Another approach for calculating hours of machine use is to
use machine efficiency numbers reported by manufacturers in
ft3 or m3 of wood that can be handled per productive machine
hour of operation. Such efficiency numbers are affected by the
specific topography, tract size, and standing timber dimensions
on a site. For example, in a compendium for mechanized
harvesting equipment for Northwestern forests (Kellogg et al.,
1992), the productivity of a feller-buncher on gentle slopes (