In this paper, we propose a new formula for estimating optimal forest-road density, in which yarding resistance coefficient (k) was used to calculate the productivity. With this new concept, the major contributors to total working time, yarding time and construction time of road were expressed in functions of road density. Furthermore, the optimal forest road network density for minimum working time was obtained based on the power output of various machines. This formula revealed that forest road density tended to be extremely low when cable yarders and crawler forwarders had power output of less than 50 PS, and when wheel forwarders and tower yarders had less than 100PS output. Our calculations for tower yarders suggested that increasing product volume and decreasing inclination reduced the forest road density. These results showed that the formula was effective for the improving forestry operations.

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In the forestry industry, revenues must be balanced with expenditures to improve efficiency. One way of achieving this goal may be to mechanize reforestation and harvesting operations. An analysis of revenues and expenditures showed that to maintain a balance at an interest rate of 3%, expenditures for reforestation would have to be brought down to 50% of the present level of 1.8-3.6 million yen/ha. This assumes a harvesting cost (not including transport costs) of 5,000 yen/m^3 (average cost of clear cutting and thinning), which is possible at favorable locations under the present forestry conditions. For this purpose, prototype systems using self-propelled reforestation machines and mechanized harvesters were investigated for a hypothetical annual operating time of 500 hours. The results showed that increasing the annual operating hours of reforestation machines could reduce current costs by 30%, but the 50% goal was not attainable.

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We investigated the benefits of developing a circular forest road network, in which a patrol coefficient was introduced as a new index for showing network development. In this paper, patrol means traveling all roads at least once and return to the start point while minimizing the total driving distance. The patrol coefficient showed a close correlation with the ratio of circular roads to the total length of the network, and the sum of both values was found to be always at least 2. When the traffic benefit between two points was expressed using the traveling and direct distances, the benefit increased as the network was developed. While the points of greatest traffic benefits in networks were usually the start points, these benefits were not affected by the development of the network. This may have been due to the fact that topography made it difficult to construct roads connecting start points with other points on the network that were shorter than existing roads. The patrol coefficient is effective for evaluating the development process from non-circular roads into circular networks and for understanding the stage of development of circular forest road networks.

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