Red and yellow - these extremely noticeable colors are used to paint heavy forestry machinery to prevent personal injury arising from careless contact with such machinery. However, attention must be given to the best color scheme that will be easily noticed by everyone at the work site. In this research, we examined the changes that aging induces in color perception. Color vision characteristics were calculated for regular (younger) and older (70 years old) persons using POKORNY's "Two-Factor Aged Eye Model" and compared color samples collected from painted forestry machines with environmental colors at actual forestry sites. The results showed that aged people tended to view colors as grayish or drab, especially yellows and blues. Bright colors were seen as subdued. However, there was little decrease in aged people's perception of red and orange, which should thus be useful as "key colors" in color design.

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Forest resource, slope, public and forest road layers of Geographic Information System (GIS) were obtained from a prefecture where a model area was located, in order to calculate harvesting costs of timber and forest biomass resources. Future forest resources at each stand were predicted using Richard's growth curves. Then, stand harvesting schedules were planned by balancing harvesting volumes of timber and forest biomass resources using random search while minimizing harvesting costs. This schedule will make it possible to supply forest biomass resources to an energy plant stably. The schedule will also be used to supply harvested timbers from the model area stably. Balanced harvesting forest biomass resources will be sufficient to supply electricity to 24.8% of houses in the model area. Fuel cost of electricity, 19.50 yen/kWh, was a little higher than the average electricity price in Japan, 18.17 yen/kWh. In order to use forest biomass resources as energy, it is necessary to reduce harvesting costs remarkably by developing forest road networks and machines for harvesting and transporting forest biomass resources efficiently.

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This paper deals with the development status of an omni-directional forest vehicle(TTM). The vehicle has three pairs of crawler undercarriages for proper grounding and stability in steep and rugged terrain. The heights of the three undercarriages can be controlled independently to maintain the vehicle level on slopes. Moreover, each crawler undercarriage is able to pivot-turn independently so that the TTM can change its moving direction motionlessly without turning the whole body. The TTM is able to climb a steep slope that a normal vehicle can not climb directly, by repeated traverse ascent and turnabout movement ("zigzag climbing"). According to the field test, the TTM was able to perform "zigzag climbing" on a grass covered slope of 35° and muddy skid trail of 28° while it was unable to perform direct climbing. According to the stability limit analysis of the vehicle's center of gravity, the TTM has sufficient stability when its height is properly controlled.

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