in the 13th Occupational Safety & Health Program by the Ministry of Health, Labour and Welfare. Because the incidence of injury accidents caused by a fallen tree is high for all ages, it was effective for goal achievement to reduce injury accidents caused by a fallen tree in addition to reducing a characteristic injury accident as regards individuals aged 20.